quiz6 key

quiz6 key - AGRY 320 GENETICS Spring 2011 April 22, 2011...

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Unformatted text preview: AGRY 320 GENETICS Spring 2011 April 22, 2011 QUIZ #6 NAME ______________________________________________ Carefully read the material and the instructions and answer the questions. Feel free to use the back of this page to perform work so that you can clearly place your answers in the spaces provided. Answer the questions by circling all of the correct or the most likely correct answers. Chromosome Rearrangements (5 points each question) 1. A marigold breeder is working with two simply inherited genes (fc and R). These genes normally segregate independently. However, after making a cross with an Australian variety, he finds that the F1 of that cross are semi-sterile and that fc-R recombinant types are always absent. Which of the following is the most likely explanation for this result (circle the correct answer): a. Australia is in the southern hemisphere. b. There has been a duplication of the disease resistance gene. c. Plant diseases in Australia are different from those in the U.S. d. The Australian marigold has a chromosome inversion on the chromosome that carries the flower color and disease resistance genes. e. There has been a deletion of the flower color gene in the Australian marigold. 2. The term autopolyploidy refers to polyploids that originated from a duplication of chromosomes within a species. True or False 3. Reciprocal translocations are visible during metaphase I as tetravalents. (Circle the correct answer) True or False 4. A friend of yours tells you that some watermelons have 22 chromosomes, and that other watermelons have 44 chromosomes, and that crossing the two types produces seedless watermelons. In response to this statement you make the following correct comment (circle that answer)a. That could be true. If the haploid chromosome number is eleven, the F1 plants would be triploid (3n=33) and the odd chromosome number might cause euploid seeds that spontaneously abort as they develop. b. That is impossible. Seedless watermelons come from seedless watermelon seeds. c. That could be true. If the haploid chromosome number is eleven, the F1 plants would be triploid (3n=33) and the odd chromosome number might cause aneuploid seeds that spontaneously abort as they develop. 5. The following are characteristics of most balancer chromosomes (circle all of the correct answers): a. They carry either a homozyogous lethal or a homozygous female-sterile mutation. b. They carry one or more chromosome inversions and a dominant visible mutation. c. They permit one to easily make a line that is completely isogenic for a single chromosome. 6. Which of the following chromosome rearrangements can result from unequal recombination (mistakes in crossing over): a. duplication b. deletion c. transposition d. Robertsonian fusion Hardy-Weinberg Equilibrium (Population Genetics) 6. (10 points) Which of the following conditions are assumptions that must be met for alleles to be present in H-W equilibrium (circle the correct answers). a) assortative mating b) hybrid vigor c) no migration d) no selection e) small population 7. In a certain population, Cystic fibrosis is a recessive condition that affects 1 in 2,500 (0.04%) babies. Assuming this trait is in H-W equilibrium, a) (5 points) what is the frequency of the cystic-fibrosis-causing allele (mutation) in the population? Frequency of a is q. Frequency of a/a = q2 = 1/2500 (0.04% or 0.0004) q = √0.0004 = 0.02 or 2% b) (5 points) what is the frequency of the individuals that are carriers (heterozygous) for the cystic fibrosis mutation in the population? Frequency of heterozygotes = 2pq q = 0.02 p+q=1 p = 1 – q = 1 - 0.02 = 0.98 2pq = 2(0.98)(0.02) = 0.0392 or 3.92% ...
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This note was uploaded on 02/26/2012 for the course AGRY 320 taught by Professor Stewert during the Spring '09 term at Purdue.

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