Topic 3B.3 Sexual Reproduction and Meiosis

diploid (2n)

a cell with a nucleus containing two full sets of chromosomes

haploid (n)

a cell with a nucleus containing one complete set of chromosomes

zygote

the cell formed when two haploid gametes fuse at fertilisation

fertilisation

the fusing of the haploid nuclei from two gametes to form a diploid zygote in sexual reproduction

polyploidy

a cell or an organism with more than two sets of chromosomes

gonads

the sex organs in animals

ovaries

the female sex organs in both animals and plants; they produce the female gametes called ovules in plants and ova in animals

anthers

male sex organs in plants that produce the male gametes contained in the pollen

ovules

the haploid female gametes in plants

pollen

the spore which contains the haploid male gametes of plants

testes

the male sex organs in animals that produce the male gametes - sperm

spermatozoa (sperm)

the haploid male gametes in animals

ova (singular = ovum)

the haploid female gametes in animals

microspores

the result of meiosis in plants that develop into the spore (pollen) containing the male gametes

megaspores

the result of meiosis in plants that develop into female gametes, ovules

homologous pairs

matching pairs of chromosomes in an individual which both carry the same genes, although they may have different alleles

crossing over (recombination)

the process by which large multi-enzyme complexes cut and re-join parts of the maternal and paternal chromatids at the end of prophase I, introducing genetic variation

chiasmata

the points where the chromatids break during recombination

mutation

a permanent change in the DNA of an organism

independent assortment (random assortment)

the process by which the chromosomes derived from the male and female parent are distributed into the gametes at random