Lesson 2: The Structure of DNA
Women have, normally, two copies of every chromosome except the Y chromosome. Women do not have the Y chromosome. Men have, normally, two copies of every regular (autosomal) chromosome and only one copy each of the X and Y chromosomes. Humans have a total of 46 chromosomes inside nearly all of their cells. There are 22 paired autosomal chromosomes and a pair of sex chromosomes, making 23 pairs of chromosomes. Because the genes are the same on each pair of autosomal chromosomes, we have a backup copy of most of our genes.
Each different kind of chromosome is colored differently in this diagram of the chromosomes found in a woman. The two X chromosomes (pink) are in the lower right corner.