An autosome is a chromosome

Chromosome

A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...

 that is not a sex chromosome, or allosome

Allosome

An allosome is a sex chromosome that differs from an ordinary autosome in form, size, or behavior. The human sex chromosomes are a typical pair of allosomes.The x chromosome is present in the ovum, while x or y chromosomes can be present in sperm.-References:...

; that is to say, there is an equal number of copies of the chromosome in males and females. For example, in human

Human

Humans are the only living species in the Homo genus...

s, there are 22 pairs of autosomes. In addition to autosomes, there are sex chromosomes, to be specific: X

X chromosome

The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals and is common in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system...

 and Y

Y chromosome

The Y chromosome is one of the two sex-determining chromosomes in most mammals, including humans. In mammals, it contains the gene SRY, which triggers testis development if present. The human Y chromosome is composed of about 60 million base pairs...

. So, humans have 23 pairs of chromosomes.

Human chromosomes
Female (XX)	Male (XY)
There are two copies of each autosome (chromosomes 1-22) in both females and males. The sex chromosomes are different: There are two copies of the X-chromosome in females, but males have a single X-chromosome and a Y-chromosome.

See also

• Allosome
  Allosome
  An allosome is a sex chromosome that differs from an ordinary autosome in form, size, or behavior. The human sex chromosomes are a typical pair of allosomes.The x chromosome is present in the ovum, while x or y chromosomes can be present in sperm.-References:...
  
  
• Autosomal dominant
• Autosomal recessive
• Homologous chromosome
  Homologous chromosome
  Homologous chromosomes are chromosome pairs of approximately the same length, centromere position, and staining pattern, with genes for the same characteristics at corresponding loci. One homologous chromosome is inherited from the organism's mother; the other from the organism's father...
  
  
• Sex determination
• Chromosome
  Chromosome
  A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...