Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.
BIOLOGY FORM 4
CHAPTER 5 PART 2
CELL DIVISION - MEIOSIS
REFRESHER MITOSIS
Mitosis – HD
Mitosis
????????
• What is the name of the process shown in
the video?
• Where does it occur?
• What is the significance of the pr...
MITOSIS VIDEO
MITOSIS & MEIOSIS
ACTIVITY
• Arrange the cards in the correct sequence
HOTS : Please explain what has
this got to do with cell division?
Planaria
SET INDUCTION
Meiosis+-+The+Continuation+of+Life-SD
Meiosis
• What does this
picture tell us
about meiosis?
• How is the
purpose of
meiosis different
from the purpose
of mito...
Where does meiosis
occur in a male and
a female human?
Inside testes in
a male and
ovaries in a
female.
Meiosis in Plant
Occurs in the
• ovary (female)
Ovary
Occurs in the
• anther (male)
Anther
Meiosis produces
reproductive cells
(gametes)
Sperm
&
Ovum
Pollen
grains
& Egg
cells
Meiosis is the process of nuclear div...
Significance of meiosis:
• Reduce chromosome number from
diploid (2n) to haploid (n).
• Promote genetic diversity (variati...
Which process restores the diploid
number of chromosomes?
Meiosis reduces the chromosome number;
Fertilisation restores the diploid number.
egg
sperm
meiosis
46
fertilisation
23
23...
Features of Meiosis
Meiosis includes two rounds of division – meiosis I and
meiosis II.
Meiosis I Meiosis II
Prophase I Pr...
During meiosis I,
homologous chromosomes
separate.
2n n
During meiosis II,
sister chromatids separate.
n n
[just like mito...
Meiosis I: Reduction Division
Nucleus Spindle
fibers
Nuclear
envelope
Early Prophase I
(Chromosome
number doubled)
Late
Pr...
Prophase I
Prophase I may last a long time.
Human males:
 about 1 week for prophase I
 1 month for entire meiotic cycle...
Prophase I
Interphase Prophase I
(Bivalents)
Tetrads Form in Prophase I
(each with sister chromatids)
Homologous
chromosomes join
to form a TETRAD
Synapsis
Crossing over: genetic recombination
between non-sister chromatids
Plural (chiasmata)
- sites of crossing
over
Crossing-Over
Crossing over produces variation in gametes
Prophase I
Early prophase
Homologous
chromosomes pair up
- synapsis.
Crossing over occurs.
Late prophase
Chromosomes sh...
The longer the chromosome, the more
chiasmata that can form
PROPHASE I
Metaphase I
Homologous
pairs of
chromosomes
align along the
equator of the cell
METAPHASE I
Anaphase I
Homologous pair
saparate and move to
opposite poles.
Sister chromatids remain
attached at their
centromeres.
ANAPHASE I
Telophase I
Nuclear membrane &
nucleolus reappear.
Spindle fibres disappears.
Cytokinesis divides cell into
two.
2 Daughte...
TELOPHASE I
MEIOSIS I
Meiosis I:
 chromosome number
has been cut in half
 end result: 2 haploid
cells
Meiosis II:
 Similar to mitosis
 DNA d...
Meiosis II:
Prophase II
Metaphase II
Anaphase II
Telophase II 4 Identical
haploid
cells
Meiosis II is
similar to mitosis
Prophase II
Nuclear membrane &
nucleolus fragments.
Spindle fibres forms.
Centrioles move to
opposite poles.
PROPHASE II
Metaphase II
Chromosomes align
along equator of cell.
METAPHASE II
Anaphase II
Sister chromatids
separate and
move to opposite
poles.
Equator
Pole
ANAPHASE II
Telophase II
Nuclear membrane &
nucleolus reappears.
Chromosomes become
long & thin (decondense).
Spindle fibre disappears...
TELOPHASE II
MEIOSIS II
Results of Meiosis
Gametes (egg &
sperm) form
Four haploid cells with
one copy of each
chromosome
Centromere remains
intact
Anaphase I is the
reduction division.
