Correct option is B
The correct answer is (b).
A missense mutation leading to increased expression of one allele does not result in haploinsufficiency. Haploinsufficiency occurs when one copy of the gene is either deleted or silenced, and the remaining functional copy is unable to produce enough protein for normal cellular function, typically in tumor suppressor genes. A missense mutation can lead to a defective protein, but it doesn’t usually lead to overexpression of the allele. Overexpression is typically not associated with haploinsufficiency, which involves loss or silencing of one allele, rather than increased expression of one allele.
Incorrect options-
Option (a) Deletion causes loss of one allele and is a common cause of haploinsufficiency.
Option (c) Nonsense mutation leads to loss of function, consistent with haploinsufficiency.
Option (d) Epigenetic silencing is a reversible inactivation mechanism that reduces gene expression, causing haploinsufficiency.
