خدمات / MATERNAL TESTS

Chromosomes are structures within cells that contain a person's genes. A gene is a segment of DNA and contains the code for a specific protein that functions in one or more types of cells in the body (see Genes and Chromosomes for a discussion about genetics).

Every normal human cell, except for sperm and egg cells, has 23 pairs of chromosomes for a total of 46 chromosomes. Sperm and egg cells have only one of each pair of chromosomes for a total of 23. Each chromosome contains hundreds to thousands of genes.

The sex chromosomes are one of the 23 pairs of chromosomes. Normal people have 2 sex chromosomes, and each is either an X or a Y chromosome. Normal females have two X chromosomes (XX), and normal males have one X and one Y chromosome (XY).