A fruit fly of genotype A/a. B/b (parent 1) is crossed to another fruit fly of g

Question

A fruit fly of genotype A/a. B/b (parent 1) is crossed to another fruit fly of genotype a/a.b/b (parent 2). The progeny of this cross were: Genotype    Number of individuals A/a. B/b 32 a/a.b/b 33 A/a.b/b 17 a/a. B/b 18 What gametes were produced by parent 1 and in what proportions? Do these proportions demonstrate independent assortment of the two genes? What can be deduced from these proportions? Draw chromosomal diagram(s) to illustrate the arrangement of the genes on the chromosomes in parents 1 and 2. Draw a diagram or diagrams to explain the origin of the two rarest progeny genotypes.

Explanation / Answer

Ans Q10.
a) Parent 1 fruitfly of A/a.B/b genotype had produced gametes of following types:

AB, Ab, aB, ab in non equal proportion i.e. 32:17:18:33

b) The proportion don't demonstrate independent assortment of the two genes as it is not equal i.e. 1:1:1:1 (25% each).

c) Besides unindependent assortment linkage bigger than cross over between the genes can also deduced from these proportions.

d) Chromosomal diagram of Parent 1:
   __A/a__B/b__ the genes are 17+18=35 map unit apart from each other
  
Chromosomal diagram of Parent 2:
   __a/a__b/b__the genes are 17+18=35 map unit apart from each other
e) The two rarerest progeny genotype originates when crossing over occurs between the two genes for example

   __A__ _b__   
/
   __a__/_b__

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