Loss of heterozygosity

Imagine you have a friend named George and he has two different colored markers, one blue and one red, and he shares them with you. This means you both have one blue marker and one red marker. You have one marker of each color and George has one marker of each color.

Now imagine if one day you lose your blue marker and can’t find it anywhere. You only have a red marker left. This is what happens when there is a loss of heterozygosity. Heterozygosity means having two different versions of a gene. Just like how you and George each had two different markers, cells in our bodies have two copies of each gene. When a cell loses one copy of a gene due to a mutation or deletion, it becomes homozygous, meaning it only has one version of the gene.

This can lead to problems because having two versions of a gene allows for backup in case one version doesn’t work properly. With only one version, there is no backup and the cell may not function properly. This can lead to the development of tumors, as cells with a lost copy of a tumor suppressor gene can grow uncontrollably.