Interference occurs when a crossover causes the termination of the meiosis event

Question

Interference occurs when a crossover causes the termination of the meiosis event in which the crossover is occurring. one crossover inhibits another. two genes are assorting independently. the number recombinant progeny classes in the testcross of a heterozygote exceeds the number of non recombinant progeny, two genes are far apart on a genetic map. Two linked genes. (A) and (B), are separated by 18 cM. A man with genotype Aa Bb marries a woman who is aa bb. The man's father was AA BB. What is the probability that their first child will be Aa Bb? 25% 82% 9% 41% 18% Define Mendel's Principle of Segregation and the Principle of Independent Assortment. How are they similar and how do they differ?

Explanation / Answer

Whenever one crossing over reduces the rate or inhibits the occurrence of another crossing over in the adjacent region, it is termed as interference.

Mathematically interference is calculated first by calculating the coefficient of coincidence (coc), i.e. by following formula:

Interference=1-coc = observed frequency or number of double recombinant/expected frequency or number of double recombinant

In some regions of chromosomes double recombinants are never observed, hence in these cases coefficient of coincidence becomes zero and interference becomes one, which signifies complete interference.

Normally the magnitude of interference ranges between zero to one,but in exceptional cases it's value can even become negative.

Hence in the first MCQ the correct option is (b)

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