1. Aim: How does meiosis and fertilization increase variation among offspring?

2. What do these pictures show?
VARIATION!!

3. Measure your partner’s ear length
Are every bodies ear length the same?
Why not?
Genetic variation

4. I. Variation between organisms due to:
*Meiosis: which involves…
a. crossing over
b. independent
assortment
c. Fertilization

5. II. Meiosis Review: DNA replicates
Prophase I: synapsis & crossing over
1st Division – 2 cells
2nd Division – 4 haploid cells

6. *Crossing Over:
*SYNAPSIS and genes exchanged

7. III. Genetic Recombination:
*During Crossing Over, genes change their location.
*This change increases genetic variation which leads to offspring with different appearances.

8. IV. Independent Assortment:
*The chromosomes separate randomly into gametes.

9. V. What is the result of independent assortment?
*Different combinations of genes in gametes

10. VI. Fertilization
*During fertilization a mother’s genes (egg) & a father genes (sperm) combine. This combination of genes results in Genetic Recombination.

11. *It all leads to… Trillions of possible combinations
= Variation

12. VII. SUMMARY:
What type of cell division leads to variation?
MEIOSIS
Name three ways meiosis leads to variety.
1. Crossing-over, 2. Independent assortment, and 3. Fertilization.
How does fertilization lead to genetic variation?
Half of the genes come from the mom and half come from dad, resulting in a new combination of traits.