midterm answer key

midterm answer key - EEB 13 Midterm Exam, 7 Feb 2008, p. 1...

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EEB 13 Midterm Exam, 7 Feb 2008, p. 1 name: (12) You are a genetic counselor. A couple comes in to say that although neither of them has the Tay-Sachs genetic disease, they are both carriers of the trait. They want to have children and want to know what proportions of possible kids would (a) have the disease, (b) be a carrier like themselves, or (c) be normal - not have the disease or be carriers. Because you know that Tay-Sachs is a completely recessive trait ( t ) compared to the normal gene ( T ), use a Punnett square diagram to show how the trait would be inherited to their offspring. What are the genotype(s), phenotype(s) and proportions of the possible offspring? T ½ t ½ T ½ TT ¼ Tt ¼ t ½ Tt ¼ tt ¼ genotypes: TT Tt tt phenotypes: normal carrier disease proportions ¼ ½ ¼ [or, TT + Tt = both normal, and proportion = ¾] ( 8) Genetic variability among genotypes is necessary for evolution to occur by natural selection. What process did Charles Darwin think was the source of this variability? mutation What process do we now know is the major source of this variability? recombination Name and briefly define or describe two (of five possible) things that happen during reproduction that increase variability among genotypes: 1. sexual reproduction itself: N(mom) + N(dad) = 2N(offspring) 2. independent assortment of maternal and paternal chromosomes in meiosis 3. crossing over between homologous chromosomes during tetraploid stage of meiosis 4. random union of gametes 5. pattern of mating: random mating, inbreeding or outbreeding
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EEB 13 Midterm Exam, 7 Feb 2008, p. 2 name: (16) Matching: From the following list of numbers, place in the blank the number appropriate
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midterm answer key - EEB 13 Midterm Exam, 7 Feb 2008, p. 1...

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