Homozygosity

Homozygosity for mutations in the Bloom syndrome
gene (BLM) results in an increased rate of
somatic mutations, a manifestation of genomic
instability. The BLM gene on chromosome 15 at
q16.1 encodes a member of the RecQ family of
DNA helicases. The 1417-amino-acid protein
shows homology to the yeast SGS1 gene product
(slow growth suppressor) and the human WRN
gene product (Werner syndrome, McKusick
277700). Allozygous nonsense mutations (two
different mutations in the two alleles of the
same gene) are frequent in the BLM gene. A
characteristic homozygous 6 bp deletion/7 bp
insertion at nucleotide 2281 occurs in Ashkenazi
Jewish