1. Meiosis
Noadswood Science, 2016

2. Meiosis
Sunday, May 27, 2018
To explain the process of meiosis

3. Precise Learning
Students should understand that meiosis leads to non-identical cells being formed while mitosis leads to identical cells being formed.
Students should be able to explain how meiosis halves the number of chromosomes in gametes and fertilisation restores the full number of chromosomes.
Cells in reproductive organs divide by meiosis to form gametes.
Gametes join at fertilisation to restore the normal number of chromosomes. The new cell divides by mitosis. The number of cells increases. As the embryo develops cells differentiate (knowledge of the stages of meiosis is not required)

4. Recapping Mitosis
Mitosis is the type of cell division that leads to growth or repair
When a cell divides by mitosis: -
Two new cells form
Each cell is identical to the other one, and the cell they were formed from

5. Mitosis Stages Parent cell
Chromosomes make identical copies of themselves
They line up along the centre
They split
They move apart
Two daughter cells form with identical chromosomes to the parent cell

6. Meiosis
Gametes are formed from cells in the reproductive organs by a type of cell division called meiosis
Male
Female
Reproductive Organs
Testes
Ovaries
Gametes
Sperm
Egg

7. Meiosis
The cells that are formed by meiosis have half as many chromosomes as the cell that formed them
Human body cells contain 23 pairs of chromosomes, while human gametes contain 23 single chromosomes
The main features of meiosis are: -
The chromosomes are copied
The cell divides twice, forming four gametes

8. Meiosis Stages

9. Meiosis

10. Meiosis

11. Gender
Human body cells have 23 pairs of chromosomes in the nucleus – one of these pairs controls the inheritance of gender (whether offspring are male or female)
In males, the two sex chromosomes are different – XY
In females, the two sex chromosomes are the same – XX
Male – XY
Female – XX

12. Gametes & Fertilisation
Gametes are sex cells – the male gametes are the sperm, and the female gametes are the eggs
Gametes contain one set of genetic information, while body cells contain two sets of genetic information
Fertilisation is the joining or fusion of a male gamete and a female gamete – the new cell that is formed divides over and over again by mitosis creating the many cells that eventually form a new individual

13. Observations
Using the microscopes look at some cells which are currently undergoing mitosis / meiosis…

14. Meiosis & Mitosis Comparison

15. Practice Questions How many sets of chromosomes do gametes have?
Where are gametes produced?
How many cell divisions occur in meiosis?
How many new cells are produced when a cell divides by meiosis?
True or false – all gametes are genetically identical
Following fertilisation, how does the resulting cell grow?

16. Answers How many sets of chromosomes do gametes have – 1
Where are gametes produced – reproductive organs
How many cell divisions occur in meiosis – 2
How many new cells are produced when a cell divides by meiosis – 4
True or false – all gametes are genetically identical – false
Following fertilisation, how does the resulting cell grow – via mitosis