Virgin wildtype female insects were mated with brown-eyed, vestigial-winged, fou
ID: 177334 • Letter: V
Question
Virgin wildtype female insects were mated with brown-eyed, vestigial-winged, four jointed leg males. F1 progeny were all wildtype. Virgin F1 females were mated with brown-eyed, vestifial-winged four jointed leg males in a 3 point testcross. The following testcross progeny were obtained:
18 wildtype
20 brown-eyed, vestigial-winged, four jointed leg
6 vestigial-winged, four jointed leg
5 brown-eyed
4 brown-eyed, four jointed leg
4 vestigial-winged
1 brown eyed, vestigial-winged
0 four jointed leg
a) What is the dominant form of each trait?
b) What are the genotypes of the parents and the F1 progeny?
c) Before you obtained the testcross data above, what would you have predicted? What is your key assumption behind your prediction?
d) What are the double recombiant phenotypic classes?
e) What are the order of the genes?
f) What are the map distances between the genes?
Explanation / Answer
Answer:
a). Wildtype forms are dominat forms of each trait
b).
brown-eyed= b; wild eye=b+
vestigial-wings= v; wildtype wings=v+
Four jointed leg= f ; wild type= f+
The genotype of F1 progeny is b+b f+f v+v.
c) The genes of three traits are linked so that the test cross ratio is deviated from mendel's law.
d). Always double recombinants are very low, so that the double recombinants are brown eyed, vestigial-winged
and four jointed leg
b----f+ -----v & b+-----f-------v+
e). b-------f--------v
f)
The distance between b & f =20.7 m.u.
The distance between f & v =15.6 m.u.
The distance between b & v =32.8 m.u.
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