Homozygous Loss
Homozygous loss refers to the complete deletion or inactivation of both copies (alleles) of a gene in a diploid organism. This term is commonly used in genetics, molecular biology, and cancer genomics.
What Does It Mean?
Humans typically have two copies of each gene (one from each parent). A homozygous loss means that both copies of a gene are deleted, mutated, or otherwise inactivated, resulting in loss of gene function.
Example
In cancer, homozygous loss of the CDKN2A gene is common and leads to the loss of tumor suppressor function (p16^INK4a^), promoting uncontrolled cell proliferation.
Key Points
| Feature | Explanation |
|---|---|
| Zygosity | Homozygous = both alleles are affected |
| Mechanism | Large deletions, point mutations, LOH + mutation |
| Consequence | Often results in loss of gene function |
| Clinical relevance | Seen in tumor suppressor gene deletions (e.g., TP53, PTEN, RB1) |
| Detected by | Genomic techniques such as FISH, aCGH, NGS, or SNP arrays |