A chromosome is one of the threadlike "packages" of genes and
other DNA in the nucleus of a cell.
Different kinds of organisms have different numbers of chromosomes.
Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes and
two sex chromosomes. Each parent contributes one chromosome
to each pair, so children get half of their chromosomes
from their mothers and half from their fathers.
Sources: image from the National Human Genome Research Institute (NHGRI) Genetic Illustrations;
definition from the National Human Genome Research Institute (NHGRI)
Glossary of Genetic Terms