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CHAPTER 11: INTRODUCTION TO GENETICS Standards B.1.8, B.1.21, B.1.28, B.1.29 Section 11.4: Meiosis

CHAPTER 11: INTRODUCTION TO GENETICS Standards B.1.8, B.1.21, B.1.28, B.1.29 Section 11.4: Meiosis

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Page 1: CHAPTER 11: INTRODUCTION TO GENETICS Standards B.1.8, B.1.21, B.1.28, B.1.29 Section 11.4: Meiosis

CHAPTER 11: INTRODUCTION TO GENETICS

Standards B.1.8, B.1.21, B.1.28, B.1.29

Section 11.4: Meiosis

Page 2: CHAPTER 11: INTRODUCTION TO GENETICS Standards B.1.8, B.1.21, B.1.28, B.1.29 Section 11.4: Meiosis

Section 11.4: Meiosis

ASEXUAL REPRODUCTION

SEXUAL REPRODUCTION

Page 3: CHAPTER 11: INTRODUCTION TO GENETICS Standards B.1.8, B.1.21, B.1.28, B.1.29 Section 11.4: Meiosis

SO, Where does the baby get its genetic material?

Sexual Reproduction = 2 Parents

Page 4: CHAPTER 11: INTRODUCTION TO GENETICS Standards B.1.8, B.1.21, B.1.28, B.1.29 Section 11.4: Meiosis

Section 11.4: Meiosis

IMPORTANT CONCEPT:

Because organisms get half of their chromosomes from mom and half from dad, the chromosomes from each parent MUST be divided in half before they can be passed on.

Page 5: CHAPTER 11: INTRODUCTION TO GENETICS Standards B.1.8, B.1.21, B.1.28, B.1.29 Section 11.4: Meiosis

Section 11.4: Meiosis

Homologous Chromosomes A matching pair of chromosomes that have the

same genes. One of these chromosomes comes from MOM. The other chromosome comes from DAD.

Every animal has a unique # of chromosomes.

Humans have 46 chromosomes.(23 from MOM, 23 from DAD)

Page 6: CHAPTER 11: INTRODUCTION TO GENETICS Standards B.1.8, B.1.21, B.1.28, B.1.29 Section 11.4: Meiosis

Section 11.4: Meiosis

Diploid Cell A cell that contains BOTH sets of

chromosomes (mom AND dad).(2 sets = diploid = 2N) All body cells!

Haploid Cell A cell that contains ONE set of chromosomes

(mom OR dad).(1 set = haploid = 1N) All sex cells!

Page 7: CHAPTER 11: INTRODUCTION TO GENETICS Standards B.1.8, B.1.21, B.1.28, B.1.29 Section 11.4: Meiosis

Section 11.4: Meiosis

Meiosis The process of reduction division in which

the number of chromosomes in a cell is cut in half.

Homologous chromosomes are separated in the process.

mom!dad!

Page 8: CHAPTER 11: INTRODUCTION TO GENETICS Standards B.1.8, B.1.21, B.1.28, B.1.29 Section 11.4: Meiosis

Section 11.4: Meiosis

There are TWO major divisions during meiosis.

Meiosis I Reduction Division Homologous chromosomes pair up to form

tetrads.

Page 9: CHAPTER 11: INTRODUCTION TO GENETICS Standards B.1.8, B.1.21, B.1.28, B.1.29 Section 11.4: Meiosis

Section 11.4: Meiosis

Meiotic “Crossing Over” Crossing over: The exchange of alleles

between homologous pairs while in tetrads.

Chromosomes “trade” information! **Increases Diversity**

Page 10: CHAPTER 11: INTRODUCTION TO GENETICS Standards B.1.8, B.1.21, B.1.28, B.1.29 Section 11.4: Meiosis

Section 11.4: Meiosis

There are TWO major divisions during meiosis.

Meiosis II This happens the SAME way as Mitosis!

During Meiosis II, the sister chromatids are pulled apart.

This results in 4 haploid daughter cells.

Page 11: CHAPTER 11: INTRODUCTION TO GENETICS Standards B.1.8, B.1.21, B.1.28, B.1.29 Section 11.4: Meiosis

Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.

The sister chromatids separate and move toward opposite ends of the cell.

Meiosis II results in four haploid (N) daughter cells.

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.

The sister chromatids separate and move toward opposite ends of the cell.

Meiosis II results in four haploid (N) daughter cells.

• This happens the SAME way as Mitosis!• During Meiosis II, the sister chromatids are pulled

apart, resulting in 4 haploid daughter cells.

Page 12: CHAPTER 11: INTRODUCTION TO GENETICS Standards B.1.8, B.1.21, B.1.28, B.1.29 Section 11.4: Meiosis

Section 11.4: Meiosis

Results in 2 genetically identical diploid cells.Allows organisms to grow and replace parts.

Results in 4 genetically different haploid cells.Sex cell (gamete) production.

MITOSIS MEIOSIS