In a three-point testcross, it was found that the genetic map for three linked genes was:...

In a three-point testcross, it was found that the genetic map for three linked genes was: A-----30 m.u.------B------20 m.u----C.

A genetic cross was performed and it the outcome was, that of 1000 progeny, 1 double recombinant was observed. How does this compare to what we would have expected? Interpret and explain this genetic phenomenon? (5 marks)?

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Expert Solution

Answer:

Map distance represents the Frequency of recombination. 1 map unit is equal to 1% recombination Frequency.
The recombination Frequency between gene A and B is 30% , between B and C is 20%.
Recombinant between A and B = 1000 × 30% = 300
Recombinant between B and C = 1000 × 20% = 200
So the expected rate of double recombinant = (300/1000) × (200/1000) = 0.06 or 60 per 1000.
Observed double recombinant = 1
Coefficient of coincidence = 1÷60= 0.016
So, interference = 1 - 0.016 = .984
Interference interpret that crossover in one region of the chromosomes affect the occurrence of crossover at another region.
If the value of interference is "0" then no interference is occurring. If the value is 1 that means complete interference. If the value is in between 0 to 1 that means interference is occurring but not complete.

So, here interference is occurring.

Please Rate My Answer...........Thank...........u...

gladiator answered 2 years ago

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