Humans have 44 autosomes, which is a total of 22 pairs of autosomes. Autosomes are the chromosomes that determine what proteins are made in the body that are not related to sex. In all, humans have 23 pairs of chromosomes, one pair of which are the sex chromosomes, the X and Y chromosomes.
Not all the autosomes are the same size. The largest autosome is Chromosome 1, which has about 2,800 genes. The second largest autosome is Chromosome 2, which contains about 750 genes.
Usually, one of each set of chromosomes is inherited from each parent. In a condition called trisomy, two chromosomes are inherited from one parent and one is inherited from the other. Trisomy 21, also known as Down Syndrome, results when an individual has three copies of the autosome Chromosome 21.