Meiosis II No
interphase II
(or very short -
no more DNA
replication)
Remember:
Meiosis II is
similar to mitosis
http://hi...
What phase of meiosis?
Telophase I or Telophase II?
Which stage?
VIDEO
How Meiosis Works
Genetic variation is almost infinite as a
result of meiosis
HOTS Question:
Name and describe TWO main advantages of
meiosis relative to mitosis. (4)
1) Creates new combinations of ge...
ACTIVITY
• Show the sequence of Meiosis I and
Meiosis II using plasticine on manila card.
• Check your arrangement of
mito...
Comparing
Meiosis I and
Meiosis II
Activity
Comparing
Mitosis and
Meiosis
Activity
VIDEO
2d Difference between mitosis and meiosis
The importance of meiotic cell
division
• Ensure the diploid number of chromosomes
is maintained
• Provides genetic variat...
Appreciating the movement of
chromosomes during mitosis and meiosis
• Asexual reproduction (mitosis) produces
offspring th...
Down Syndrome: A meiotic error
Cause: Nondisjunction during either:
anaphase I
anaphase II
anaphase I anaphase II
Homologous
chromosomes fail to
separate
Sister
chromatids fail
to separate
Down Syndrome: trisomy 21
• In humans, if both chromosome 21 homologues
go to the same pole, and the resulting egg is
fert...
DOWN SYNDROME
KARYOTYPE
The chance of having a Down syndrome child
goes up with maternal age
Egg is in center of picture
Many cumulus cells from
the ovary are seen around
the egg. This is a low
quality, oocyte from ...
Question:
The diagram below represents the karyotype of
a human.
a) Why does the
structure shown
in Figure 2 have
an X-sha...
Diagrams A, B and C below show the same stage
in mitosis, meiosis I and meiosis II in a plant cell.
a)Identify the stage s...
b) The cell in diagram A
has 20 units of DNA.
How many units of DNA
would there be in a cell
from this plant at the
end of...
Question:
The simplified diagram below shows a nucleus
from a cell of an insect.
a) Draw diagrams to show the two nuclei w...
b) Draw diagrams to show three different
nuclei which could be formed if the
cell divided by meiosis. (Assume that
no cros...
THE END
Genetic Variation in meiosis occurs in
three ways:
1. Crossing over: prophase I
2. Random orientation of bivalents:
metaph...
Crossing over does not create
new alleles, it simply recombines
existing ones in new ways.
Meiosis I
Meiosis II
NEW COMBIN...
2. Random orientation of bivalents
No. of different combinations: 2n
2n = 4
n = 2
No. of
combinations:
22 = 4
Suggest explanations for the following
observation.
Meiosis, unlike mitosis, is not considered to
form part of a cell cycl...
106
Gametogenesis
Oogenesis
or
Spermatogenesis
107
Spermatogenesis
Occurs in the
testes
Two divisions
produce 4
spermatids
Spermatids mature
into sperm
Men produce a...
108
Spermatogenesis in the
Testes
Spermatid
109
110
Oogenesis
Occurs in the ovaries
Two divisions produce 3 polar
bodies that die and 1 egg
Polar bodies die because of...
111
Oogenesis in the Ovaries
112
Oogenesis
Oogonium
(diploid)
Mitosis
Primary
oocyte
(diploid)
Meiosis I
Secondary
oocyte
(haploid)
Meiosis II
(if fert...
Question:
Read the passage below and insert the appropriate
terms from the table below in the blank spaces
provided. Note ...
When haploid gametes unite during ……………… the
resulting zygote is ………… having received one
chromosome of each pair from eac...
