Meiosis

Catalyst: What type of cells does mitosis occur in?

How many times does the cell divide during mitosis?

Write in complete sentences!

Don’t talk during the Catalyst!

Objectives

By the end of today, SWBAT…

State the purpose of meiosis

Compare mitosis and meiosis

Review of Mitosis

Somatic cells have 2 of each type of chromosome Mitosis produces cells that are 2N.

2N→4N2N

2N

Review of Mitosis

But wait…

There’s another type of cell division for one specific purpose!

Meiosis

Key Point #1: Meiosis is cell division for gametes. Gametes = sex cells (eggs for women and sperm for men)

Meiosis is for sexual reproduction

New Vocabulary

Somatic cells have 2 of each type of chromosome (2N). This means that somatic cells have all the instructions necessary to make an organism. Another word for 2N is diploid. Somatic cells are diploid.

Gametes only have 1 of each type of chromosome (1N). This means that they only have HALF of the DNA necessary to make an organism. Another word for 1N is haploid. Gametes are haploid.

Now it makes sense why

you need one sperm and

one egg, right???

Why?

Key Point #2: Gametes must be haploid (1N) Every human must have two copies of each chromosome If gametes were diploid (2N), the child would not survive

2N

2N4N

1N

1N

2N

You don’t want a

baby with 4N!!!!!!

2N is the regular

number of chromosome

s!

In meiosis, there are two rounds of cell division

2N→4N

So how does this work?

2N

2N

1N

1N

1N

1N

MEIOSIS I MEIOSIS II

Family Matters

Meiosis can explain a lot of things in life…

Especially the age-old question…

Why am I look so much better looking than my sister, even though we have the same parents?

Thank you, meiosis!

NOT IDENTICAL

Key Point #3: Meiosis produces genetically DIFFERENT cells. Why different? Genetic information between

chromosomes gets switched.

Germ Cell

More Meiosis

A Closer Look2N

1N

1N 1N

1N

Take a step back

Can someone tell me what mitosis is for?

Can someone tell me what meiosis is for?

What’s the difference between haploid and diploid?

Why is it important that gametes are haploid?

ActivExpression Practice!

Guided Practice

Meiosis produces…a)Identical cellsb)Different cellsc)23 types of cellsd)Two copies of each cell

Guided Practice

Meiosis occurs in…a)Somatic cellsb)Gametesc)Chromosomesd)All eukyarotic cells

Guided Practice

How many times do cells divide in meiosis?

a)1b)2c)3d)4

Guided Practice

The cells produced by meiosis are _____, also known as ______.

a)Haploid… 1Nb)Diploid… 1Nc)Haploid… 2Nd)Diploid… 2N

Guided Practice

Gametes have _____ copy/copies of each type of chromosome.

a)1b)2c)23d)46

Guided Practice

What would happen if gametes were 2N?

a)Children would be 2N, and dieb)Children would be 4N, and have

superpowersc) Children would be 4N, and died)Trick question, gametes are 2N!

Were You Paying Attention?

I’m going to ask the same questions again!

Answers are scrambled

Guided Practice

Meiosis produces…a)Different cellsb)Two copies of each cellc)Identical cellsd)23 types of cells

Guided Practice

Meiosis occurs in…a)Chromosomesb)Somatic cellsc)All eukyarotic cellsd)Gametes

Guided Practice

How many times do cells divide in meiosis?

a)4b)3c)2d)1

Guided Practice

The cells produced by meiosis are _____, also known as ______.

a)Haploid… 1Nb)Haploid… 2Nc)Diploid… 1Nd)Diploid… 2N

Guided Practice

Gametes have _____ copy/copies of each type of chromosome.

a)2b)46c)23d)1

Guided Practice

What would happen if gametes were 2N?

a)Children would be 4N, and dieb)Children would be 4N, and have

superpowersc) Trick question, gametes are 2N!d)Children would be 2N, and die

Step Yo’ Game Up!

So far, we’ve only been talking about meiosis

On the test, you will have to COMPARE meiosis and mitosis

Put in your notes….YOU TRY 2 MINS

MITOSIS MEIOSISSOMATIC OR GAMETES?

HAPLOID OR DIPLOID?

2N OR 1N?

IDENTICAL OR DIFFERENT?

1 OR 2 DIVISIONS?

ANSWERS

MITOSIS MEIOSISSOMATIC OR GAMETES? somatic gametes

HAPLOID OR DIPLOID? diploid haploid

2N OR 1N? 2N 1NDIFFERENT OR

IDENTICAL? identical different

1 OR 2 DIVISIONS? 1 division 2 divisions

Back to ActivExpression

Guided Practice

Produces cells with 2N chromosomes

a)Mitosisb)Meiosis

Guided Practice

Creates diploid cells

a)Mitosisb)Meiosis

Guided Practice

Produces four DIFFERENT daughter

cells

a)Mitosisb)Meiosis

Guided Practice

Creates cells with 1N chromosomes

a)Mitosisb)Meiosis

Guided Practice

Genetic information between chromosomes

gets switched

a)Mitosisb)Meiosis

Guided Practice

Which of the following is true?A)There are more cell divisions in mitosis

than meiosisB)There are more cell divisions in

meiosis than mitosisC)There are the same number of cell

divisions in bothD)The cell does not divide in mitosis or

meiosis

Guided Practice

Mitosis occurs in _____, meiosis occurs in _____

a)Animals… Animals and plantsb)Gametes… somatic cellsc)Eukaryotic cells… prokaryotic cells

d)Somatic cells… gametes

Guided Practice

Mitosis produces _____ cells, meiosis produces _____ cells.

a)Haploid… diploidb)Gametes… somaticc)Eukaryotic… prokaryoticd)1N… 2N

Independent Practice/HW

Exit Questions

What is the purpose of meiosis? How many cells does meiosis

produce? Why is Mr. J so much better

looking than his sister? (Hint: it has to do with sperm and egg cells.)

Write in complete sentences!

Don’t talk during the Catalyst!