help parts a b and c! 4. Black body (b/b), curved wing(c/c). known to be on chro

Question

help parts a b and c! 4. Black body (b/b), curved wing(c/c). known to be on chromosome all 3 genes was crossed to a black bodi curved wing(cle), and purple eye color (pr/pr) are recessive traits Drosophila. A testcross of a heterozygous female for 2 in te folowing crossed to a black bodied, curved wing. purple eyed male fly and yielded the followin g progen Phenotype class Number Type Phenotype class Number Type 317 +,pr,c 45 2 23 b, pr,+ 309 b, pr, c Total Progeny 777 a. (4 pt) Give the genotypes of the parents in correct gene order and Drosophila notation. a. (2 pt) Fill in the Type' column indicating which phenotypic classes are parental types (P), region I crossover types (rl), region 2 crossover types (r2), or double crossover types (dco) (9 pts) Calculate the map distances between the genes (give answer in map units): b-pr- c. pr-c= (2 pts) Calculate the value for interference for this cross. d.

Explanation / Answer

(a) Because linked loci tend to stay together, the non-crossover (NCO) or parental phenotypes should be most frequent (and equal in number). In this case:

b pr + (309) i.e. black body purple eye colored, and correct order is pr + b NOTE: pr + b= b + pr

and + + c (317) i.e. corved wings and other trait and correct order is c + + NOTE: c + + =+ + c

(b) Because simultaneous crossovers between the outside and middle loci are unlikely, the double-crossover (DCO) genotypes should be the least frequent. We observe

b pr c (2) & +++ (5)

(c) b---pr

Map distance = No. of recomibinant off spring X 100/ Total off springs

(5+2+ 49+ 45)X100/ 777=12.99 cM

b---c

(5+2+27+23)X100/777=7.335 cM

pr---c = 12.99 cM+ 7.335 cM=20.325 cM

+++ 5 dco + pr c 23 R2 b pr c 49 R1 b pr + 309 P ++c 317 P + pr + 45 R1 b + + 27 R2 b pr c 2 DCO

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