Biology Forums - Study Force

Bloom Syndrome
Bloom syndrome is a rare genetic disorder. It is characterized by short stature and a long narrow face with prominent nose and ears. There is also increased sensitivity to light. People who have the disorder often develop rashes on their face, forearms, and hands when they have been exposed to the sun. In addition, these people often suffer from chronic obstructive pulmonary disorder (COPD) and have a higher chance of developing cancer.bloom syndrome


The cause of this genetic disorder is a mutation in the BLM gene located on chromosome 15. The immediate effect of this mutation is that there is a defect in the functioning of the DNA helicase enzyme. The location of this gene on the chromosome is indicated by the yellow arrow.


1. What would be the effect of this mutation on DNA replication? What stage of the cell cycle would be most affected?

2. Note the location of the genes in the diagram of chromosome 15 in question 3.

Is there a higher chance for a crossover between the BLM gene (yellow arrow) and q21.1 (blue arrow) or between the BLM gene and q12 (red arrow). Explain

Helicase unwinds the DNA during DNA replication. It allows the double-stranded DNA into single strands allowing each strand to be copied. Interphase would be impacted because that's when the DNA is replicated prior to mitosis.


There's a higher chance of crossing-over between (BLM gene (yellow arrow) and q21.1 (blue arrow)) because they're closer to the end of the chromosome.