bio 105 Midterm

bio 105 Midterm - 1 Sample Genetics Exam Questions from...

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1 Sample Genetics Exam Questions from Past Years KEY Question 1) (6 points) Consider a loss-of-function mutation in a haplo-sufficient gene. Circle the correct choice in each bold section below: The mutation would be (dominant or recessive) Heterozygous individuals bearing a mutant allele and a non-mutant allele would (display or not display) the mutant phenotype. The mutant allele (could or could not) be a wild-type allele in the population. Question 2) (8 points) The A and B genes are on different chromosomes and affect different traits. A and B are the dominant alleles, and a and b are the recessive alleles. a) (4 points) A/a; B/b individuals are test crossed. What percentage or proportion of the offspring will display both recessive phenotypes? (1/2 a) (1/2 b) = 1/4 b) (4 points) Now add the C gene. A/a; B/b; C/c individuals are mated with A/a; b/b; C/C. What percentage or proportion of the offspring will be A/a; B/b; C/c? (1/2 A/a) (1/2 B/b) (1/2 C/c) = 1/8 Question 3) (5 points) Your neighbor has a field of lovely white, yellow, and orange flowers. He mates 2 yellow-flower plants with each other and is surprised to see the production of all 3 colors in the F1 generation. a) In all your genetic wisdom, you explain to your neighbor that this is a single-gene trait and is an example of: incomplete dominance b) If you count the F1 flowers, what proportions of the different colors would you expect? 1 white : 2 yellow : 1 orange
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2 Questions 4) (11 points) The following pedigree shows the inheritance of a rare single-gene disorder. I-1 I-2 A/a A/a II-1 II-2 II-3 II-4 II-5 a/a A/- A/A A/A a/a III-1 III-2 A/- A/a IV-1 a) (3 points) Does this appear to be a dominant or recessive disorder? Explain briefly. Recessive 2 unaffected parents had an affected child disorder skips generations b) (4 points) Fill in the genotype of each individual in the pedigree. You can assume that spouses who married in and whose genotypes are uncertain were homozygous for the wild-type allele. Be sure to define your symbols. c) (4 points) What is the probability that child IV-1 will have the disorder? (Show your calculations, to receive partial credit.) (2/3 that II-2 is A/a) (1/2 that III-1 is A/a) (1/4 that child is a/a) = 1/12 Question 5) (4 points) You have been hired as Brother Gregor’s gardening assistant. He has several different patches of peas. Each patch is true-breeding and shows a single recessive trait. He points to his recessive white-flower patch (purple is dominant) and his recessive green-pea
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bio 105 Midterm - 1 Sample Genetics Exam Questions from...

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