Meiosis Notes

Foldable

• You need 6 pieces of paper.

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• Stagger the pages about 1cm (width of pinky finger).�DO NOT make the tabs too large!!!!!

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• Fold the stack of pages to make the foldable as shown on the next slide.

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• On the cover write “MEIOSIS”.

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• On the back put your Name and Period.

Foldable Layout

• Label the tabs of the foldable according to the diagram to the right

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• Use some way�(choice is yours)�to show which tabs make up Meiosis I and which tabs make up Meiosis II

Vocabulary (11^th tab)

Meiosis

Meiosis Introduction

Interphase

Prophase I

Metaphase I

Anaphase I

Telophase I & Cytokinesis

Prophase II

Metaphase II

Anaphase II

Telophase II & Cytokinesis

Vocabulary & Useful facts

Meiosis I

Meiosis II

Note Taking Key

• Text in black will be copied into your flipbook

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• Vocabulary words will be like this 🡪 Meiosis�Highlight these in your notes, you will define these in the back of your foldable.

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• Interesting facts will have slide Headings and text in blue like this 🡪 Mitosis vs Meiosis�

You do not have to copy blue text into your flipbook unless you want to.

Mitosis Diagram

There is not room for you to draw this diagram, but know what it means

Meiosis vs Mitosis

Mitosis creates 2 identical daughter cells (diploid )

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Meiosis creates 4 genetically different gametes (haploid)

Meiosis Introduction (1^st tab upper half)

• Process of reduction division

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• Purpose: Produces gametes

(sex cells) – sperm & egg�

• Meiosis is NOT a cycle like mitosis.

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Diploid vs. Haploid

• Diploid – a cell that contains homologous chromosomes (one from each parent) ��represented by the symbol 2N
• Found in somatic or body cells (ex. Skin, digestive tract)
• Example : Humans 🡪 2N = 46

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• Haploid – a cell that contains only a single set of chromosomes (one from either parent, not both); ��represented by the symbol N or 1N
• Found in gametes or sex cells – sperm & egg
• Example: Humans 🡪 N = 23

Meiosis Introduction (1^st tab middle)�Chromosome Numbers

• Somatic cells: (diploid = 2N = 46 chromosomes in humans)�
• Gametes: (haploid = N = 23 chromosomes in humans)

You DO NOT�have to draw these pictures on the �1^st tab for �Meiosis Introduction

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Just write the Somatic and Gamete info above

Chromosome Numbers of Some Common Organisms

Meiosis Introduction (1^st tab middle)

• Similar to Mitosis’ IPMATC

• Meiosis involves two distinct divisions, called Meiosis I and Meiosis II.�
• By the end of Meiosis II, the 1 diploid cell that entered meiosis has become 4 haploid cells.

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Meiosis Introduction (1^st tab bottom half)

• Glue the smaller diagram at the bottom.

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Interphase

Prophase 1

Metaphase 1

Anaphase 1

Telophase 1 &

Cytokinesis

Meiosis 1

Prophase 2

Metaphase 2

Anaphase 2

Telophase 2 &

Cytokinesis

Meiosis 2

Interphase (2^nd tab)

• Stage between divisions

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• Contains: centrioles and chromatin

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• Made of stages: �G1 – basic cell growth�S – replication and repair of DNA�G2 – final preparation for cell division

Centrioles

Nucleus �(with chromatin)

Glue and label this picture in your flipbook.

Meiosis I

• (You do not need to draw these, just showing you the stages)

Prophase I �(3^rd tab – upper half)

• Corresponding homologous chromosomes from each parent pair up to form homologous pairs

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• When homologous chromosome overlap its called crossing over.

Homologous Pairs�(Humans have 23 pairs making 46 total chromosomes)

Centrioles

Spindle�fibers

Glue and label this picture in your flipbook.

Prophase I�(3^rd tab lower half)

• Crossing over happens when parts of the homologues chromosomes switch places after overlapping.

Glue this diagram and use 2 different colors to show the exchanged genetic material

How can siblings look alike but not exactly the same if they come from the same parents?

Importance of crossing over

• The gene combinations that a person gets from his or her parents will be different, to varying degrees, than the combination a sibling may get.

