1. Meiosis and Genetic Variation
Biology 4th & 7th
Hall
©Hall2010

2. Gene Variation
There are 3 mechanisms that contribute to genetic variation in sexual organisms.
Independent Assortment
Crossing-Over
Random Fertilization

3. Independent Assortment
Each gamete receives one chromosome from each of 23 pairs of homologous chromosomes
Which chromosome the gametes receive is up to chance
There is random distribution during meiosis

5. Crossing-Over
DNA exchange that occurs during crossing-over adds even more recombination to independent assortment
Number of genetic combinations that can occur are almost unlimited

6. Random Fertilization Zygote is formed by random joining of 2 gametes
million sperm per ejaculation
Typically one egg, although more than one is possible

7. Importance of Genetic Variation
ESSENTIAL TO EVOLUTION
Generates variation the quickest
Pace of Evolution increases as the level of genetic variation increases
Natural Selection does not always favor genetic or outward change.

8. Chick Variation