Meiosis
Chapter 10.1 and 11.3
Do Now
How is a baby made?
 On the cellular level, draw how a baby is
made. (NO PHALLIC SYMBOLS
PLEASE!)

Why does sex exist?


Sexual reproduction creates genetic
variability
Let’s Brainstorm…


How do we get our different traits?
What is the difference between
fraternal and identical twins?
Do Now
What is mitosis?
 What is meiosis?
 List 2 differences between the two?

Let’s define the following
words…


Meiosis:
 Sexual



Gamete:
 Sex



reproduction-production of gametes

Cells (eg...


Haploid:
 Half




the chromosome number (n)
1 of each pair of chromosomes (23)

Diploid:
2

of each type of chromo...
Chromosomes and Chromosome
Number
Human body cells have 46 chromosomes
 Each parent contributes 23 chromosomes
 Homologo...
Karyotype
Homologous Chromosomes
Same length
 Same centromere position
 Carry genes that control
the same inherited traits

Meiosis





The sexual life cycle
in animals involves
meiosis
Meiosis produces
gametes.
When gametes
combine in
fertil...
Cell Cycle
DNA
Replication

Prepare

Growth
Division
2N

2N
Mitosis

N

N

N

N

Meiosis

2N
Do Now


Label A, B, and C



(Hint same size, same
shape…)
Meiosis


2 Division
 Meiosis

I (separation of homologous
chromosomes)
 Meiosis II (separation of sister chromatids)
Interphase
Same as Mitosis (G1, S, G2)
 DNA- Chromatin
 Centrioles- located near the nucleus

Prophase I
Pairing of homologous chromosomes
occurs. (Synapsis)
 Each chromosome consists of two
chromatids.
 The nuclea...
Prophase I (cont.)
Crossing over produces exchange
of genetic information.
 Crossing over —chromosomal
segments are excha...
Metaphase I
Chromosome centromeres attach to
spindle fibers
 Homologous chromosomes line up at the
equator.

Anaphase I


Homologous chromosomes separate and
move to opposite poles
Telophase I
The spindles break down.
 Chromosomes uncoil and form two nuclei.
 The cell divides.

Prophase II


A second set of phases begins as the
spindle apparatus forms and the
chromosomes condense.
Metaphase II
A haploid number of chromosomes line of
at the equator
 Sister chromatids line up

Anaphase II
The sister chromatids are pulled
apart at the centromere by spindle
fibers
 Move toward the opposite poles of...
Telophase II
The chromosomes reach the poles, and the
nuclear membrane and nuclei reform.
Cytokinesis



Cytokinesis results in four haploid cells
Each with n number of chromosomes.
Animation


http://www.cellsalive.com/meiosis.htm
Animations on Meiosis


http://highered.mcgraw-hill.com/sites/0072437
Do Now: Label the phases of meiosis
Genetic Variability
Depending on how the
chromosomes line up at the
equator, four gametes with
four different combinations...
Genetic Variability Animation


http://highered.mcgraw-hill.com/sites/0072437
Review Spermatogenesis and oogenesis


Think – Pair - Share

Draw out the stages of meiosis using the
following cell. Make sure you draw the cell with
crossin...
Do Now – Period 3
How many
autosomes?
 How many sex
chromosomes?
 What is the sex of
this patient?
 Monosomy,
Trisomy?
...
Do Now


Match the description to the phase of meiosis.

1. Sister Chromatids are pulled
apart. _____

A. Prophase I

2. ...
Review


How does meiosis promote genetic
variability? List 3 reasons why.
THINK – PAIR - SHARE


If a hamster has 44 chromosomes in G1
phase of the cell cycle, then…
 How

many chromatids are in...
Do Now
What two divisions do your cells undergo?
 What are the differences between the
two?

Meiosis glencoe
Meiosis glencoe
Meiosis glencoe
Meiosis glencoe
Meiosis glencoe
Meiosis glencoe
Meiosis glencoe
Meiosis glencoe
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Meiosis glencoe

