====== 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 |