Series: Biology Review

Smiles

09/23/2009

~ Jared

I just watched this as a review for a physiology class. I have taken a semester of genetics already and had this stuff down pat but it has been awile since I have used the info. This was an excellent review and in ten minutes I feel like i can remember so much from my last class. Great teacher. I wish he had stuff to cover all my review needs!

Mitosis vs Meiosis

04/06/2009

~ thomisha

Great insight, easy and fast learning skills.

Below are the descriptions for each of the lessons included in the series:

• Biology: The Eukaryotic Cell Cycle

  Professor Wolfe gives an overview of the full cycle of eukaryotic cells. There are consistencies in the cell cycles of almost all eukaryotic cells. Why do cells divide? All the cells divide to maintain their volume to surface are ratio. When cells divide, the genetic information in the offspring cells must be identical to the genetic information in the parent cell, so this genetic information must first be organized and doubled. This process is called 'packing' and forms chromasomes, which are 2 molecules of identical DNA. Ninety percent of a cell's life cycle is spent in the period called "interphase," which is where the cell grows (known as the G1 or Gap 1 phase), DNA replicates (known as the S phase for DNA synthesis), and the cell prepares to divide (known as the G2 or Gap 2 phase). A eukaryotic cell will only spend ten percent of its life cycle dividing, or "replicating."

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: Mitosis: The Phases

  In this second Mitosis lesson, Professor Wolfe adds in the terms for the phases of Mitosis. He begins with a quick review of chromatins, chromosomes, and chromatids, and then introduces the five phases of mitosis, which are prophase, prometaphase, metaphase, anaphase, and telophase. Professor Wolfe explains each phase in depth, showing images of example cells and pictures of actual cells to help you understand. Throughout the process, centrosomes start to seperate and the cell forms sister chromatids, the nuclear envelope breaks down, chromosomes line up along the center of the cell, chromosomes seperate, a cleavage furrow forms, and the cell begins to divide.

  This lesson is perfect for review for a CLEP test, mid-term, final, summer school, or personal growth!

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: Cytokinesis

  Cytokinesis is the division of the cytoplasm that takes place after mitosis, producing two daughter cells. Professor Wolfe walks you through this process in both animal and plant cells. In an animal cell, the well membrane elongates due to the contraction of microfilaments actin and myosin. This contraction creates a cleavage furrow that will eventually produce two separate cells known as daughter cells. In plant cells, the same process isn't possible, because of the rigid, non-cleavable cell wall. The Golgi apparatus in plant cells actually migrate to the middle of the cell, where they synthesize a new cell membrane. Then, proteins from the golgi vesicles are able to synthesize a new cell wall, creating two distinct cells.

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: Watson and Crick: The Clues

  Professor Wolfe explains the history behind the discovery of the strucutre of DNA. Molecules are too small to observe, and this means it was impossible to determine the molecular structure of DNA. In 1950, Franklin and Wilkins used X-ray defraction to create images of DNA, exposing a possible helical structure. They also determined 3 repetitive ratios, 0.34, 3.4, and 2.0, but did not know what these represented. This information was used by Watson and Crick to develop the first accurate approximation of the structure of DNA. They began with the belief that the structure was a double-helix and used molecular models, to piece together the structure. Watson and Crick discovered that the 0.34 nm number was the distance between each nucleotide, and the 3.4 nm number was 10 nucleotides. The 2.0 nm number they determined to be the diameter of the helix. They also discovered that purines and pyrimidines created a hydrogen bond across the double-helix. Using these dimensions and information, they created the model of DNA that has become the foundation for molecular genetics.

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: Independent Assortment

  This lesson covers the concept of independent assortment. This is a critical idea for the tracking of genes and heredity with the help of the idea of meiosis. Tracking genes on chromosomes through meiosis can tell us something about genetics. Homologous chromosomes are chromosome pairs that contain genes that control the same traits. Homologous chromosomes can assort independently of other pairs of homologous chromosomes. This concept is called 'independent assortment' and it leads to many possible combinations of chromosomes in gametes and offspring.