  1. 1. Meiosis Chapter 10.1 and 11.3
  2. 2. Do Now How is a baby made?  On the cellular level, draw how a baby is made. (NO PHALLIC SYMBOLS PLEASE!) 
  3. 3. Why does sex exist?  Sexual reproduction creates genetic variability
  4. 4. Let’s Brainstorm…  How do we get our different traits?
  5. 5. What is the difference between fraternal and identical twins?
  6. 6. Do Now What is mitosis?  What is meiosis?  List 2 differences between the two? 
  7. 7. Let’s define the following words…  Meiosis:  Sexual  Gamete:  Sex  reproduction-production of gametes Cells (egg and sperm) haploid Somatic Cells:  Body Cells - diploid
  8. 8.  Haploid:  Half   the chromosome number (n) 1 of each pair of chromosomes (23) Diploid: 2 of each type of chromosome (2n)  Twice the haploid number  Fertilization:  Sperm  enters egg Zygote:  Fertilized egg (diploid)
  9. 9. Chromosomes and Chromosome Number Human body cells have 46 chromosomes  Each parent contributes 23 chromosomes  Homologous chromosomes —one of two paired chromosomes, one from each parent 
  10. 10. Karyotype
  11. 11. Homologous Chromosomes Same length  Same centromere position  Carry genes that control the same inherited traits 
  12. 12. Meiosis    The sexual life cycle in animals involves meiosis Meiosis produces gametes. When gametes combine in fertilization, the number of chromosomes is restored.
  13. 13. Cell Cycle DNA Replication Prepare Growth Division 2N 2N Mitosis N N N N Meiosis 2N
  14. 14. Do Now  Label A, B, and C  (Hint same size, same shape…)
  15. 15. Meiosis  2 Division  Meiosis I (separation of homologous chromosomes)  Meiosis II (separation of sister chromatids)
  16. 16. Interphase Same as Mitosis (G1, S, G2)  DNA- Chromatin  Centrioles- located near the nucleus 
  17. 17. Prophase I Pairing of homologous chromosomes occurs. (Synapsis)  Each chromosome consists of two chromatids.  The nuclear envelope breaks down.  Spindles form 
  18. 18. Prophase I (cont.) Crossing over produces exchange of genetic information.  Crossing over —chromosomal segments are exchanged between a pair of homologous chromosomes. 
  19. 19. Metaphase I Chromosome centromeres attach to spindle fibers  Homologous chromosomes line up at the equator. 
  20. 20. Anaphase I  Homologous chromosomes separate and move to opposite poles
  21. 21. Telophase I The spindles break down.  Chromosomes uncoil and form two nuclei.  The cell divides. 
  22. 22. Prophase II  A second set of phases begins as the spindle apparatus forms and the chromosomes condense.
  23. 23. Metaphase II A haploid number of chromosomes line of at the equator  Sister chromatids line up 
  24. 24. Anaphase II The sister chromatids are pulled apart at the centromere by spindle fibers  Move toward the opposite poles of the cell. 
  25. 25. Telophase II The chromosomes reach the poles, and the nuclear membrane and nuclei reform.
  26. 26. Cytokinesis   Cytokinesis results in four haploid cells Each with n number of chromosomes.
  27. 27. Animation  http://www.cellsalive.com/meiosis.htm
  28. 28. Animations on Meiosis  http://highered.mcgraw-hill.com/sites/0072437
  29. 29. Do Now: Label the phases of meiosis
  30. 30. Genetic Variability Depending on how the chromosomes line up at the equator, four gametes with four different combinations of chromosomes can result (independent assortment).  Genetic variation also is produced during crossing over  Random fertilization. 
  31. 31. Genetic Variability Animation  http://highered.mcgraw-hill.com/sites/0072437
  32. 32. Review Spermatogenesis and oogenesis
  33. 33.  Think – Pair - Share Draw out the stages of meiosis using the following cell. Make sure you draw the cell with crossing over of only one pair of homologous chromosomes! (use colored pencils)
  34. 34. Do Now – Period 3 How many autosomes?  How many sex chromosomes?  What is the sex of this patient?  Monosomy, Trisomy?  Is this individual normal? 
  35. 35. Do Now  Match the description to the phase of meiosis. 1. Sister Chromatids are pulled apart. _____ A. Prophase I 2. Homologous chromosomes line up in the middle of the cell._____ B. Metaphase I 3. 2 daughter cells are formed ____ C. Telophase I 4. Nuclear membrane disappears__ D. Anaphase II 5. Nuclear membrane reforms around 4 cells ____ E. Anaphase I 6. Homologous chromosomes are pulled apart ____ F. Telophase II
  36. 36. Review  How does meiosis promote genetic variability? List 3 reasons why.
  37. 37. THINK – PAIR - SHARE  If a hamster has 44 chromosomes in G1 phase of the cell cycle, then…  How many chromatids are in G2 Phase?  How many chromosomes are in the G2 Phase?  How many chromosomes will be in each cell after it has gone through mitosis?
  38. 38. Do Now What two divisions do your cells undergo?  What are the differences between the two? 
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