Biology form 4 chapter 5   cell dvision part 2 (meiosis)
Biology form 4 chapter 5   cell dvision part 2 (meiosis)
Biology form 4 chapter 5   cell dvision part 2 (meiosis)
Biology form 4 chapter 5   cell dvision part 2 (meiosis)
Biology form 4 chapter 5   cell dvision part 2 (meiosis)
Biology form 4 chapter 5   cell dvision part 2 (meiosis)
Upcoming SlideShare
Loading in …5
×

Biology form 4 chapter 5 cell dvision part 2 (meiosis)

11,318 views

Published on

Biology form 4 chapter 5 cell dvision part 2 (meiosis)

Published in: Education
  • Be the first to comment

Biology form 4 chapter 5 cell dvision part 2 (meiosis)

  1. 1. BIOLOGY FORM 4 CHAPTER 5 PART 2 CELL DIVISION - MEIOSIS
  2. 2. REFRESHER MITOSIS Mitosis – HD Mitosis
  3. 3. ???????? • What is the name of the process shown in the video? • Where does it occur? • What is the significance of the process? • Name the stages. • What happens during each stage? • What is the difference between plant and animal cell?
  4. 4. MITOSIS VIDEO
  5. 5. MITOSIS & MEIOSIS ACTIVITY • Arrange the cards in the correct sequence
  6. 6. HOTS : Please explain what has this got to do with cell division? Planaria
  7. 7. SET INDUCTION Meiosis+-+The+Continuation+of+Life-SD
  8. 8. Meiosis • What does this picture tell us about meiosis? • How is the purpose of meiosis different from the purpose of mitosis?
  9. 9. Where does meiosis occur in a male and a female human? Inside testes in a male and ovaries in a female.
  10. 10. Meiosis in Plant Occurs in the • ovary (female) Ovary Occurs in the • anther (male) Anther
  11. 11. Meiosis produces reproductive cells (gametes) Sperm & Ovum Pollen grains & Egg cells Meiosis is the process of nuclear division that reduces the number of chromosomes in new cells to half the number of chromosomes in the parent cell.
  12. 12. Significance of meiosis: • Reduce chromosome number from diploid (2n) to haploid (n). • Promote genetic diversity (variation). Unique phenotypes may give a reproductive advantage to some organisms.
  13. 13. Which process restores the diploid number of chromosomes?
  14. 14. Meiosis reduces the chromosome number; Fertilisation restores the diploid number. egg sperm meiosis 46 fertilisation 23 23 46 23 46 23
  15. 15. Features of Meiosis Meiosis includes two rounds of division – meiosis I and meiosis II. Meiosis I Meiosis II Prophase I Prophase II Metaphase I Metaphase II Anaphase I Anaphase II Telophase I Telophase II Short interphase Haploid cells
  16. 16. During meiosis I, homologous chromosomes separate. 2n n During meiosis II, sister chromatids separate. n n [just like mitosis] How is the HAPLOID condition achieved? Chromosomes replicate ONCE but divide TWICE
  17. 17. Meiosis I: Reduction Division Nucleus Spindle fibers Nuclear envelope Early Prophase I (Chromosome number doubled) Late Prophase I Metaphase I Anaphase I Telophase I (diploid)
  18. 18. Prophase I Prophase I may last a long time. Human males:  about 1 week for prophase I  1 month for entire meiotic cycle Human females:  prophase I begins before birth, and ends up to decades later during the monthly ovarian cycle
  19. 19. Prophase I Interphase Prophase I (Bivalents)
  20. 20. Tetrads Form in Prophase I (each with sister chromatids) Homologous chromosomes join to form a TETRAD Synapsis
  21. 21. Crossing over: genetic recombination between non-sister chromatids Plural (chiasmata) - sites of crossing over
  22. 22. Crossing-Over Crossing over produces variation in gametes
  23. 23. Prophase I Early prophase Homologous chromosomes pair up - synapsis. Crossing over occurs. Late prophase Chromosomes short & thick. Spindle fibre forms. Nuclear membrane & nucleolus fragments. Centrioles move to opposite poles, aster forms
  24. 24. The longer the chromosome, the more chiasmata that can form
  25. 25. PROPHASE I
  26. 26. Metaphase I Homologous pairs of chromosomes align along the equator of the cell
  27. 27. METAPHASE I
  28. 28. Anaphase I Homologous pair saparate and move to opposite poles. Sister chromatids remain attached at their centromeres.
