A few example questions from last year’s Midterm #2

Here are a few questions from last year’s Midterm #2 to help with your studying.  Answers will appear on the blog in a few days.

#7. (3 points) In domestic cats, an X-linked gene influences coat coloration. One allele results in black coloration and a second allele causes orange coloration. Female cats with both black and orange spots are heterozygous at this X-linked locus. What is the explanation for this genotype-phenotype relationship?

a) Incomplete dominance

b) Codominance

c) Epistasis

d) Dosage compensation


#13. (3 points) A genetic distance of 0.01 cM corresponds to what recombination frequency?

a) 1

b) 0.01

c) 0.001

d) 0.0001


#20. (6 points) Cyclins and cyclin-dependent kinases (CDKs) form heterodimers that function to regulate the cell cycle. Briefly describe the specific, molecular function played by cyclins in this process, as well as the specific molecular function of CDKs.


#21. (6 points) You are studying three linked genes: D, E and F. There are two alleles for each gene (D and d, E and e, F and f). E is the gene in the middle. The genetic distance between D and E is 0.5 cM. The genetic distance between E and F is 10 cM. You perform a cross between a triply heterozygous organism and a triply homozygous recessive tester and analyze 10,000 progeny.   Among the progeny, only two double-recombinants were observed. What is the degree of crossover interference (i)?

Hint:   i = 1 – (coefficient of coincidence)

= 1 – (obs. # double recombinants/exp. # double recombinants)

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