  The lesson will also explain how disjunction (the separation of homologous chromosomes) further contributes to the number of different chromosomal combinations or outcome possibilities. The combination of synapsis and disjunction occur and create independent assortment, which allows for drastically different trait combinations. The more pairs of chromosomes an animal has, the more possibilities there are for possible combinations of traits and chromosomes in offspring.

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: Protein Synthesis: An Overview

  Professor Wolfe provides an overview of the process of protein synthesis. Protein synthesis occurs when a ribosome bonds to mRNA in the cytosol of the cell and has four steps, initiation, elongation, termination and translation. Initiation begins when the start codon binds with the initiator tRNA at the P site. Elongation begins once the second tRNA anticodon binds with the appropriate mRNA codon at the A site. GTP provides the energy that is needed to form the peptide bonds that hold the polypeptide chain together. Termination occurs when the mRNA stop codon binds with a release factor. Translation results in the release of the new polypeptide chain.

  This lesson is perfect for review for a CLEP test, mid-term, final, summer school, or personal growth!

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: Transcription and Translation Overview

  To understand transcription and translation, Professor Wolfe states that you must first understand the "central dogma" that DNA makes RNA and RNA makes proteins. But how is this infromation communicated? Through transcription, which is the process where DNA information is coded into RNA, and translation which is the process of converting the mRNA molecule by ribosome into polypeptide strand. This process happens in both prokaryotic and eukaryotic cells, but in Eukaryotic cells translation takes place outside of the nucleus. Professor Wolfe also discusses the three different types of RNA, mRNA, tRNA, and rRNA. He explains rRNA and how is used to help translate the mRNA.

  This lesson is perfect for review for a CLEP test, mid-term, final, summer school, or personal growth!

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: Meiosis: Prophase I

  In this lesson, Professor Wolfe starts to discuss the individual phases of meiosis, which are very similar to the phases of mitosis. Meiosis, however, requires two cell divisions because of the creation of haploid cells from the sister chromatids. Ninety percent of meiosis occurs in the first phase, known as Prophase I. In this phase, two very important events occur. The first is the formation of a tetrad through the process of synapsis. Synapsis is the pairing of homologous chromosomes, which form the tetrad structure. These tetrads create areas called chiasmata (chiasma, if singular), where homologous genetic material "crosses over," or is exchanged. This exchange of homologous genetic information will be very important in further study of meiosis.

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: Mitosis: An Overview

  Mitosis seems to be a sticking point for many biology students. In this lesson, Professor Wolfe simplifies the concept of mitosis by breaking it down into the functions and forgoing the vocabulary (for the time being). He begins with a review of the eukaryotic cell cycle. DNA is only packed into chromosomes when a cell is going to do mitosis. A chromosome is two identical strands of DNA connected by a centromere. The centromere includes a section called the kinetochore. During mitosis, the nucleus of the cell splits and then the chromosomes form. The mictrotubiles connect to the kinetochrome and allow for chromosomal movement and division.

  This lesson is perfect for review for a CLEP test, mid-term, final, summer school, or personal growth!

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: Disjunction and Meiosis II

  In this lesson, Professor Wolfe starts out with an overview of Meiosis and then discusses and explains the processes of both Meiosis I and Meiosis II. During the stages of meiosis I, homologous chromosomes pair and are segregated into separate cells. These stages include prophase I, metaphase I, anaphase I and telophase I. Professor Wolfe will explain what happens durring each of these different phases. He will focus specifically on what is happening with the cell's chromosomes during these phases. In prophase I, homologous chromosomes synapse and form tetrads. In metaphase I, homologous chromosomes organize and line up. In anaphase I, homologous chromosome pairs separate, and in telophase I, a cleavage furrow forms, creating two cells. Each created cell has one chromosome from each homologous pair.

  During the stages of meiosis II, the doubled chromosomes are divided and move into separate cells as in mitosis. Meiosis II is also made up of stages (prophase II, metaphase II, anaphase II and telophase II), and you will also learn what happens in each of these phases, again with a focus on what is going on with the chromosomes. In prophase II, the nuclear envelope breaks down and spindle fibers form. In metaphase II, chromosomes line up on the metaphase plate. In anaphase II, chromatids separate, and in telophase II, haploid cells are eventually created. After meiosis II there are four cells, each containing the haploid genetic complement. This is the objective of Meiosis: to reduce the number of chromosomes by half (to form haploid cells) and to segregate homologous chromosomes.

