1. MEIOSIS
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2. Parents can produce many types of offspring
Families will have resemblances, but no two are exactly alike

3. Every cell has a nucleus Every nucleus has chromosomes The number of chromosomes depends on the species Ex.  Humans have 46

4. GENES
are located on chromosomes
genes control the TRAITS of the individual

5. Chromosomes come in matching sets -these are called homologous pairs

6. Cells in your body have two sets (in pairs, 46 total) - they are called DIPLOID  
Sex cells (sperm and eggs) only have one set (no pairs, 23 total)  - they are called HAPLOID

8. FIND THE HOMOLOG!

9. When GAMETES combine, the ZYGOTE (offspring) gets half from mom (23) and half from dad (23)
ZYGOTES are diploid  (46)

10. When sperm and egg meet, their chromosomes must match for the zygote to develop properly.

11. Let's review terms......
1.  Matching sets of chromosomes are called ________ pairs
2.  Egg and sperm combine to make a _______________
3.  Egg and sperm are both known as _______________
4.  A cell that only has half of a set of chromosomes is said to be _______________.
5.  Genes are located on  ___________________

12. The process of creating a gamete (sex cell) is called MEIOSIS
It is similar to mitosis, but  will produce 4 daughter cells that are each haploid.

13. OOGENESIS - makes eggs (ovum)

14. Spermatogenesis - makes sperm

15. PROPHASE I of MEIOSIS - homologous pairs form
-chromosomes trade genes, 
CROSSING -OVER

16. Crossing-over increases the number of possible gene combinations
Why is genetic variability important?

17. Steps of Meiosis

19. Asexual vs. Sexual Reproduction
Asexual Reproduction by mitosis is a careful copying mechanism. Some unicellular organisms, like amoeba, produce asexually.
However, these offspring are always genetically identical to the parent.
Sexual Reproduction by meiosis bring genetic variability of offspring.
The number of possible chromosome combinations is 2n. Therefore, humans have 23 chromosomes, so 223 = 8,388,608 genetic possibilities.

20. THE END
Up Next: Section 5

21. Meiosis My Notes
During meiosis I, each set of replicated chromosomes line up with its homologous pair.
Homologous chromosomes= matched pairs of chromosomes. Similar in size, shape, and carry the same kinds of genes.
These homologous pairs exchange pieces during the crossing over process. This results in genetic variation.
Interkinesis is the resting period before meiosis II begins.

22. Meiosis My Notes During meiosis II, the 2 daughter cells divide again.
This results in 4 gametes, each having half the number of chromosomes of the mother cell.
In human males, all 4 gametes each produce long whip-like tails, now called sperm.
In human females, 1 gamete forms an egg cell. The other 3 gametes, called polar bodies, disintegrate.
Meiosis is vital to maintaining the correct number of chromosomes. If extra or not enough chromosomes are passed on, diseases can result.