Genetic Influences On Behavior Chromosomes and Genes Chromosomes come in pairs. Normally, each cell in the human body has 23 pairs of chromosomes (46 total chromosomes). Half come from the mother; the other half come from the father.
Sex-Linked Genes
Chromosomal Abnormality A chromosomal abnormality occurs when there is a change in the number or structure of chromosomes in a person's cells. These happen when a person has too many or too few chromosomes. For example, instead of the usual 46 chromosomes (23 pairs), a person might have 47 or 45. These occur when a chromosome is missing pieces, has extra pieces, or has pieces rearranged.