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MeiosisMeiosis

L.O: To understand meiosis and how the sex cells determine

gender

Can you identify what this Can you identify what this picture is showing?picture is showing?

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Meiosis – another type of cell division!

http://www.youtube.com/watch?v=D1_-mQS_FZ0

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20/04/23 What is meiosis?What is meiosis?

Meiosis begins with a single cell. (23 chromosome pairs)

First the cell makes a copy of each chromosome. (92 chromosomes in total)

During the first division the pairs a split up.(l46 chromosomes in each)

original cell

firstdivision

seconddivision

4 new cells

Now the chromosome copies split from the original.The new cells contain half the genetic information and unpaired chromosomes(23 chromosomes in each)

20/04/23 Meiosis Meiosis animationanimation

Look at the meiosis microscope slide. Draw and explain what you can see.

Why can’t we look at a normal body cell to see meiosis

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20/04/23 What type of cells are formed by What type of cells are formed by meiosis?meiosis?

In animals, meiosis produces ova in females and sperm cells in males.

In plants, the gametes produced by meiosis are pollen grains and ovules.

Sexual ReproductionSexual Reproduction

The human egg and sperm cell

(“GAMETES”) contain 23

chromosomes each and are created by

meiosis.

When fertilisation happens the gametes fuse together to

make a single cell called a ZYGOTE. The zygote has 46 chromosomes (23 pairs) and continues to grow through

mitosis.

20/04/23 Meiosis activityMeiosis activity

What are the main differences between mitosis

and meiosis

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Mitosis vs. MeiosisMitosis vs. MeiosisMitosis:

1. Used for growth and repair of cells

2. Used in asexual reproduction

3. Cells with identical number of chromosomes and genetic information are produced

Meiosis:

1. Used to produce gametes for sexual reproduction

2. Each daughter cell has half the number of chromosomes of the parent

Tick or cross to indicate whether the Tick or cross to indicate whether the feature applies to meiosis, mitosis or feature applies to meiosis, mitosis or

bothbothFeature Mitosis Meiosis

Occurs in growth and repair

Movement of chromosomes occurs

Daughter cells are identical to the parent cell

Chromosome number is halved

Produces haploid cells from diploid cells

Daughter cells can be different from each other

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Worksheets

How do chromosomes in How do chromosomes in gametes determine sex?gametes determine sex?

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What does this picture show?

What does this picture show?

Boy or Girl?Boy or Girl?

X Y X

XX XYGirlBoy

“Allele”

20/04/23 Stages of mitosis activityStages of mitosis activity

20/04/23 Stages of meiosis activityStages of meiosis activity

20/04/23 Mitosis or meiosis?Mitosis or meiosis?

20/04/23 Who wants to have a million Who wants to have a million cells?cells?

FLASH 2 – Mitosis drag & drop