2. Sturtevant studied flies with mutations in the vermilion gene (abbreviated ,

Question

2. Sturtevant studied flies with mutations in the vermilion gene (abbreviated , recessive phenotype is vermilion-colored eyes) and in crossveinless (abbreviated a, recessive phenotype is a lack of crossveins in the wing). These genes are linked. He crossed crossveinless flies genotype a a with rermilion flies (genotype a* / ). Note that these genotypes could also be represented as ar +/ar + and+,or as a/a +/+ and +/+ v/v, where the slash separates the two chromosomes. Make sure you're comfortable with the notion that these are all representations of the same two-locus genotype, where each chromosome has one allele of the vermilion gene and one allele of the crossveinless gene. It's usually helpful to draw out the chromosomes.) a. What is the genotype of the F, flies? b. What is the phenotype of the F, flies?

Explanation / Answer

Answer:

2).

a). F1 gentoype = cv v+ / cv+ v

b). F1 phenotype = wild-type

Explanation:

cv v+ / cv v+ ( crossveinless wings) X cv+ v / cv+ v (vermilion eyes)—Parents

cv v+ / cv+ v (wild-type)--------------------------------------------------------F1 offspring

c).

Recombination frequency = (total number of recombinants / Total progeny)100

= (169+178 / 2180)100

= 15.92%

Recombination frequency between cv & v = 15.92%

d).

Recombination frequency between ct & cv = (59+54/1800)100

= 6.28%

e).

One map:

cv-------------ct---------v

Another map:

ct---------cv-------v

f):

Recombination frequency between v & ct = (98+90 / 2000)100

= 9.4%

The following map is the most consistent:

cv---------6.28---------ct------9.4mu-----------v

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