Ch 12 - Meiosis & Genetic Diversity

meiosis - process of cell division that is used in gamete formation

• haploid gametes (n) from diploid (2n) parent cells

• haploid egg is fertilized by haploid sperm = zygote has diploid number of chromosomes

• four genetically different haploid gametes

meiosis 1 - first round of cell division; also known as reduction division

• prophase 1: prophase + homologous chromosomes pair up and genetic recombination (crossing over) takes place

• metaphase 1: chromosomes line up in homologous pairs along center of the cell

• anaphase 1: pairs of homologous chromosomes separate and # of chromosomes remains the same

• telophase 1: two new nuclei are formed —> two haploid cells (n)

meiosis 2: second round of cell division

• prophase 2: chromosomes condense and become visible

• metaphase 2: chromosomes line up in along center of each cell

• anaphase 2: sister chromatids move to opposite ends of the cell —> separate chromosomes

• telophase 2: each cell is split into two cells —> four haploid gametic cells

synapsis - homologous chromosomes pair up in this process to form tetrads in prophase I

• exchange genetic information through genetic recombination

• farther genes have higher chance of recombination

linked genes - genes that are close together on the same chromosome tend to be inherited together more often

translocation - genetic change in which a piece of one chromosome breaks off and attaches to another chromosome

nondisjunction - pairs of homologous chromosomes all move to the same side of the cell —> end up in the same gamete

aneuploidy - atypical number of chromosomes