  29. 29. ANAPHASE I
  30. 30. Telophase I Nuclear membrane & nucleolus reappear. Spindle fibres disappears. Cytokinesis divides cell into two. 2 Daughter cells = n (haploid)
  31. 31. TELOPHASE I
  32. 32. MEIOSIS I
  33. 33. Meiosis I:  chromosome number has been cut in half  end result: 2 haploid cells Meiosis II:  Similar to mitosis  DNA does not replicate
  34. 34. Meiosis II: Prophase II Metaphase II Anaphase II Telophase II 4 Identical haploid cells Meiosis II is similar to mitosis
  35. 35. Prophase II Nuclear membrane & nucleolus fragments. Spindle fibres forms. Centrioles move to opposite poles.
  36. 36. PROPHASE II
  37. 37. Metaphase II Chromosomes align along equator of cell.
  38. 38. METAPHASE II
  39. 39. Anaphase II Sister chromatids separate and move to opposite poles. Equator Pole
  40. 40. ANAPHASE II
  41. 41. Telophase II Nuclear membrane & nucleolus reappears. Chromosomes become long & thin (decondense). Spindle fibre disappears. Cytokinesis divides cell into two. 4 haploid (n) daughter cells
  42. 42. TELOPHASE II
  43. 43. MEIOSIS II
  44. 44. Results of Meiosis Gametes (egg & sperm) form Four haploid cells with one copy of each chromosome
  45. 45. Centromere remains intact Anaphase I is the reduction division.
  46. 46. Meiosis II No interphase II (or very short - no more DNA replication) Remember: Meiosis II is similar to mitosis http://highered.mcgraw- hill.com/sites/0072495855/student_view0/c hapter3/animation__stages_of_meiosis.ht ml
  47. 47. What phase of meiosis?
  48. 48. Telophase I or Telophase II?
  49. 49. Which stage?
  50. 50. VIDEO How Meiosis Works
  51. 51. Genetic variation is almost infinite as a result of meiosis
  52. 52. HOTS Question: Name and describe TWO main advantages of meiosis relative to mitosis. (4) 1) Creates new combinations of genes which may result in the offspring being able to survive in a changing environment. 2) Halves the number of chromosomes so that after fertilisation, the diploid number is restored.
  53. 53. ACTIVITY • Show the sequence of Meiosis I and Meiosis II using plasticine on manila card. • Check your arrangement of mitosis/meiosis
  54. 54. Comparing Meiosis I and Meiosis II Activity
  55. 55. Comparing Mitosis and Meiosis Activity
  56. 56. VIDEO 2d Difference between mitosis and meiosis
  57. 57. The importance of meiotic cell division • Ensure the diploid number of chromosomes is maintained • Provides genetic variation
  58. 58. Appreciating the movement of chromosomes during mitosis and meiosis • Asexual reproduction (mitosis) produces offspring that are identical to the parent • Sexual reproduction produces genetic variation • If meiosis does not occur properly, the gametes formed will have abnormal number of chromosomes eg Down Syndrome & Klinefelter Syndrome (47 chromosomes) and Turner Syndrome (45 chromosomes).
  59. 59. Down Syndrome: A meiotic error Cause: Nondisjunction during either: anaphase I anaphase II
  60. 60. anaphase I anaphase II Homologous chromosomes fail to separate Sister chromatids fail to separate
  61. 61. Down Syndrome: trisomy 21 • In humans, if both chromosome 21 homologues go to the same pole, and the resulting egg is fertilised, it will be trisomic for chromosome 21. Egg cell Sperm cell n + 1 n (normal) Zygote 2n + 1
  62. 62. DOWN SYNDROME KARYOTYPE
  63. 63. The chance of having a Down syndrome child goes up with maternal age
  64. 64. Egg is in center of picture Many cumulus cells from the ovary are seen around the egg. This is a low quality, oocyte from a woman 41 years old. Egg is irregularly shaped and dark. A "good" egg from a 32 year old woman. Photos from Advanced Fertility Clinic in Chicago
  65. 65. Question: The diagram below represents the karyotype of a human. a) Why does the structure shown in Figure 2 have an X-shaped form? (2) Two sister chromatids are joined at the centromere.
