Chapter 5, Section 3 Meiosis

Meiosis: The process by which chromosome pairs separate and are distributed to two different cells The resulting sex cells have only half as many chromosomes as the other cells in the organism Sometimes a mistake occurs when a gene of a chromosome is made. This is called a mutation. As a result, the organism’s trait, or phenotype, may be different from it normally would have been 2.discoveryeducation.com//downloaddirector/downloadFile.aspx?thefile= v2.1\HeadRush%5FNitro\HeadRush_Nitro_E_256k.wmv&realname=Startli ng_Goats

Before meiosis: Meiosis 1: Every chromosome in the parent cell is copied (prophase) The chromosome pairs line up in the center of the cell (metaphase 1) The pairs separate and move to the opposite ends of the cell (anaphase 1) Two cells form, each with half the number of chromosomes (telophase 1)

Meiosis 2: The chromosomes with their two chromatids move to the center of the cell (metaphase 2) The centromeres split & the chromatids separate (anaphase 2) Single chromosomes move to opposite ends of the cell (telophase 2) At the end of meiosis, 4 sex cells (sperms and eggs) are produced, each with ½ of the chromosomes from the parent cell Why do you think that each sex cell is left with ½ the chromosomes? (meiosis video)

QuickWrite: Compare and contrast the processes of mitosis and meiosis. Use a venn diagram if necessary. end