1. Differentiation in somatic cells
The body organs are formed from a variety of these tissues.
During cell division the nucleus of a somatic cell divides by mitosis to maintain the diploid chromosome number.
Diploid cells have 23 pairs of homologous chromosomes.
 What is mitosis and how does it happen again?
Diploid – containing 2 set of chromosomes (1 from each parent) (2n)

2. Bell Work – Put these statements in order to create a flow chart of mitosis in your books
Two new nuclei form
Chromosomes are pulled apart
Chromosomes become visible
Chromosomes line up along the centre of the cell
The cytoplasm splits in two
DNA and other organelles replicate
Chromosomes are not visible
Two identical daughter cells are produced which are also identical to the parent cell

3. Chromosomes are not visible
DNA and other organelles replicate
Chromosomes become visible
Chromosomes line up along the centre of the cell
Chromosomes are pulled apart
Two new nuclei form
The cytoplasm splits in two
Two identical daughter cells are produced which are also identical to the parent cell

4. Learning Outcomes Recall the stages of mitosis
describe gametes as the scientific word for sex cells (sperm and eggs)
recall that meiosis is a type of cell division that produces gametes
understand why it is important that meiosis produces cells with only half the number of chromosomes of the original (parent) cell
Compare and contrast mitosis and meiosis

5. Every cell in the body is produced by mitosis….
…with the exception of two types of cells
What do you think these cells are?
Why?

6. Why can't sex cells
be produced
through mitosis?

7. Fertilisation 23 23
Zygote 46

8. Meiosis occurs .... Only occurs in gametogenic areas..
Males seminiferous tubules of testes
Females follicles in ovaries

9. Meiosis 2n
Haploid – containing 1 set of chromosomes (n) (half somatic cell) n n n n

10. Why are brothers and sisters not identical
Why are brothers and sisters not identical? Or sisters and sisters Or brothers and brothers

11. Crossing Over - chiasmata

12. So how does meiosis happen?

13. Put these in the correct order ....

14. ANSWERS

15. Meiosis The stages of meiosis are;
The chromosomes in the cell are copied (same as in mitosis).
All the homologous (the same type) chromosomes pair up. Cross over occurs
One from each pair move to opposite sides of the cell leading to 2 daughter cells being produced. These are diploid cells containing 23 pairs of chromosomes.
Each daughter cell then divides again to form 4 other daughter cells. These are the sex cells. They are haploid cells containing just 23 chromosomes.

16. What affect does the relative sizes of the male and female gametes on behaviour of individuals?
What is the difference between a haploid and a diploid cell?
Why is the egg cell bigger?
Why is in-breeding so harmful?
Since this is sexual reproduction, what is asexual reproduction?

17. Meiosis Mitosis V Mitosis Meiosis How many cell divisions?
How many daughter cells are produced?
What are they like compared to the parent cell?
What types of cells does this process produce?

18. Meiosis Mitosis V Mitosis Meiosis How many cell divisions?
How many daughter cells are produced?
What are they like compared to the parent cell?
What types of cells does this process produce?

19. Key Questions
What is the difference between a haploid and a diploid cell?
2. Since this is sexual reproduction, what is asexual reproduction?
3. Where does meiosis happen?

20. REview
Use relevent words to use each of the letters in meiosis
M E I O S I S P E R M

21. Which stage is this?