How many chromosomes does a human have?

How many chromosomes does a human have? A typical human body cell has 46 chromosomes.

Those 46 chromosomes are arranged as 23 pairs: 22 pairs of autosomes and one pair of sex chromosomes. A person usually inherits one chromosome in each pair from each biological parent. Together, the chromosomes package the nuclear DNA that carries genetic instructions.

The number changes during reproduction. Human egg and sperm cells are haploid, containing 23 chromosomes rather than 46. When they fuse at fertilization, the resulting embryo receives a diploid set of 46. Mature red blood cells are another exception because they lose their nucleus and therefore contain no chromosomes.

The number 46 describes the usual human karyotype, not every individual cell or every person. Some chromosomal conditions involve an extra or missing chromosome; for example, most cases of Down syndrome involve three copies of chromosome 21. Chromosome number also does not measure biological complexity: species with different chromosome counts may have genomes of comparable size.