Question

Describe how homologous recombination can change DNA sequences by gene conversion vs. how it can cause deletions/insertions.

Answer 1

Homologous recombination is the basic process which is responsible for the crossing over event between chromosomes that occur during meiosis.In this process the nucleotide sequences are exchanged between two similar or identical molecules of DNA ,which results in new combinations of DNA and cause genetic variation.

Gene conversion occur in association with homologous recombination.Gene conversion is a unidirectional transfer of genetic information between two highly homologous genes.

In Gene conversion process DNA genetic information is transferred from a donor sequence (DNA sequence that remains unchanged) to another acceptor sequence (DNA helix whose sequence is altered).Which forms a heteroduplex joint (the two paired strands are not identical in sequence ,which contain some mismatched base pairs ).If this mismatched sequence is removed through DNA repair it can result in an extra copy of the DNA sequence on the opposite strand .This can alter the sequences of one of the chromosomes.

Homologous recombination can cause deletions and insertions.The probability of forming a deletion or insertion depends on the length of DNA homology which is present between the direct repeats.Homologous recombination can cause deletions or insertion in longer regions.

Recombination between the direct repeats results in deletion of intervening genes.

Recombination can result in insertion by duplicating the material between a pair of direct repeats.