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Male sperm cells in humans and other mammals are heterogametic and contain one of two types of sex chromosomes. They contain either an X chromosome or a Y chromosome. Female egg cells however, contain only the X sex chromosome and are therfore homogametic. The sperm cell determines the sex of an individual. If a sperm cell containing an X chromosome fertilizes an egg, the resulting zygote will be XX or female.
mtDNA for Genealogy. 1  Both Males and Females can take this test. 2  Females carry a specific DNA material that is useful in genealogy called the mitochondria, or mtDNA. This is the material that surrounds the chromosomes. 3  The mtDNA is passed from a mother to her children, essentially unchanged.