Question

What is the mechanism by which recurrent deletions associated with contiguous gene syndromes occur?

A Restriction enzymes delete sequence at particular sites
B Aberrant recombination occurs between low copy repeats
C Deletions are flanked by fragile sites on the chromosome
D Recombination occurs with a nonhomologous chromosome
E Excision of ancient retroviral elements occurs

Answer 1

Contiguous gene syndromes are often caused by aberrant recombination between low copy repeats in the genome, leading to recurrent deletions of the genes located between these repetitive sequences.

Step-by-step explanation:

The mechanism by which recurrent deletions associated with contiguous gene syndromes occur is most commonly due to aberrant recombination between low copy repeats (LCRs). LCRs are sequences that are present in multiple copies in the genome and can misalign during meiosis, leading to unequal crossing-over. This can result in a deletion of the intervening genes between the LCRs, giving rise to the phenotypes observed in contiguous gene syndromes.

Recurrent deletions are not typically caused by restriction enzymes, fragile sites, recombination with a nonhomologous chromosome, or the excision of ancient retroviral elements. Instead, the high similarity of LCRs can cause them to align improperly during recombination, a process which normally maintains genetic integrity. When misalignment occurs, it can lead to genetic errors such as the deletions seen in these syndromes.