Autosome

Homologous

(of organs) similar in position, structure, and evolutionary origin but not necessarily in function.

Sex chromosome

a chromosome involved with determining the sex of an organism, typically one of two kinds.

Spore

a minute, typically one-celled, reproductive unit capable of giving rise to a new individual without sexual fusion, characteristic of lower plants, fungi, and protozoans.

Chromosome

a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

Egg

an oval or round object laid by a female bird, reptile, fish, or invertebrate, usually containing a developing embryo. The eggs of birds are enclosed in a chalky shell, while those of reptiles are in a leathery membrane.

Autosome

any chromosome that is not a sex chromosome.

Polar body

each of the small cells that bud off from an oocyte at the two meiotic divisions and do not develop into ova.

Genetic variation

in alleles of genes, occurs both within and among populations. Genetic variation is important because it provides the genetic material for natural selection

Sperm

the mature motile male sex cell of an animal, by which the ovum is fertilized, typically having a compact head and one or more long flagella for swimming.