3 16 crossing over

Launch

Write the definition of a gene and an allele.

What are the 8 stages of meiosis?

Cell Division

In cell division, new cells are made from an old cell.

During cell division, these chromosomes are copied and one set of chromosomes are given to each new cell.

Meiosis

8 stages:Prophase IMetaphase IAnaphase ITelophase IProphase IIMetaphase IIAnaphase IITelophase II

Homologous Chromosomes

Homologous Chromosomes are chromosomes that contain the same genes, but not necessarily the same alleles

B b

A A

c c

d D

Crossing Over

Crossing over is a process in which different parts of homologous chromosomes switch places

Crossing over leads to increased genetic recombination

This occurs during Prophase I

II. Cell Division-Meiosis

-Crossing over and the exchange of genes in meiosis is a major source of variation among organisms. In meiosis, you end up with 4 daughter cells that can be combined with another sex cell to make a new organism.

MEIOSIS I

MEIOSIS II

Possible gametes Possible gametes

Chromosome A Chromosome B Chromosome a Chromosome b

http://www.youtube.com/watch?v=pdJUvagZjYA&feature=related