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology:DNA Polymerization-Triphosphate Nucleotide

  Meselson and Stahl determined that DNA is replicated using the semi-conservative method, which means that the DNA opens down the middle, and each side acts as a template for the new strand. But this answer only produces more questions. How does the polymerization of the new strand of DNA happen? Polymerization is an endemic process (meaning it requires energy), and not spontaneous. It also required joining of the sugar-phosphates, in addition to the nucleotides. Finally, it requires an enzyme, known as DNA polymerase. Professor Wolfe explains how triphosphate nucleotides make the polymerization process possible. These triphosphate nucleotides float freely within the nucleus of the cell, and each DNA base exists in a triphosphate nucleotide form. The energy that is released by the breaking of the triphosphate bond is what provieds the energy for the polymerization of DNA.

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: Oogenesis: Meiosis in Females

  In this lesson, Professor Wolfe reviews meiosis in the female system. In meiosis, a somatic cell (2n) goes through two splits to become gametes. Gametes are generated in organs called gonads. Meiosis is the division of a diploid cell to form a haploid cell called a gamete. Meiosis in a female is referred to specifically as oogenesis. It takes place in the ovaries of a female human. He will walk through the steps of female meiosis, including both Meiosis I (which creates secondary oocytes and polar bodies, which are degenerative and non-functional) and Meiosis II (a process that only occurs at fertillization in the production of offspring). If fertilization occurs (and a zygote or fertilized egg is created), Meiosis II happens and in that second division, a secondary oocyte is divided into a second polar body and an ovum. The ovum (n) will have half of the number of chromosomes as the oogonium (2n).

  He also highlights the main differences between female and male meiosis processes (differences between oogenesis and spermatogenesis) as well as the explanation for why polar bodies are created in oogenesis.

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: Sexual Reproduction and Role of Meiosis

  There are two types of reproduction, asexual reproduction and sexual reproduction. Asexual reproduction creates genetically identical offspring. Several types of asexual reproduction are binary fission, which occurs in bacteria, budding, which occurs in coral, and spores, which some plants produce.

  However, sexual reproduction is selected for, genetically. This is because sexual reproduction produces new genetic combinations in offspring that allow for more variety and competition. These genetic combinations are known as recombinant genes. However, sexual reproduction requires a reductive cell division, called meiosis, to produce gametes. Gametes are haploid sex cells, instead of the normal diploid somatic cells and are necessary to keep the correct number of chromosomes in DNA.

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: Mitosis vs. Meiosis

  In this lesson, mitosis and meiosis are compared in terms of DNA replication, the number of divisions, the presence of synapsis, the number of daughter cells, and the numbers of chromosomes in the products and function. This lesson is a good overview of both meiosis and mitosis, and explanation of why they are important and an analysis of how they are similar and different. Professor Wolfe reiterates, "Meiosis->Gametes; Mitosis->Everything Else."

  From a similarity standpoint (between meiosis and mitosis), in both: DNA is replicated and the process consists of phases (prophase, metaphase, anaphase, telophase). On the flip side, Meiosis and Mitosis differ along the following dimensions: number of divisions (1 for mitosis and 2 for meiosis), synapsis is only a characteristic of meiosis (in prophase I), the number of daughter cells produced varies (4 non-identical haploid cells in meiosis and 2 identical cells in mitosis), the number of chromosomes in resulting cells varies (2N in mitosis to match the original parent cell and only N in meiosis as the resulting cells are haploid), and the function/objective of the processes vary (somatic cells are produced via mitosis and gametes are produced by meiosis).

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: Homologous Chromosomes

  Professor Wolfe proposes two problems that have to be overcome during meiosis. One problem is that offspring have to have the same number of chromosomes as the parents, which means that the cells used in sexual reproduction need to have half the number of chromosomes as normal somatic cells. This means that meiotic division has to produce haploid cells.

