1. Meiosis
Biology

2. Human Chromosomes Every normal human cell has, 23 pairs of chromosomes
Total chromosomes = 46
22 pairs contain genes that code for normal, human traits
Ex: eye color
Chromosomes # 1-22
1 sex chromosome pair
Chromosomes that determine sex
Females = XX, Males = XY
Chromosome # 23

3. Meiosis is:
A process in the body that makes sperm and egg

4. In Meiosis:
Crossing over occurs
Exchange of information when homologous chromosomes cross each other
Results in an increase of diversity- chromosomes are now mixed

5. Review: Mitosis
End with the same number of chromosomes as the original cell
One cell divides into 2 identical “daughter” cells
Occurs in body cells
Ending cells have pairs of chromosomes
For growth, repair and to replace cells

6. What is meiosis?
End with half the number of chromosomes as the original cell
One cell divides two times into 4 “daughter” cells
Occurs in reproductive cells of an organism
Ending cells do not have pairs of chromosomes
For the production of gametes (gametes are sex cells)

7. What’s a gamete? Scientific name for a sex cell
2 Types of Sex Cells:
In females: Egg
An egg is a cell containing half of a woman’s chromosomes
In males: Sperm
Sperm is a cell containing half of a man’s chromosomes
egg
sperm

8. Where are gametes made?
In Females:
In Males:
Ovaries
Testes

9. Meiosis in females…. meiosis results in the production of one egg cell
Babies are born with all the cells that will become eggs (approximately 150,000)
After puberty, one egg will be made every month until eggs run out (approximately 400 eggs will be released)

10. Menopause
When a woman no longer matures and releases eggs

11. Meiosis in males….
In males, meiosis results in the production of 4 new cells
Babies are born with cells that will become sperm
After puberty, sperm are made every day (approximately 300,000,000 per/day) until death