Meiosis~ The creation of “ME”

The creation of the sex cells. Happens in germ cells and creates gametes.

A cell division that is NOT a cycle and it includes 2 different divisions.

Uses the same vocabulary as mitosis, but chromosomes line up a bit

differently in Meiosis I, the first division. So structures like tetrads form

from homologous pairs. Also, meiosis has events such as crossing over that

do not occur during mitosis.

Homologous Chromosomes: Same chromosome from each parent

Tetrads: 4 of the same chromosomes (2 from mom and two from dad) or 2

homologous pairs.

Crossing over: Homologous

information (between maternal and paternal)

Meiosis I: INTERPHASE

Homologous chromosomes

pair.

Homologous pairs of chromosomes swapping

information (between maternal and paternal)

NTERPHASE will happen before this first division

Homologous chromosomes pair up (tetrad) and line up randomly with their

pairs of chromosomes swapping genetic

division.

line up randomly with their

Meiosis II: NO INTERPHASE happens…a brief period called interkinesis

happens before the second division. Steps very similar to mitosis steps.

Interphase happens before the first meiotic division, but DOES NOT

happen before the second division; therefore, the chromosome number

gets reduced by ½ (becomes haploid). The time between the first and

second meiotic division is called interkinesis, and it is just a brief period of

time where nothing is happening.

**Diploid (2n) = full set of chromosomes, Haploid (n) = Half set of chromosomes

Meiosis is also referred to as gametogenesis (creation of gametes). In

males, gametogenesis is called spermatogenesis and in females it is called

oogenesis. The process is slightly different between the two processes.

Males produce 4 sperm capable of reproducing offspring. Females produce

1 egg capable of producing offspring and 3 cells that cannot.

Mitosis vs Meiosis: