Sex cell mutations, also known as germline mutations, incorporate altered DNA into all the cells of the body in the offspring that inherits the mutated gene.

Here's why:

* Sex cells (sperm and egg) carry the genetic blueprint for the offspring.

* Fertilization combines the genetic material from both parents, creating a unique combination of genes in the fertilized egg.

* The fertilized egg then divides and develops into all the cells of the body (embryo, fetus, and eventually the adult).

* Every cell in the body will carry the altered DNA from the mutated sex cell, leading to potential changes in the offspring's traits, health, and development.

In contrast, mutations in somatic cells (body cells) are not passed on to offspring. These mutations can only affect the individual in whom they occur.