Meiosis

The student will describe the process of meiosis.

Subobjective 1: The student will describe how haploid cells develop into mature gametes.

Subobjective 2: The student will compare autosomes to sex chromosomes and body cells to sex cells.

Subobjective 3: The student will compare and contrast meiosis I and meiosis II.

Lesson Objective

Vocabulary Overview

1. Gamete

2. Fertilization

3. Meiosis

4. Sperm

5. Egg

Ticket In!

List one similarity and one difference between mitosis and meiosis.

How is a body cell different than a sex cell?

Give an example of a haploid cell.

Click the numbers

Anticipation Guide

Meiosis produces genetically identical cells.

Diploid cells have twice as many chromosomes as haploid cells.

Crossover occurs in Meiosis I only.

The autosomes determine the sex of an individual.

Meiosis reduces the number of chromosomes in a cell.

Erase in the statement boxes

Fill in each box with the relevant information for the given vocabulary word.

Frayer Model

• Sex cells

• Females - eggs

• Males - sperm

• Contain DNA

• The cells that pass information onto offspring

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Frayer Model

Fill in each box with the relevant information for the given vocabulary word.

• The female gamete produced by the ovaries

• Ovum

• Used in reproduction

• Haploid

• One egg arises from meiosis

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Fill in each box with the relevant information for the given vocabulary word.

Frayer Model

• The male gamete produced in the testes

• Sperm cell

• Used in reproduction

• Haploid

• Four sperm arise from meiosis

Frayer Model

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• The fusion of an egg and a sperm

• Human egg and sperm combine.

• The nuclei in the egg and sperm fuse.

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Fill in each box with the relevant information for the given vocabulary word.

Frayer Model

• Creation of haploid gametes

• The process of dividing diploid cells into haploid cells

• Produces genetically identical cells • Essential for sexual reproduction• Takes place only at certain times during the life cycle

Body Cells vs. Gametes

Of which type of cell is the brain comprised?

Most of the cells that comprise your body

Contain a complete set of chromosomes

Not passed onto offspring

i.e.: skin cells, brain cells, eyeball cells, kidney cells

Only the cells that make up eggs and sperm

Contain half of a set of chromosomes

These cells are passed onto your children.

i.e.: sperm, eggs

Body Cells Sex Cells (Gametes)

click the pictures

Homologous Chromosomes

Are homologous chromosomes completely identical to each other? Why or why not?

The same is true for the chromosomes in your cells.

46If you had 23 pairs of socks, how many individual socks would you have?

Homologous Chromosomes

Scientists have created a chart that numbers these chromosomes.Erase in the box.

What do the different colors on the chromosomes represent?Click here

Circle the autosomes.

Chromosome pairs 1-22 are not related to the sex of the individual.

Autosomes

These chromosomes are responsible for the development and functionality of the organism. They are autosomes.

Click here

Sex Chromosomes

The 23rd and final pair of chromosomes is called the sex chromosomes.

These are not homologous chromosomes.

The sex (male or female) and development of sexual characteristics are determined by this set.

XX = Female XY = Male

X: larger sex chromosomecontains many genes not directly related to sex characteristics

Y - smaller sex chromosome responsible for the development of male sexual characteristics such as the testes

Diploid vs. Haploid

i.e.: sex cells

Haploid (n): The cell has 1 copy of each chromosome

i.e.: body cells

Diploid (2n): The cell has 2 copies of each chromosome. (homologous chromosomes)

1/2 + 1/2 = 1

1 + 1 = 1Circle the equation that best represents meiosis.

Click here to see examples.

This allows for variation within the same species

The number of chromosomes is unique to each species.

Meiosis reduces the number of chromosomes.

Why do our sex cells have to be haploid?

To ensure the correct number of chromosomes in the offspring

Importance of Meiosis

When learning about meiosis, you will hearabout chromosomes and chromatids. Do you know the difference?

Chromosomes vs. Chromatids

These are attached at the center by a centromere.

Each sister chromatid contains the information from just one parent.

Meiosis I

Meiosis I: separation of homologous chromosomes

End Result = 2 diploid cells

Erase above the line.

Can you spot the cell in Prophase I?

Crossover occurs and genes are exchanged between homologous chromosomes

Duplicated chromosomes condense and pair up.

Nucleus breaks down and centrioles start to produce spindle fibers.

Prophase I

Answer: F

Crossing Over

Click on the globe to watch an educational video online.

Homologous chromosomes attach to spindle fibers.

These chromosomes are aligned along the center so that each side has chromosomes from both parents

Chromosomes are aligned randomly to ensure genetic variability.

Can you spot the cell in Metaphase I?

Metaphase I

Homologous chromosomes are pulled apart toward each side of the cell.

Sister chromatids stay attached.

Can you spot the cell in Anaphase I?

Answer: H

Anaphase I

Spindle fibers break down.

Nuclear envelope reforms to contain chromatids.

Cytoplasm is divided (cytokinesis).

Can you spot the cell in Telophase I?

Telophase I

Answer: G

Result - 4 cellsEnd Result click here

Erase above the line.

Meiosis II

Meiosis II: separation of sister chromatids

Can you spot the cell in Prophase II?

Answer: I

Same process as Prophase I

However, there is no crossover.

Same process as Metaphase I.

This time, spindle fibers align sister chromatids.

Can you spot the cell in Metaphase II?

Metaphase II

Answer: D

Can you spot the cell in Anaphase II?

Sister chromatids are separated into each side of the cell.

Answer: B

Anaphase II

Same process as Telophase I.

During cytokinesis, the cytoplasm is divided.

Which would show the cell after cytokinesis?

Can you spot the cell in Telophase II?

Answer: C & A

Metaphase IITelophase II

Write the correct term on the line. Then match the picture with the phase.

Meiosis I vs. Meiosis II

Anaphase I:

Metaphase II:

Metaphase I:

Telophase II:

Prophase I:

Anaphase II:

Prophase II:

Telophase I:

An egg will always have an X chromosome and a sperm will have an X or a Y. Which gamete is responsible for determining the sex of a child?

Development of Gametes

Therefore, they must go through more changes.

Meiosis produces gametes that are unable to be fertilized.

Oogenesis:maturation of an egg

Spermatogenesis: maturation of sperm

Which row in the chart below indicates the correct process for each event indicated?

Answer D

Review Questions

A 1B 3

C 2D 4

Explain why it is important for gametes to be haploid cells.

Wrap Up

Teacher's Resources

Mitosis Vs .Meiosis Animation

Meiosis Animation

Mitosis & Meiosis Hangman