A female of genotype produces 100 meiotic tetrads. 68 show no crossover events 2

Question

A female of genotype

produces 100 meiotic tetrads.

68 show no crossover events
20 show a crossover between a and b
10 show a crossover between b and c
2 show a double crossover between a and b and between b and c

Of the 400 gametes produced, how many of each of the eight different genotypes will be produced? (Hint: Recall that there are four chromatids in each tetrad and a single crossover involves only two of the four chromatids. Noninvolved chromatids must be added to the noncrossover classes.)

Label the diagram by dragging the labels to the appropriate targets. Note: not all labels will be used.

abc

+++

a++

+bc

++c

ab+

+b+

a+c

how many are in each of those

Explanation / Answer

Ans.) The number of gametes according to their is given below-

Genotype ----------------- No of gametes

a b c ------------------------ 136 + 20 + 10 + 2 = 168

+ + + 1 --------------------- 36 + 20 + 10 + 2 168

a + + ------------------------ 20

+ b c ------------------------ 20

a b + ------------------------ 10

+ + c ------------------------ 10

a + c ------------------------ 2

+ b + ------------------------ 2

ans.) The map distance between a and b

= (40+4/400) x100

=11 mu

Hence, the map distance between a and b is 11mu.

c.) In the same manner, the map distance between b and c is 6mu.

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