We humans have forty-six chromosomes in the cells of the body and they are located in the nucleus of the cell. They consist of double chains of DNA containing the person’s genetic material. Each chain contains twenty-three chromosome pairs, half of which come from the mother and half from the father.
One of the chromosomes is unique and determines our sex, it consists of either two Xs or an X and a Y. Women are given XX chromosomes and men are born with XY. Because the Y chromosome is smaller than the X chromosome, the male has fewer functional genes. In the Y chromosome, a chain of events begins that leads to an increased production of testosterone and the birth of a male fetus.
The other twenty-two of the chromosome pair are similar. They provide information with your characteristics such as eye and hair colour.
How many chromosomes does a person with Down syndrome have?
Normally, we are born with two pairs of chromosomes, but those born with Down syndrome have three. This development occurs in chromosome number 21 and is called trisomy-21.
