lecture nine
DESCRIPTION
MeiosisTRANSCRIPT
Meiosis and Gene Linkage
PMAT
Chromosome Number
Diploid
Homologous
Haploid
Phases of Meiosis
Meiosis
By the end of meiosis II, the diploid cell that entered meiosis has become four haploid cells
What Happens When It Goes Wrong?
Meiosis I: Prophase
Tetrad
O Crossing Over
Meiosis I: Metaphase
Spindle fibers attach to the chromosomes
Meiosis I: Anaphase
The fibers pull the homologous chromosomes toward opposite ends of the cell
Meiosis I: Telophase and Cytokinesis
Nuclear membranes form. The cell separates into two cells
These two cells enter Meiosis II
Meiosis II: Prophase
Unlike the first division, neither cell goes through a round of chromosome replication before entering meiosis II
Each of the cell’s chromosomes has 2 chromatids
Meiosis II: Metaphase
Chromosomes line up in the center of each cell
Meiosis II: Anaphase
The paired chromatids separate and move toward opposite ends of the cell
Meiosis II: Telophase and Cytokinesis
Each cell separates into two cells - meaning four haploid cells all together
Gamete Formation
In male animals, meiosis produces four haploid sperm cells
However, the cell divisions at the end of meiosis are uneven in females, so that only a single cell receives most of the cytoplasm
Mitosis vs. Meiosis
Gene Linkage
It is the chromosomes that assort independently, not the individual genes
Mendel did not discover gene linkage (Morgan did)
Gene Maps