Understanding Recombination Frequencies: Distance Between Genes Explained

[sonyab523]

Confused on 2 questions here


If a recombination frequency between two genes is 1.5%, what is the distance between the genes in map units on the linkage map?

a. Impossible to determine, because the interference is not known.
b. 1.5
c. 3
d. 0.75

Recombination frequencies

a. arise from completely random genetic exchange.
b. are the same for all genes.
c. decrease with distance.
d. are the same for cis and trans heterozygotes.


My answers (one or both are wrong but I can't tell because they questions are grouped in pairs)

b. Each % frequency of recombination equals one map unit between the genes. So 1.5% recombination frequency = 1.5 map units apart will result in 1.5% recombination

a. It can't be (b), because genes are all distances apart; it can't be (c), because frequencies increase with increasing distance; it can't be (d), because the distance between genes is the same whether the alleles are cis or trans loci. So I thought it was a.

 

[member38644]

Impossible to determine, because the interference is not known.

It is correct to say that the distance between the genes cannot be determined without knowing the interference, but that is not the best answer choice for this question. The correct answer is (c) 3. This is because each % frequency of recombination is equivalent to one map unit, so a recombination frequency of 1.5% means that the genes are 1.5 map units apart on the linkage map.

For the second question, the correct answer is (a) arise from completely random genetic exchange. This is because recombination frequencies are affected by the physical distance between genes, as well as the likelihood of genetic exchange between them. This exchange is influenced by random events, such as the formation of crossover events during meiosis. Therefore, recombination frequencies are not the same for all genes and do not decrease with distance. Additionally, they can vary between cis and trans heterozygotes due to the orientation of the genes on the chromosome.