 In contrast to a gamete, the diploid somatic cells of an individual contain one copy of the chromosome set from the sperm and one copy of the chromosome set from the egg cell; that is, the cells of the offspring have genes expressing characteristics of both the "father" and the "mother".A gamete's chromosomes are not exact duplicates of either of the sets of chromosomes carried in the diploid chromosomes, and may undergo random mutations resulting in modified DNA and subsequently, new proteins and phenotypes.Humans and most mammals use the XY sex-determination system in which a normal ovum can carry only an X chromosome whereas a sperm may carry either an X or a Y chromosome.