1. In Drosophila, the recessive mutations cinnabar (cn, bright red eyes) and vestigial (vg, malformed wings) are linked on the second chromosome. Homozygous parents were crossed to produce F1 progeny. These F1 flies were then testcrossed with cinnabar, vestigial flies to produce the following F2 progeny:
red eyes, normal wings
464 red eyes, vestigial
cinnabar eyes, normal wings 37 cinnabar eyes, vestigial wings 454
Use the data presented above to perform the following tasks:
a. Diagram the chromosomes of the P1, F1, and testcross flies and the crosses done.
b. Diagram how the crossover gametes are produced.
c. Determine whether the traits were in coupling or repulsion in the P1 individuals.
d. Determine the total number of F2 progeny, crossover progeny, and the recombination frequency between cn and vg.
e. Construct a genetic map showing the distance between these two loci.
2. The symbols b, h, and m represent three recessive alleles of genes linked on one of the autosomes of Drosophila. F1 females heterozygous for the three loci were crossed with homozygous recessive males. The following progeny were produced from this cross:
|b m+ h+ 235||b m h+ 90|
|b m h 130||b m+ h 35|
|b+ m h 245||b+ m+ h 80|
|b+ m+ h+ 140||b+ m h+ 45|
Use the data presented above to perform the same tasks (a-e) as you performed for problem #1 AFTER you obtain the order of the genes. In addition, do the following:
f. Calculate the coefficient of coincidence and the interference
g. What percent of the expected double crossovers are actually observed? Why arenít the rest observed?