Meiosis- gamete formation

Mader Chapter 17.3

Mitosis does not alter the chromosomal makeup of cells

Chromosome number must be reduced when gametes are produced

Meiosis separates homologous chromosomes

There are 2N Possible arrangements of homologues

Humans have 23 pairs of homologous chromosomes N=23There are 223 possible arrangements of homologues = 8,388,608

Four of the eight possible arrangements for a N = 3 organism are shown above. Each Arrangement2 gametes so there are 8 possible gametes!

Crossing over generates even more diversity

Meiosis

Separates homologous chromosomes Chromosome number goes from 2N N Generates a very diverse set of gametes

each of which contains a nearly unique set of maternal and paternal genes

Spermatogenesis

Human ova are ovulated arrested in meiotic prophase II

The human life cycle