Question

how does recombination affect gamete frequency

Answer 1

Physical crossing over in meosis 1 is an event in which heterozygous homologous chromosomes are rearranged into new combinations. This is also called recombination. Recombination can occur between any two genes on a chromosome, the amount of crossing over is dependent on how close the genes are to each other on the chromosome. If the genes are on the opposite end the cross-over and non crossover events will occur in equal frequency. Genes that are closer to each other undergo few crossing over events, thus the number of non-crossover gamates will be more than crossover gametes. Two types of gametes are possible :

1. Parental gametes : If no recombination occurs.
2. Recombinant gametes : If crossing over occurs.

The allelic composition of both the parental and recombinant gametes is dependent upon whether the original cross involves genes in coupling or repulsion phase. Recombinant gametes are the ones which are found in the lowest frequency.This is the result of the reduced recombination that occurs between the two genes that are located close to each other on the same chromosome. For a coupling phase cross the most prevelant gametes will be those with either two dominant allels or with two recessive allels. For replusion phase cross one dominant and one recessive allele will be the most abundant.