problem set 5 answers

problem set 5 answers - Problem Set #5 Covering Chapters...

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Problem Set #5 Covering Chapters 13, 14, 15 &16 of BIOLOGY BILD1 Wi08 Problem 1. A. Yes, the two daughter cells at the end of mitosis are genetically identical. They started out diploid and at the end each have two complete sets of the genome, making them diploid, or 2n, just like the original cell. Each daughter cell has two copies of all chromosomes. As this particular cell has two chromosomes, then the total number of chromosomes in the cell is 4. B. The microtubules-spindle complex is involved in all of mitosis, especially metaphase and anaphase. Microfilaments are primarily used at the very end of mitosis during cytokinesis. C. At the end of meiosis II, the four gametes are genetically distinct from each other. Due to homologous recombination and independent assortment of chromosomes, each gamete is at least slightly different from the next. All gametes have received one copy of each chromosome, so they are haploid (1n). D. During Prophase I, the homologous chromosomes must pair up with each other. When the homologs are next to each other synapsis can occur. The arms of the chromosomes intertwine and form chiasma. Finally, special enzymes come in and complete the crossing- over event, giving rise to new recombinant chromosomes. The enzymes that actually cut and paste the DNA in this homologous recombination are very slow, and it is very important that they do not cut or paste the wrong pieces, so their work takes a long time. Therefore, the slowest step is Prophase I. E. Metaphase I separates homologous chromosomes from each other (ie. IA from IB). Metaphase II separates sister chromatids from each other. This is most similar to the process seen in Metaphase of mitosis. Compare the drawings of meiosis to your textbook, to those drawings of Mitosis. Page 1 of 9
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Problem Set #5 Covering Chapters 13, 14, 15 &16 of BIOLOGY BILD1 Wi08 Problem 2: Page 2 of 9
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Problem Set #5 Covering Chapters 13, 14, 15 &16 of BIOLOGY BILD1 Wi08 Problem3: A. Haploids only have one copy of any given gene, so they can never be heterozygous. Without the interaction between the two alleles in one organism, no determination can be made of which is dominant and which is recessive. B. When homologous chromosomes line up on the metaphase I plate, they do it randomly. If you have copy A and copy B of every chromosome, there is no rule directing all A’s to go Page 3 of 9
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Problem Set #5 Covering Chapters 13, 14, 15 &16 of BIOLOGY BILD1 Wi08 right and all B’s to go left. It is a mix and match system and you can end up with any combination of A’s and B’s in a gamete. This is called Independent Assortment, meaning the homologous distribute randomly between the forming gametes. If there are genes on two different chromosomes, they will also appear to assort independently because of the random chromosome separation. C. Locus: The gene location on a chromosome
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This note was uploaded on 04/28/2008 for the course BILD BILD 1 taught by Professor Bever during the Winter '08 term at UCSD.

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problem set 5 answers - Problem Set #5 Covering Chapters...

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