Question

34. 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 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?

Answer 1

34. In general autosomal recessive disease will get expressed when the both the recessive alleles are in homozygous condition.

As per the law of inheritance, the dominant gene will get expressed even when it is in heterozygous condition but, this is not true in the case of haplo insufficiency. At this condition the dominant allele will have an insufficiency to show the phenotype, that means it fails to get expressed. Therefore, the disease will come even if there is any single recessive allele (heterozygous) present inspiteof dominant allele.

Young woman's mother has Blooms syndrome but, father does not have. If she is heterozygous for this disease, then there will be a chance for the development of this disease.