1. Meiosis
Chapter 10.1 and 11.3

2. Sexual Reproduction
Sexual reproduction creates genetic variability. That is why we all look different and you look different from your siblings!

3. Define the following words…
Meiosis:
Sexual reproduction-production of gametes
Gamete:
Sex Cells (egg = females & sperm = males)
contain half the number of chromosomes (23)
Somatic Cells:
Body Cells
Contain 46 chromsomes

4. Haploid:
Half the chromosome number (n)
1 of each pair of chromosomes (23)
Gametes are haploid
Diploid:
2 of each type of chromosome (2n)
Somatic cells are diploid
Fertilization:
Sperm enters egg
Zygote:
Fertilized egg (diploid)

5. How many chromosomes do we have in our cells?
Human body cells have 46 chromosomes
Each parent contributes 23 chromosomes
Homologous chromosomes - a pair of chromosomes that have the same genes

6. Homologous Chromosomes
Carry the same genes that control the same inherited traits
Alleles are the variations of one gene
Ex: eye colors can brown, blue, green, hazel, etc….
You inherit one chromosome from each parent!

7. DNA Replication any cell divides, All DNA must be replicated
Unduplicated homologous chromosomes
Duplicated homologous chromosomes

8. Meiosis The sexual life cycle in animals involves meiosis
Meiosis produces gametes (23 chromosomes).
When gametes combine in fertilization, that creates a zygote.
A zygote has 46 chromosomes

10. Meiosis 2 Divisions Meiosis I - separation of homologous chromosomes
Meiosis II - separation of sister chromatids

11. DO NOW
Label the following structures:

12. Do Now
What are ways that increase genetic diversity during meiosis?

13. Meiosis 1
Crossing over occurs
Homologous chromosomes separate, randomly!
46 Duplicated
23 duplicated
Crossing over = the exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring.

14. Crossing over
The same genes “switch”, which allows for unique gametes to form, different from the exact chromosomes given from the mother and father.
Occurs during Meiosis 1, Prophase 1

16. Each gamete has a unique combination of genes!
Meiosis 2
Sister chromatids separate into 4 different gametes, randomly.
23 duplicated
Each gamete has a unique combination of genes!
23 unduplicated chromosomes in each gamete

18. What creates genetic variability?
Crossing over - switching of genes during meiosis 1 creates a unique combination of genes
Independent Assortment - chromosomes separate into gametes randomly during meiosis 1 and meiosis 2
Random Fertilization - random sperm and egg combine to make a unique gamete •

19. Meiosis 1 & 2 - Oogenesis (Eggs) and Spermatogenesis (Sperm)