Biology Module 9: Meiosis

gamete

A haploid reproductive cell. Upon fertilization, its nucleus fuses with that of another gamete of the opposite sex.

zygote

The diploid (2n) cell resulting from the fusion of male and female gametes (fertilization).

Fertilization

The union of male and female games to form a zygote

Syngamy

Fertillization. The Union of male and female gametes

Meiosis

A special form of nuclear division that precedes gamete dormation in sexually reproducing eukaryotes. (It results in four haploid daughter cells)

diploid

Having two sets of chromosomes (2n), in contrast to haploid (n).

haploid

Having only one set of chromosomes, in contras to diploid.

Sexual Reproduction

Reproduction that involves the regular alternation between syngamy and meiosis. Its outstanding characteristic is that an individual offspring inherits genes from two parent individuals.

asexual repoduction

Reproducing without forming gametes, (no sex), offspring’ is identcial to parent.

somatic cells

All the diploid body cells of an animal that are not involved in gamete formation.

germ-line cells

During zygote development, cells that are set aside from the somatic cells and that will eventually undergo meiosis to produce gametes.

Crossing over

An essential element of meiosis occuring during prophase when nonsister chromatids echange protiens of DNA strands.

Synapsis

Close pairing of homologous chromosomes, occurs in prophase 1 of meiosis, genes of chromosome thus aligned, a DNA strand of one homologue can pair with coplementary DNA strands of the other.

gene

The basic unit of heredity. A sequence of DNA nucleotides on a chromosome that encodes a polypeptide or RNA molecule and so determines the nature of an individual’s inherited traits.

hormone

Chemical messenger produced in one part of an organism, causing a response elsewhere.