  66. 66. Diagrams A, B and C below show the same stage in mitosis, meiosis I and meiosis II in a plant cell. a)Identify the stage shown giving your reason. Metaphase – chromosomes aligned at equator. Question:
  67. 67. b) The cell in diagram A has 20 units of DNA. How many units of DNA would there be in a cell from this plant at the end of: Cell A has 8 chromatids = 20 units. At end of mitosis, 4 chromosomes present. So = 10 units ii) meiosis? 2n for Cell A is 4 chromosomes = 10 units. At end of meiosis, 2 chromosomes present. So = 5 units ii) mitosis?
  68. 68. Question: The simplified diagram below shows a nucleus from a cell of an insect. a) Draw diagrams to show the two nuclei which would be formed if the cell would divide by mitosis. (2)
  69. 69. b) Draw diagrams to show three different nuclei which could be formed if the cell divided by meiosis. (Assume that no crossing over has taken place). (3) Any 3 from:
  70. 70. THE END
  71. 71. Genetic Variation in meiosis occurs in three ways: 1. Crossing over: prophase I 2. Random orientation of bivalents: metaphase I 3. Random orientation of sister chromatids : metaphase II
  72. 72. Crossing over does not create new alleles, it simply recombines existing ones in new ways. Meiosis I Meiosis II NEW COMBINATIONS 1. Crossing Over
  73. 73. 2. Random orientation of bivalents No. of different combinations: 2n 2n = 4 n = 2 No. of combinations: 22 = 4
  74. 74. Suggest explanations for the following observation. Meiosis, unlike mitosis, is not considered to form part of a cell cycle. (2) When cells divide by mitosis, cytokinesis and interphase follow and then the same phases are repeated. However, a cell divides by meiosis only once. There is no repetition of phases. Question:
  75. 75. 106 Gametogenesis Oogenesis or Spermatogenesis
  76. 76. 107 Spermatogenesis Occurs in the testes Two divisions produce 4 spermatids Spermatids mature into sperm Men produce about 250,000,000 sperm per day
  77. 77. 108 Spermatogenesis in the Testes Spermatid
  78. 78. 109
  79. 79. 110 Oogenesis Occurs in the ovaries Two divisions produce 3 polar bodies that die and 1 egg Polar bodies die because of unequal division of cytoplasm Immature egg called oocyte Starting at puberty, one oocyte matures into an ovum (egg) every 28 days
  80. 80. 111 Oogenesis in the Ovaries
  81. 81. 112 Oogenesis Oogonium (diploid) Mitosis Primary oocyte (diploid) Meiosis I Secondary oocyte (haploid) Meiosis II (if fertilization occurs) First polar body may divide (haploid) Polar bodies die Ovum (egg) Second polar body (haploid) a A X X a X A X a X a X Mature egg A X A X
  82. 82. Question: Read the passage below and insert the appropriate terms from the table below in the blank spaces provided. Note that each term in the table may be used once, more than once or not at all. Fertilisation Two Crossing-over Four Forty-six Genetic variation Haploid Homologous Chromatids Eight Gametes Diploid Twenty-three Chromosomes Nucleus Meiosis is an important biological process that reduces the chromosome number by half during the formation of …………… in animals. During the first meiotic "reduction division," the chromosomal pairs are partitioned so that each gamete contains one of each chromosomal pair that is it becomes ………… . gametes haploid
  83. 83. When haploid gametes unite during ……………… the resulting zygote is ………… having received one chromosome of each pair from each parent. Meiosis involves ……… successive nuclear divisions that produce …… haploid daughter cells. The first division (meiosis I) is the reduction division; the second division (meiosis II) separates the ……………….. . Meiosis increases ……………………… in the population. Each diploid cell undergoing meiosis can produce 2n different chromosomal combinations, where n is the haploid number. fertilisation diploid two four chromatids genetic variation

×