Question

calculate the rate of crossing over

Answer 1

Hello @mohamedsherif !

Answer 2

In the following passages i'll be trng to explain u what crossing over rate is and how to calculate it !

In genetic mapping different genes are linearly arranged according to their % of crossing over or recombination frequency or cross over frequency. Genes have different recombination frequencies depending on how closely linked they are. The genetic distance between genes is measured in map units (mu), where 1 mu is defined as the interval in which a 1% crossing over takes place. It is not a unit of physical distance like nanometers, but an indirect measure of distance on the basis of a probability. The higher this probability, the further the genes are from one another physically. The frequency of recombination is proportional to the distance between genes. The first genetic map ever constructed was based on recombination frequencies from Drosophila crosses involving the X-linked genes w (white eyes), m (miniature wings), and y (yellow body). In each cross, the number of parental progeny was much greater than the number of recombinant progeny. The percentages of recombinants were calculated for each cross. The recombination frequencies were:

w-m – 32.7 % [which means that probability of coming together of w & m genes was 32.7 %]
w-y – 1.0 % [which means that probability of coming together of w & y genes was 1.0 %]
m-y – 33.7 % [which means that probability of coming together of m & y genes was 33.7 %]

Chromosome: y__w___________________m
- 1.0 mu - - 32.7 mu –
Thus y and W are closest together since they have the lowest frequency of recombination. We also know that the m-w distance is shorter than the m-y distance, since m-y has a higher frequency of recombination than does w-m.