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• Crossing over increases genetic diversity

Add this statement to the Prophase 1 page on the 3^rd tab.

More sibling similarities

Metaphase I (4^th tab)

Homologous Pairs�

Centrioles

Spindle�fibers

Glue and label this picture in your flipbook.

Anaphase I (5^th tab upper half)

• The centrioles use�the spindle fibers to separate the�homologous pairs.�
• Each homologous chromosome is pulled to the opposite pole�of the cell.

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Homologous Chromosomes�

Centrioles

Spindle�fibers

Draw and label this picture in your flipbook

Anaphase I (5^th tab upper half)

• If the centrioles do not properly attach the spindle fibers to the homologous chromosome before they start to pull, then a Nondisjunction will occur

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Homologous Chromosomes�

Centrioles

Spindle�fibers

Glue and label this picture in your flipbook.

Anaphase I (5^th tab lower half)�Nondisjunction in Meiosis I

• In the first picture you see how the lower red chromosome is being pulled to the wrong side
• In the second picture it caused one pole of the cell to have an extra chromosome
• A Nondisjunction causes the gametes to have the wrong amount of chromosomes

Telophase I & Cytokinesis�(6^th tab)

• Telophase I – the cell creates a temporary nucleus around the two homologous chromosome sets
• Cytokinesis – the cell divides into two cells

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Homologous Chromosomes�

Centrioles

Nuclear Membrane

Glue and label this picture in your flipbook.

Prophase II (7^th tab)

• The next slide has information about starting Meiosis II.

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• Write this information on the Prophase II (7^th tab upper half) and draw a box around it.

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• You do not have to draw the picture for all of Meiosis II because you’ll draw each stage individually.

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• The lower half of the 7^th tab will be Prophase II. Describe and diagram that slide

Meiosis II (7^th tab upper half)

• The two new cells produced by meiosis I now enter a second meiotic division.�
• The cells do NOT replicate DNA, resulting in four haploid cells.�

• Each cell has half of the original DNA.�
• 2N ÷ 2 = N

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Prophase II (7^th tab lower half)

• Each of the Meiosis II stages are running in 2 cells at the same time.

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• Similar to Prophase of Mitosis

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• Centrioles attach spindle fibers to the chromosomes

Centrioles

Spindle�fibers

Chromosomes

Glue and label this picture in your flipbook.

Metaphase II (8^th tab)

• Similar to Metaphase of Mitosis

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• Centrioles use spindle fibers to line up the chromosomes in the middle at the metaphase plate

Centrioles

Spindle�fibers

Chromosomes

Glue and label this picture in your flipbook.

Anaphase II (9^th tab upper half)

• The centrioles use�the spindle fibers to separate the�chromosomes into individual chromatids�
• Each chromatid is pulled to the opposite pole of the cell

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Chromatids

Centrioles

Spindle�fibers

Glue and label this picture in your flipbook.

Anaphase II (9^th tab upper half)

• If the centrioles do not properly attach the spindle fibers to the chromosome before they start to pull, then a Nondisjunction will occur

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Chromatids

Centrioles

Spindle�fibers

Glue and label this picture in your flipbook.

Anaphase II (9^th tab lower half)�Nondisjunction in Meiosis II

• In the third picture you see how the lower red chromosome only has one spindle fiber attached
• In the fourth picture it caused one gamete to have an extra chromatid and the other gamete to be missing one.
• A Nondisjunction causes the gametes to have the wrong amount of chromosomes

Telophase II & Cytokinesis�(10^th tab)

• Telophase II – the cells create a permanent nucleus around the two haploid chromosome sets
• Cytokinesis – the cells divide into four haploid daughter cells

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Chromatids

Nuclear Membrane

Glue and label this picture in your flipbook.

Gamete (Sex Cell) Formation

• In male animals (including humans), the haploid gametes produced by meiosis are called sperm

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• 4 sperm cells are produced from one meiotic division

Gamete (Sex Cell) Formation

• In female animals (including humans), the haploid gametes produced by meiosis are called eggs

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• The cell divisions at the end of meiosis I & II are uneven, so that 1 large egg is produced along with 3 other cells, called polar bodies, which are discarded and not involved in reproduction

Meiosis Animation

• The following slide shows a simple animation using a cell with 2 pairs of homologous chromosomes going through meiosis.

