Bloom syndrome (OMIM 210900) is an autosomal recessive disorder caused by mutation of a DNA helicase. Among the principal symptoms of the disease are chromosome instability and a propensity to develop cancer. Explain these symptoms on the basis of the helicase mutation.

Key Concepts

DNA Helicase Function

DNA helicases are essential enzymes that unwind the DNA double helix during replication and repair processes. They separate the two strands of DNA, allowing other proteins to access the genetic information. Mutations in helicase genes can disrupt this unwinding process, leading to errors in DNA replication and repair, which can contribute to genomic instability.

Chromosome Instability

Chromosome instability refers to an increased rate of chromosomal alterations, such as breaks, rearrangements, or aneuploidy. This instability can arise from defective DNA repair mechanisms, often due to mutations in genes like those encoding helicases. In Bloom syndrome, the inability to properly manage DNA replication and repair leads to a higher likelihood of chromosomal abnormalities.

Cancer Propensity

The propensity to develop cancer is often linked to genetic mutations that compromise the integrity of the genome. In Bloom syndrome, the combination of chromosome instability and impaired DNA repair mechanisms increases the risk of mutations accumulating in oncogenes and tumor suppressor genes, ultimately leading to cancer development. This highlights the connection between genetic disorders and cancer susceptibility.