Chromosomes are the microscopically tiny, twisted threads inside every cell that carry your body’s life instructions in chemical form.
There are 46 chromosomes in each of your body cells, divided into 23 pairs.
One of each chromosome pair came from your mother and the other from your father.
In a girl’s 23 chromosome pairs, each half exactly matches the other (the set from the mother is equivalent to the set from the father).
Boys have 22 matching chromosome pairs, but the 23rd pair is made up of two odd chromosomes.
The 23rd chromosome pair decides what sex you are, and the sex chromosomes are called X and Y.
Girls have two X chromosomes, but boys have an X and a Y chromosome.
In every matching pair, both chromosomes give your body life instructions for the same thing.
The chemical instructions on each chromosome come in thousands of different units called genes.
Genes for the same feature appear in the same locus (place) on each matching pair of chromosomes in every human body cell. Scientists one day hope to find out how the entire pattern, called the genome, works.