Ch. 3 Meiosis and Reproduction

Gonads

ovaries and testes, organs that produce sex cells

Sperm

Male sex cell, haploid

Oocyte

a cell in an ovary that may undergo meiotic division to form an ovum.

Gametes

sex cells, sperm or egg

Testes

male gonads

Ovaries

female gonads

Meiosis

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

Diploid

containing two complete sets of chromosomes, one from each parent.

Haploid

having a single set of unpaired chromosomes

Independent assortment

the random distribution of the pairs of genes on different chromosomes to the gametes

Crossing over

the exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring.

Reductive division

where meiosis reduces the number of chromosomes in each cell from 2n to 1n

Equational division

Another name for meiosis II because cells in meiosis II have the same number of chromosomes at the beginning and at the end of the process.

Homologous pairs

A pair of chromosomes of the same type, one from each parent.

Spermatogenesis

production of sperm cells

Spermatogonia

The diploid cells in a testis that can give rise to primary spermatocytes.

Oogenesis

the production, growth, and maturation of an egg, or ovum

Oogonia

an immature female reproductive cell that gives rise to primary oocytes by mitosis

Polar body

haploid cell produced during meiosis in the female of many species; these cells have little more than DNA and eventually disintegrate

Zygote

a diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum.

Embryo

the developing human organism from about 2 weeks after fertilization through the second month

Fetus

In humans, the term for the developing organism between the embryonic stage and birth.

Primary germ layers

ectoderm, mesoderm, endoderm; layers of cells that develop into the body's systems and tissues

Neural tube

an embryonic structure that gives rise to the central nervous system

Teratogens

agents, such as chemicals and viruses, that can reach the embryo or fetus during prenatal development and cause harm