Meiosis 11-28-2017

Cell Cycle Review Interphase includes G1 S phase G2 Mitosis includes Prophase Metaphase Anaphase Telophase The final stage of the cell cycle is Cytokinesis

Meiosis – type of cell division that results in 4 daughter cells each with half the number of chromosomes as the parent cell

Meiosis IPMATPMAT Meiosis includes Interphase Mitosis I Cytokinisis I Prophase I Metaphase I Anaphase I Telophase I Cytokinisis I Mitosis II Prophase II Metaphase II Anaphase II Telophase II A second stage of interphase is missing in meiosis This is important because the DNA replicates during interphase. Meiosis goes through a second division without replicating the DNA, resulting in cells with only half the DNA as the parent cell

Meiosis Meiosis produces 4 haploid cells known as gametes. Each gamete is UNIQUE and will be used for sexual reproduction. Diploid number of chromosomes for a human is 46 (2n = 46) Haploid number of chromosomes for a gamete cell is 23 (n = 23)

Sexual Reproduction Meiosis reduces the chromosome number to one set (n) Fertilization restores the diploid number (2n) when the gametes are combined Ex - sperm cell combines with egg cell In sexual reproduction, two individuals (parents) contribute genes to the offspring. This form of reproduction results in greater genetic variation in the offspring than asexual reproduction.

Male vs. Female Meiosis in males produces 4 sperm cells These sperm cells are haploid cells (n) Meiosis in females produces 4 egg cells These egg cells are haploid cells (n) When the sperm cell combines with the egg cell it results in a diploid zygote (2n)

♂ Male ♂

♀ Female

Genetic Variation Crossing Over: portions of a chromatid on one homologous chromosome are broken and exchanged with corresponding chromatid portions of the other homologous chromosome. This increases genetic variation.

Identical diploid cells Comparing Mitosis and Meiosis Mitosis Meiosis # of chromosomes in G1 46 (2n) # of chromosomes after S 92 # of chromosome divisions 1 division 2 divisions # of chromosomes in final cell 23 (n) # of final cells 2 ♂= 4 sperm cells ♀= 4 egg cells Type of final cell Identical diploid cells Unique haploid cells