Meiosis Catalyst:  DESCRIBE what type of cells mitosis occurs in.  Somatic cells are 2N. EXPLAIN what this means.  EXPLAIN why it is important for cells to copy all their DNA during mitosis and become 4N.  Gametes are created through a process called meiosis. Gametes, though, are 1N. DESCRIBE what type of cells gametes are. EXPLAIN what 1N means. INFER why gametes are only 1N. FIRST FIVE.

Meiosis Review  What type of cells does mitosis occur in?  Mitosis occurs in somatic cells.  Somatic cells are 2N. What does this mean?  2N means there are two of each type of chromosome.  Why is it important that cells copy all their DNA during mitosis, and become 4N?  It is important that cells copy all their DNA during mitosis and become 4N because the cell splits in half. When the parent cell splits in half, the daughter cells will still have 2N, an exact copy of the parent cell.

Agenda  Catalyst  Meiosis  BRAIN GAIN  Comparing meiosis to mitosis  EQ

Objectives By the end of today, SWBAT…  Explain the purpose of meiosis  Compare and contrast mitosis and meiosis

Review of Mitosis  Somatic cells have 2 of each type of chromosome  Mitosis produces cells that are 2N. 2N → 4N 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, sperm)  Meiosis is for sexual reproduction How is this different from mitosis?

New Vocabulary  Somatic cells have 2 of each type of chromosome (2N).  Have all the instructions necessary to make an organism.  Somatic cells are diploid. (2N)  Gametes only have 1 of each type of chromosome (1N).  Only have HALF of the DNA necessary to make an organism.  Gametes are haploid. (1N)

1N =2N Now does it makes sense why you need one sperm and one egg?

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 4N 1N 2N You don’t want a baby with 4N!!!!!! 2N is the regular number of chromosomes!

 In meiosis, there are two rounds of cell division 2N → 4N So how does this work? 2N 1N MEIOSIS IMEIOSIS II

How does this work?  In meiosis, there are two rounds of cell division 2N 4N 2N2N 1N 1N1N 1N MEIOSIS I MEIOSIS II How is this different from mitosis?

Waaaaait a second. Why is it important for gametes to go through a second round of cell division?

Family Matters  Meiosis can explain a lot of things in life… Why am so much better looking than my brother, even though we have the same parents?

Thank you, meiosis!

NOT IDENTICAL  Key Point #3: Meiosis produces genetically DIFFERENT cells.  Genetic information between chromosomes gets switched. Germ Cell

More Meiosis

A Closer Look Start: 2N 1N How is this different from mitosis?

Hold Up Check Our Understanding…. 1.Describe the difference between haploid and diploid cells. 2.Compare and contrast the function of mitosis and meiosis. 3.Explain why it is important that gamete cells go through a second round of cell division. 4.Explain why Shirley and her sister, Sheryl, don’t look identical.

Guided Practice Meiosis produces… a) Identical cells b) Different cells c) 23 types of cells d) Two copies of each cell

Guided Practice Meiosis occurs in… a) Somatic cells b) Gametes c) Chromosomes d) All eukyarotic cells

Guided Practice How many times do cells divide in meiosis? a) 1 b) 2 c) 3 d) 4

Guided Practice The cells produced by meiosis are _____, also known as ______. a) Haploid… 1N b) Diploid… 1N c) Haploid… 2N d) Diploid… 2N

Guided Practice Gametes have _____ copy/copies of each type of chromosome. a) 1 b) 2 c) 23 d) 46

Guided Practice What would happen if gametes were 2N? a) Children would be 2N, and die b) Children would be 4N, and have superpowers c) Children would be 4N, and die d) 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 cells b) Two copies of each cell c) Identical cells d) 23 types of cells

Guided Practice Meiosis occurs in… a) Chromosomes b) Somatic cells c) All eukyarotic cells d) Gametes

Guided Practice How many times do cells divide in meiosis? a) 4 b) 3 c) 2 d) 1

Guided Practice The cells produced by meiosis are _____, also known as ______. a) Haploid… 1N b) Haploid… 2N c) Diploid… 1N d) Diploid… 2N

Guided Practice Gametes have _____ copy/copies of each type of chromosome. a) 2 b) 46 c) 23 d) 1

Guided Practice What would happen if gametes were 2N? a) Children would be 4N, and die b) Children would be 4N, and have superpowers c) Trick question, gametes are 2N! d) Children would be 2N, and die

Step Yo’ Game Up!  So here’s the dillio:  We need to be able to COMPARE meiosis and mitosis

Put in your notes….YOU TRY 3 MINS MITOSISMEIOSIS SOMATIC CELLS OR GAMETES? HAPLOID OR DIPLOID? 2N OR 1N? IDENTICAL CELLS OR DIFFERENT CELLS? 1 OR 2 DIVISIONS?

ANSWERS MITOSISMEIOSIS SOMATIC OR GAMETES? somaticgametes HAPLOID OR DIPLOID? diploidhaploid 2N OR 1N? 2N1N IDENTICAL CELLS OR DIFFERENT CELLS? identicaldifferent 1 OR 2 DIVISIONS? 1 division2 divisions

IMMA GENIUS DIRECTIONS: Using all the words to the right, write one paragraph comparing and contrasting mitosis and meiosis. WORD BANK One cell division1N Two cell divisions2N Body CellsHaploid Sex CellsDiploid ReproductionGrowth Chromosome(s)

IMMA GENIUS!  Using your knowledge of MITOSIS and MEIOSIS, create a DOUBLE BUBBLE to compare and contrast the two. How many bubbles can you add?

Guided Practice Produces cells with 2N chromosomes a) Mitosis b) Meiosis

Guided Practice Creates diploid cells a) Mitosis b) Meiosis

Guided Practice Produces four DIFFERENT daughter cells a) Mitosis b) Meiosis

Guided Practice Creates cells with 1N chromosomes a) Mitosis b) Meiosis

Guided Practice Genetic information between chromosomes gets switched a) Mitosis b) Meiosis

Guided Practice Which of the following is true? A) There are more cell divisions in mitosis than meiosis B) There are more cell divisions in meiosis than mitosis C) There are the same number of cell divisions in both D) The cell does not divide in mitosis or meiosis

Guided Practice Mitosis occurs in _____, meiosis occurs in _____ a) Animals… Animals and plants b) Gametes… somatic cells c) Eukaryotic cells… prokaryotic cells d) Somatic cells… gametes

Guided Practice Mitosis produces _____ cells, meiosis produces _____ cells. a) Haploid… diploid b) Gametes… somatic c) Eukaryotic… prokaryotic d) 1N… 2N

Word hard, get smart.  Meiosis worksheet.  When you are done:  Cellular Reproduction study guide!  Mitosis vs. Meiosis Honors Work (in honors bin)  If you are having trouble, NOW is the time to get help. We have a QUIZ tomorrow.

Exit Questions 1. Explain the function of meiosis. 2. Describe the final products of meiosis.  Tell me EVERYTHING you know about what meiosis creates. 3. Use your knowledge of meiosis to explain why siblings with the same mom and dad aren’t identical. Complete sentences! Don’t talk!

Women only produce one viable egg in meiosis, the other three cells are polar bodies that will be destroyed. Women only produce a few hundred eggs over the course of their entire lives. Oogenesis

Spermatogenesis Men are busy – meiosis produces roughly 250,000,000 sperm per day!!!