1. Meiosis and Sexual Reproduction
No More Clones!
Isn’t Love Grand?

2. Objectives Understand the meaning of “SEX”
Understand the process of meiosis
Understand the need to undergo meiosis as sexual organisms – to produce change or variation

3. Need For Sex = Need for Change
Sex: results in the new genetic combinations.
Babies look different than parents
New babies = new gene combinations
Meiosis is key to enhancing this variation

4. Sex Terms to Know Diploid: having 2 sets of each chromosome type
You are a Diploid or 2N critter!
Haploid: having 1 set of chromosome type
Egg / Sperm are Haploid
Homologous chromosomes:
Daddy chromosome and Mummy chromosome
Each is a copy. You send either mummy or daddy chromosome into your sex cell (egg or sperm)

6. How they Match Up: Mitosis Meiosis produces 2 daughter cells
daughters are clones of the parent
daughter cells are diploid
growth, replacement, repair
Meiosis
produces up to 4 daughter cells
daughters are distinct from parents
daughter cells are haploid
generation of gametes (sex cells): egg & sperm

7. Meiosis (the process)
Meiosis: nuclear division with a reduction in chromosome number by half
Goal: make 4 sex cells
Process:
Double all DNA
Chromosomes doubled
First Division
2N  1N
Second Division
1N 1N

8. Meiosis Overview Essentially, Double, then Divide Twice then Package 1N (set) of Chromosomes into Egg or Sperm Cell

9. Genetic Variation due to Eggs and Sperm Happening to Meet and Fall in Love 
Variation in the DNA of a zygote
Random fertilization: million possible combinations of sperm and egg = 70,368,744,000,000 possible combinations

10. Variation #2 -- Choosing Mommy or Daddy Chromosome for Egg or Sperm Cell

11. Variation #3 Cross Over -- Mummy and Daddy Chromosomes Hold Hands and Swap Genes
New chromosomes end up in the egg or sperm cells
(4,951,760,200,000,000,000,000,000,000
different zygotes with a single crossover)