  The second problem is the sorting of chromosomes. Each offspring will have to have not just the correct number of chromosomes, but also all the correct types of chromosomes. These two problems can be overcome by understanding that humans don't just have 46 chromosomes, but 23 pairs of chromosomes. A diploid cell is a cell with two copies of each chromosome. Sexual reproduction uses homologous chromosomes, which are chromosome pairs that have the same genetic composition but are derived from different parents.

  This lesson is perfect for review for a CLEP test, mid-term, final, summer school, or personal growth!

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: DNA Replication: A Summary

  In this lesson, Professor Wolfe provides a complete overview of the replication of DNA, beginning with its structure. DNA has a double-helix structure of nucleotides, which made-up of a sugar, a phosphate, and a base. The strands are antiparallel, meaning they run in opposite directions, known as the 5' strand and the 3' strand. DNA replicates by the semi-conservative method of replication.

  Professor Wolfe explains how DNA polymerase only reads in one direction, from 3' to 5', and therefore creates ""replication bubbles"" in order to replicate the DNA twice as fast. This creates leading and lagging strands, which require RNA primer and Okazaki fragments added to the lagging strand in order for the process to work properly. At the end of the strands, which lack the free OH molecule needed to complete the process, telomeres are used to protect against a loss of information.

  This lesson is perfect for review for a CLEP test, mid-term, final, summer school, or personal growth!

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: Watson and Crick: The Double Helix

  In 1953, Watson and Crick published their findings on the structure of DNA in the journal Nature. Knowing the structure of DNA allows us to understand how it works in the body. Professor Wolfe furhter explains their findings and how measurements from the X-ray defraction image helped define the structure of the DNA. These are the 0.34, 3.4, and 2.0 measurements that were observed in the image, but not understood. He also explains the bonding between the purines and pyrimidines. These are hydrogen bonds, formed in the middle of the double-helix. The sugar-phosphate chains are antiparallel. Finally, Professor Wolfe explains the four requirements of DNA, that it is informational, capable of replication, capable of communicating with cells, and capable of change, and how DNA meets all of these requirements.

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.
  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: Spermatogenesis: Meiosis in Males

  This lesson covers the biological explanation of how sperm is created. It discusses both meiosis in the male that create sperm (spermatogenesis) and an explanation of why sperm are structured as they are and a description of where each of these processes take place anatomically. Additionally, there is a discussion of how developing sperm cells receive nurtrients. Sperm are produced in the seminiferous tubules of the testis. These tubules are arranged in layers that parallel the stages of meiosis.

  Germ cells produce primary spermatocytes which divide to produce secondary spermatocytes, which divide to produce spermatids, which develop into sperm. The process of sperm creation is called spermatogenesis. It is basically the type of meiosis that occurs in males (where oogenesis is the type of meiosis that occurs in females). Meiosis is the division of a diploid cell (has a diploid number of chromosomes) into 4 haploid cells (gametes). In the process of spermatogenesis, a diploid cell sees a doubling of chromosomes and then is divided into two separate diploid cells in Meiosis I. Following this is a second division in which the outcome is four cells with exactly half of the number of chromosomes as there were in the original cell that divided in Meiosis I.

  Last, Professor Wolfe will explain why men don't 'run out' of sperm cells while women do run out of eggs during the course of their life (because the germ cells that go through meiosis to create sperm also can undergo mitosis, or cell division, to reproduce though the equivalent cells in women cannot undergo mitosis).

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

  George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science.

  Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel.

  His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp.

  He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

• Biology: Replication: Meselson and Stahl

  Watson and Crick also proposed a possible method of replication, which is a requirement for genetic material, in their article. This method, called the semi-conservative method, was just proposed, though, and untested. Meselson and Stahl devised a method to test the replication. There are three types of possible replication methods, conservative, semi-conservative, and dispersive. Professor Wolfe explains these three types of replication and the method of adding isotopes to bacteria that Meselson and Stahl used to test replication. He compares and contrasts the expected outcomes of each type of replication with the actual outcome that Weselson and Stahl found. This testing confirmed the semi-conservative method f DNA replication.

  Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.