Loss of heterozygosity is associated with –
**Core Concept**
Loss of heterozygosity (LOH) refers to the loss of one allele of a gene, resulting in the individual being left with only one copy of the gene. This can occur due to various genetic mechanisms, including chromosomal deletion, mutation, or gene silencing. LOH is a key concept in the field of cancer genetics, as it can lead to the inactivation of tumor suppressor genes.
**Why the Correct Answer is Right**
LOH is a critical mechanism underlying tumorigenesis. When a tumor suppressor gene is inactivated due to LOH, the remaining allele may be mutated or silenced, leading to loss of its normal function. This can result in uncontrolled cell growth and tumor formation. In many cancers, LOH is detected at specific chromosomal regions, including the p53 gene locus on chromosome 17p13.1. The p53 gene is a well-known tumor suppressor gene that plays a crucial role in regulating cell cycle and apoptosis.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as LOH is not directly associated with gene duplication, which is a different genetic mechanism that can lead to increased gene expression.
**Option B:** This option is incorrect as LOH is not directly associated with chromosomal translocations, which involve the exchange of genetic material between chromosomes.
**Option C:** This option is incorrect as LOH is not directly associated with gene amplification, which involves the increased copy number of a particular gene.
**Clinical Pearl / High-Yield Fact**
A key clinical correlation is that LOH is a common feature of many types of cancer, including breast, colon, and lung cancer. Understanding LOH is essential for developing targeted cancer therapies that restore normal gene function.
**Correct Answer: D. Tumor suppressor gene inactivation**