The three genes for coat color, nose length, and tail length are linked together

Question

The three genes for coat color, nose length, and tail length are linked together on the same chromosome. A black female mouse with a short nose and long tail mates with an albino male mouse with a long nose and short tail. All the resulting F1 progeny are black with short noses and long tails. A female from the F1 generation is testcrossed with a true-breeding albino male mouse with a long nose and a short tail. The observed progeny from this mating are as follows: What is the recombination frequency between the genes for tail length and nose length? Numeric Response

Explanation / Answer

Parental characters = (Maximum individuals progeny) = 180 & 195; Double Cross overs = (Minimum individuals progeny) = 10 & 15; Single Cross Overs nose length: Black-Long nose - Short tail: 65 & Albino-short nose-long tail = 50;

Single cross overs for tail length: Black-long nose-long tail = 75 & Albino-short nose - short tail = 85

Then Recobination of genes between Tail length & skin color = Single crossovers + Double cross overs / Total progeny = (75+85) + (10+15) / 675

= 160 + 25 / 675

= 185/675

= 0.27

Then Recobination of genes between Nose length skin color = Single crossovers + Double cross overs / Total progeny = (65+50) + (10+15) / 675

= 115 + 25 / 675

= 140/675

= 0.20

Noselength--------------------0.20-----------Skin color-----------------------------------------------------------0.27--------------------Tail length

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