Question

In a given mapping experiment, you expect that incidence of double crossovers is 3.5%, but you only observe 2.5%. This can be explained by ________________.

Answer 1

Observing a lower incidence of double crossovers than expected can be attributed to interference, illustrating the complex interactions that can influence genetic mapping and the calculation of recombination frequency and genetic distance.

Step-by-step explanation:

In a given mapping experiment, the lower than expected incidence of double crossovers could be explained by interference. Interference occurs when the occurrence of one crossover event in a region reduces the likelihood of a second crossover occurring nearby.

If we initially expect a 3.5% incidence of double crossovers but only observe 2.5%, it suggests that interference is occurring. This phenomenon affects the calculation of recombination frequency and could lead to an underestimate of the genetic distance between two loci on a chromosome.

Using large numbers of crosses, as Mendel did, we understand that the further apart two linked genes are on a chromosome, the more likely it is that recombination events will cause nonparental genotypes. However, with interference, even genes that are quite far apart may show less recombination than expected, leading to a lower observed frequency of double crossovers.