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C ELL D IVISION Chapter 6

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C ELL D IVISION

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Before cells can divide, DNA has to replicate itself so there are 2 copies

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DNA R EPLICATION DNA strand opens up and DNA polymerase attaches The exposed unpaired bases find new partners Growth of the DNA replicates is always in one direction This means while one side can grow as the DNA unzips The other side grows in pieces that then must be glued together Errors are edited

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T ELOMERES TICKING CLOCK Hutchinson-Gilford Progeria Syndrome

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M UTATIONS Sometimes the errors result in proteins that dont work or dont work as well What causes a mutation? Spontaneous Radiation-induced mutations Chemical-induced mutations Sphinx mutation

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A NIMAL CELLS HAVE COUNTERS THAT KEEP TRACK OF HOW MANY TIMES A CELL HAS DIVIDED. T HESE COUNTERS ARE CALLED : A) odometers. B) telomeres. C) chromosomes. D) nuclei. E) centromeres.

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I N DNA REPLICATION, WHEN THE DNA MOLECULE SEPARATES INTO TWO STRANDS : A) it is possible to reconstruct perfectly all the information on the missing strand because one strand carries all the information needed to construct its complementary strand. B) the rebuilding process begins, in which an enzyme connects the appropriate complementary base to the exposed base. C) the mitotic phase of cell cycle begins. D) All of the above are correct. E) Only a) and b) are correct.

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W ITHIN INTERPHASE, WHICH OF THE STAGES IS DEFINED BY THE ACTIVE REPLICATION OF THE CELL S GENETIC MATERIAL ? A) the Gap 2 phase B) the mitotic phase C) the Gap 1 phase D) the replitosis phase E) the DNA synthesis phase

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2 D IFFERENT F ORMS OF C ELL D IVISION Asexual reproduction and cell division of body cells Prokaryotes and some single celled Eukaryotes Binary fission All growing or repairing multi-cellular organisms Mitosis Sexual reproduction Some single celled Eukaryotes Conjugation Eukaryotes Meiosis

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D IFFERENT F ORMS OF C ELL D IVISION Asexual reproduction and cell division of body cells Prokaryotes and some single celled Eukaryotes Binary fission All growing or repairing multi-cellular organisms Mitosis *** Sexual reproduction Some single celled Eukaryotes Conjugation Eukaryotes Meiosis ***

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M ITOSIS 2 cells Identical to Parent

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T HE PURPOSE OF MITOSIS IS TO ENABLE EXISTING CELLS : A) to generate gametes. B) to grow. C) to die on purpose. D) to generate new, genetically identical cells. E) to generate new, genetically diverse cells.

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L ET S SEE THAT AGAIN - M ITOSIS End with 2 cells that are genetically identical to the parent and to each other.

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T HIS FIGURE DEPICTS : A) mitotic anaphase. B) mitotic prophase. C) mitotic metaphase. D) mitotic telophase. E) meiotic anaphase I.

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S EXUAL R EPRODUCTION & M EIOSIS What would happen if these cells were formed by mitosis?

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M EIOSIS - A GAIN Only during the formation of eggs or sperm Two divisions in one At start homologous chromosomes with their replicates come together to form a tetrad (4) Genetic recombination First division homologous chromosomes separate Second division replicates separate End up with 4 cells that are all genetically different

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= Oogenesis Spermatogenesis produces 4 cells all the same size that then go on to lose most of the cytoplasm and get a tail for swimming.

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G ENETIC R ECOMBINATION THE REASON FOR S EX

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P ROJECT 3 Use the hand out or compare figures 6-11 and 6- 20. List all of the features that the two forms of division have in common and explain these. List all of the features found only in meiosis. Explain your answers. You may work in groups to develop your lists, but hand in your own write-up either at the end of class or at the start of the next class period.

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K ARYOTYPE

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W HAT IS DIFFERENT ABOUT THIS KARYOTYPE ?

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D OWN S SYNDROME

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Why are only smaller chromosomes ever seen in trisomy?

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W HICH OF THE FOLLOWING ARE FEATURES THAT DISTINGUISH CANCER CELLS FROM NORMAL CELLS ? A)Normal cells undergo cytokinesis; cancer cells do not undergo cytokinesis. B) Normal cells have contact inhibition; cancer cells have no contact inhibition. C) Normal cells metastasize; cancer cells do not metastasize. D) Normal cells can divide a finite number of times; cancer cells can divide indefinitely. E) Both b) and d) are correct.

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A DIPLOID (2N) CELL UNDERGOES MEIOSIS. W HAT ARE THE PRODUCTS OF THIS DIVISION ? A) one polyploid gamete B) four haploid cells C) four diploid cells D) two haploid cells E) two diploid cells

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T HE EGG CELLS OF A HORSE CONTAIN 32 CHROMOSOMES. H OW MANY CHROMOSOMES ARE IN THE HORSE S LIVER CELLS ? A) 32 B) 16 C) 128 D) 64 E) 8

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R EAD CHAPTER 7 ON I NHERITANCE OF T RAITS