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Question: Answered & Verified by Expert
An individual homozygous for gene a and b is crossed with wild type and F1 was back crossed with the double recessive. The appearance of the offsprings is as follows

++ 39

ab 31

a+ 17

+b 13

Find out the distance between genes a and b.
BiologyPrinciples of Inheritance and VariationNEET
Options:
  • A 31
  • B 30
  • C 42.8
  • D 3
Solution:
2273 Upvotes Verified Answer
The correct answer is: 30

 

(++) = 39; (ab) = 31; (a+) = 17;(b+) = 13. 
Total number of progeny = 39 + 31 + 17 + 13 = 100. 
No. of recombinants = (a+) + (b+) = 13 + 17 = 30.

Distance between a and b = No. of RecombinantsTotal no. of progeny x 100 =30100 x 100 = 30 cM

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