Question

Bloom syndrome is an autosomal recessive disease that exhibits haploinsufficiency. A recent survey showed that people heterozygous for mutations at the BLM locus are at increased risk of colon cancer. Suppose that a young woman is referred to a genetic counselor. The young woman's mother has Bloom syndrome but the young woman's father has no family history of Bloom syndrome. The young woman asks whether she is likely to experience any other health problems associated with her family history of Bloom syndrome. What advice would the genetic counselor give her?

A. Based on her family history, she is likely to be homozygous normal at the BLM locus and, therefore, not expected to experience any health problem associated with Bloom syndrome
B. Based on her family history, she will be homozygous for a mutated BLM allele and will have an increased risk of colon cancer
C. Based on her family history, she is heterozygous for a mutated BLM allele but will not have an increased risk of colon cancer because the mutant BLM allele is haploinsufficient
D. Based on her family history, she has only a 50% chance of inheriting a mutated BLM allele and the associated risk of colon cancer Based on her family history, she is heterozygous for a mutated BLM allele and will have an increased risk of colon cancer.

Answer 1

Based on her family history, she has only a 50% chance of inheriting a mutated BLM allele and the associated risk of colon cancer.

Option: (D)

Step-by-step explanation:

• Bloom syndrome is a heredity disorder which causes reduced height and develops skin rashes when exposed to sunlight. This may lead to formation of skin cancer.

• Haploinsufficiency is a condition in which one allele is inactive and the existing allele is not sufficient to produce the required gene product for the normal function.

• BLM is a gene required for the making of a protein called RecQ helicase.

• There is no cure for the bloom syndrome and children with this disease should be given proper nourishment.

• Bloom syndrome occurs due to the 'mutation of the BLM gene' located in the 15th chromosome.