What Is the Role of the Y Chromosome in Sex Determination in Humans?

The Y chromosome determines the sex of an embryo at conception.
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Parents donate a set of chromosomes to their offspring, 23 pairs from each for a total of 46. Each of these chromosomes contains the genetic information that determines everything from the baby's eye and hair color to the baby's sex. Gender is determined by the sex chromosomes. If the Y chromosome is present, the baby will be a boy.

Sex Chromosomes

Out of the 46 chromosomes humans have, only two are responsible for determining the sex of an individual. They are the X and the Y chromosomes. Females carry only the X chromosome, while males carry both X and Y. The X and Y chromosomes carry different genes, and the Y chromosome contains the genes that code for male attributes.

Parents donate a set of chromosomes to their offspring, 23 pairs from each for a total of 46. Each of these chromosomes contains the genetic information that determines everything from the baby's eye and hair color to the baby's sex. Gender is determined by the sex chromosomes. If the Y chromosome is present, the baby will be a boy.

Sex Determination

All female eggs carry one X chromosome; therefore it is the chromosome carried in the sperm that determines the sex of the embryo at the moment of conception. If the egg is fertilized by a sperm with an X chromosome, the embryo develops into a female with an XX genotype. When the sperm carries a Y chromosome, a male embryo results, with an XY genotype.

Parents donate a set of chromosomes to their offspring, 23 pairs from each for a total of 46. Each of these chromosomes contains the genetic information that determines everything from the baby's eye and hair color to the baby's sex. Gender is determined by the sex chromosomes. If the Y chromosome is present, the baby will be a boy.

Embryo Development

The genetic information within the Y chromosome contains the instructions to develop the embryo into a male; in particular, the chromosome has an area called the sex determining region Y (SRY). Until about week seven of a pregnancy, a male embryo and a female embryo are no different. Around this time, genes trigger the formation of the testes in a male embryo. The newly formed testes begin producing hormones, such as testosterone, that further contribute to the physical characteristics of a male.

Parents donate a set of chromosomes to their offspring, 23 pairs from each for a total of 46. Each of these chromosomes contains the genetic information that determines everything from the baby's eye and hair color to the baby's sex. Gender is determined by the sex chromosomes. If the Y chromosome is present, the baby will be a boy.

Genetic Abnormalities

Abnormalities in the Y chromosome are generally not life-threatening or debilitating. A defect may result in incomplete male development and infertility. Additionally, it's possible for an embryo to receive two or more Y chromosomes. Although researchers are still studying this condition, males with extra Y chromosomes may be larger than average or have learning disabilities.

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