Answer:
Early in the development of the embryo, specialized diploid cells, called germ cells , are produced within the gonads (such as the testes and ovaries). Germ cells are capable of mitosis to perpetuate the germ cell line and meiosis to produce haploid gametes.
If the DNA strand is mutated it can cause genetical and physical defects. Just as an extra chromosome can cause Trisomy 21 which cause Down Syndrome.
