The order of genes on a plant chromosome is A, B, and D, where A and B have a recombination frequency of 0.2, and B and D have a recombination frequency of 0.3. A pure-breeding plant that has the dominant A and B phenotypes with a recessive d phenotype is crossed to a pure-breeding plant that has the recessive a and b phenotypes with the dominant D phenotype. The resulting hybrid is crossed to a plant that has all three recessive phenotypes. Under the assumption that interference in this region is zero, what percentage of each progeny type would result from a single crossover between A and B

Question

Biology

Oprah

16 April, 20:26

The order of genes on a plant chromosome is A, B, and D, where A and B have a recombination frequency of 0.2, and B and D have a recombination frequency of 0.3. A pure-breeding plant that has the dominant A and B phenotypes with a recessive d phenotype is crossed to a pure-breeding plant that has the recessive a and b phenotypes with the dominant D phenotype. The resulting hybrid is crossed to a plant that has all three recessive phenotypes. Under the assumption that interference in this region is zero, what percentage of each progeny type would result from a single crossover between A and B

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Answers (2)

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Lena Robertson · Answer 1

It is given that RF (recombination frequency) between A and B = 0.2

RF between B and D = 0.3

Now, DCO (Double Crossover frequency) can be calculated as 0.2 X 0.3 = 0.06

Interference assumed = 0

We can now calculate for SCO as RF (B and D) - DCO frequency

= 0.3 - 0.06 = 0.24

Since, the result of each recombinant event is two recombinant types, hence,

24/2 = 12% Abd/abd and 12%aBD/abd

Reid Lawrence · Answer 2

Answer: 12% Abd/abd 12%aBD/abd

Explanation: When recombination frequency (RF) between A and B is given as 0.2

Recombination frequency between B and D = 0.3

Where double crossover frequency (DCO) is calculated as 0.2 * 0.3 = 0.06

The interference assumed as = 0

Single crossover (SCO) can be calculated as recombination frequency of (B and D) - Double crossover frequency which is 0.3 - 0.06 = 0.24

Each recombinant event has an overall result of two (2) types

Therefore; 24:2 = 12%

= 12% Abd/abd and 12%aBD/abd