Bloom syndrome is an autosomal recessive disease that exhibits haploinsufficiency. A recent survey showed that people heterozygo
us for mutations at the BLM locus are at increased risk of colon cancer. Suppose you are a genetic counselor. A young woman is referred to you whose mother has Bloom syndrome; 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 you give her?
The correct answer is - she is heterozygous for a mutated BLM allele and will have an increased risk of colon cancer.
Explanation:
Autosomal recessive disease expresses itself in next-generation only if there is both alleles are recessive for the gene. In haploinsufficiency, the dominant allele fails to express itself in the phenotype due to insufficiency. So, if even one allele of the recessive gene present in the haploinsufficiency case, it will affect and express its trait.
She is heterozygous for a blood syndrome, as her mother had but her father has no disease, allele and will have an increased risk of colon cancer.
