What are germ cell mutations?
A germ cell mutation is any detectable and heritable variation in the lineage of germ cells.
The presence of an altered gene within the egg and sperm (germ cell) such that the altered gene can be passed to subsequent generations.
Mutations in these cells are transmitted to offspring, while, on the other hand, those in somatic cells are not.
A germ cell mutation gives rise to a constitutional mutation in the offspring, that is, a mutation that is present in virtually every cell.
An example of a chromosome mutation in a sex cell would be trisomy 21 (aka downs syndrome), where a sex cell has an extra chromosome due to a homologous pair of chromosomes failing to separate during meiosis.