1. MEIOSIS

2. Structure of Chromosome

3. Diploid Vs. Haploid Diploid - two sets of chromosomes
Haploid - one set of chromosomes
Diploid cells (2n or 2 sets of chromosomes) are made into haploid (1n or 1 set chromosomes) during meiosis
Examples of diploid cells: almost all your cells! Most plant & animal cells are diploid (2n)
Examples of haploid cells: gametes, egg & sperm (n)

4. How Many Homologous Chromosomes?
Homologous pairs carry genes controlling the same inherited traits.
Humans have 23 pairs of homologous chromosomes.
a. 22 pairs of autosomes
b. 1 pair of sex chromosomes

5. Sex Chromosomes
XX chromosome - female
XY chromosome - male

6. Homologous Chromosomes
Each organism that is produced via sexual reproduction has 2 copies of autosomes, one comes from each parent
Homologous chromosomes (Homo=same) chromosomes that are the same size & shape; carry genes for the same traits

7. History of Life

8. Review Mitosis

9. Meiosis
Meiosis: the form of cell division where sex cells are produced (gametes).
Purpose: to produce sex cells (gametes) for sexual reproduction
Sex cells (sperm or egg) have half the # of chromosomes as a normal body cell

10. Diploid to Haploid

11. Spermatogenesis & Oogenesis

12. Fertilization n= 23 2n = 46 zygote egg
The fusion of a sperm and egg to form a zygote.
n= 23
egg
sperm
n = 23
2n = 46
zygote

13. Question:
A cell containing 20 chromosomes (diploid) at the beginning of meiosis would, at its completion, produce cells containing how many chromosomes?
ANSWER = 10 chromosomes (haploid)
Animation

14. Comparison
Mitosis
Meiosis