The male chromosome is the Y chromosome, which is one of the two sex chromosomes in humans. Females have two X chromosomes, while males have one X and one Y chromosome
. The Y chromosome is responsible for male sex determination, but it does not singularly define a person's sex. The Y chromosome carries a gene that encodes a testis-determining factor, which organizes the gonad into a testis rather than an ovary
. The Y chromosome is one-third as long as the X chromosome and has just around 100 protein coding genes, which is the fewest genes of any chromosome
. The Y chromosome is frequently used in genealogy because it is only passed down from male parent to male offspring
. Beyond its role in sex determination and fertility, the Y chromosome also contains important genes that are critical for the health and survival of individuals