Meiosis Animation

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Meiosis I Animation

http://wps.prenhall.com/wps/media/objects/487/498728/CDA9_1/CDA9_1b/CDA9_1b.htm

Meiosis II Animation

http://wps.prenhall.com/wps/media/objects/487/498728/CDA9_1/CDA9_1c/CDA9_1c.htm

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Vocabulary & Useful Info (11^th tab)

• This tab will contain vocabulary, a table and some useful facts

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• Set up the page like the diagram to the right

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• The dotted blue line is the fold in the middle of the page

Vocabulary (11^th tab)

Vocabulary section�(there are 15 words so size accordingly)

Vocabulary & Useful Info

Mitosis vs Meiosis Table�(The next couple of �slides contain the �info for this table)

Useful Facts

Vocabulary (11^th tab upper half)

Reduction division – When the number of chromosomes per cell is cut in half

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Haploid – A cell that has half the amount of chromosomes. � A cell that is “N” for chromosome amount

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Diploid – A cell that has twice the amount of chromosome. � A cell that is “2N” for chromosome amount

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Gamete – the haploid “sex” cells (in animals they are sperm and egg cells)

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Somatic Cell – all diploid cells (body cells) that are not gametes

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Zygote – fertilized egg cell formed form the joining of the gametes (sperm and egg)

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Vocabulary (11^th tab upper half)

Centrioles – Organelles in the cell that help to move chromosomes during cell division

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Chromatin – What you call the DNA during Interphase, Very easy to access the genes for transcription and translation to create proteins

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Chromosome – What you call the DNA during the actual cell division stages (Pro-, Meta-, Ana-, and Telophase). � Condensed/packed DNA for easy movement during cell division

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Chromatid – One of the “arms” of a chromosome ‘X’. Each chromatid is identical to the other because it is created by replication.� A chromosome is made of two Sister Chromatids.

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Spindle Fiber – fibers created and used by the centrioles to move the chromosomes around during the division stages.

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Vocabulary (11^th tab upper half)

Homologous Chromosomes – the same numbered chromosome that pair up from mother and father (ex: mom’s chromosome 1 and dad’s chromosome 1)

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Crossing Over – A kind of chromosomal mutation that happens in Prophase 1 of meiosis. � Homologous chromosomes overlap and exchange pieces of the� chromosome which caused genetic variability.

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Nondisjuction – Happens in either Anaphase 1 or Anaphase 2 of meiosis when one centriole does not connect to the chromosome with a spindle fiber.� Causes the gametes to have extra or missing chromosomes.

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Fertilization – The process of making a zygote. When egg and sperm cells fuse and combine their genetic information (DNA)

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Table (11^th tab lower half)

• Set up your table as shown

• Use the following slides to complete the table you just made.

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• The text is in blue so you don’t have to write it all, but you will have to include enough to complete the table.

Comparing Mitosis & Meiosis

• Number of cells at beginning of process
• Mitosis = 1 Diploid cell
• Meiosis = 1 Diploid Cell

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• Number of cells at the end of the process
• Mitosis = 2 Diploid Cells
• Meiosis = 4 Haploid Cells

Comparing Mitosis & Meiosis

• Number of chromosomes at the START
• Mitosis = 46 (Diploid, “two sets”)
• Meiosis = 46

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• Number of chromosomes at the END
• Mitosis = 46
• Meiosis = 23 (Haploid, “one set”)

Comparing Mitosis & Meiosis

• Is the genetic make-up of the daughter cells UNIQUE or IDENTICAL?

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• Mitosis produces 2 IDENTICAL CELLS

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• Meiosis produces 4 UNIQUE CELLS

Comparing Mitosis & Meiosis

• Type of cell in the human body that can undergo each phase

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• Mitosis produces Somatic BODY cells (skin)

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• Meiosis produces Gamete SEX cells (sperm or eggs)

Interesting Facts (11^th tab bottom)

• Females produce all their eggs at once, and store them at a very early age (They release one each month during menstruation)��Males make sperm constantly from puberty until they die.