1. MITOSIS & MEIOSIS

2. Why can’t a cell keep on increasing
in size?
Cells MUST divide when their SA:V becomes small.

3. Cells divide :
1.For growth
2. To produce
gametes or spores
3.To replace
damaged cells
Salmon gametes mixing
Mucor

4. The nucleus contains thread-
like structures called:

5. A nucleus can contain:

6. TWO types of cells in the body
Non-reproductive Gametes
or somatic cells (sex cells)
diploid number haploid number
of chromosomes
sperms
phagocyte Nerve cell

7. types of cell division
produces body cells
produces sex cells

8. takes place in any part of a plant or animal
which is producing new cells for growth or
replacement
e.g.
bone marrow producing new blood cells

9. e.g.
bone marrow producing new blood
cells

10. e.g.
skin cell production
growth of a muscle

11. Mitosis in
buds
Mitosis in
shoot & root
tips

14. occurs in reproductive organs and results
in the formation of sex cells
Meiosis forms the
ovum and sperms
in animals.

15. Key Haploid gametes (23)
Haploid Where does
Egg (23)
Diploid meiosis occur
in a male and a
female human?
Sperm (23)
MEIOSIS FERTILISATION
Ovary Testis
Diploid
zygote
(46)
Mitosis and
Testes in
development males &
Multicellular diploid ovaries in
adults (46)
females

16. MALE FEMALE
Sex organs Testes Ovaries
Gametes Sperm Ovum / egg

17. MALE FEMALE
Sex organs Anthers Ovaries
Gametes Inside pollen Egg cell
grains

18. Mark with an ‘X’ where meiosis occurs.

20. is called a REDUCTION-DIVISION.
Why?
as it causes the chromosome number to
halve
How is it possible to produce 4
cells by meiosis?

22. Mitosis or meiosis?

23. Which process restores the diploid
number of chromosomes?

24. Meiosis reduces the chromosome number;
Fertilisation restores the diploid number.
23 23
46 46
meiosis egg
23
23 fertilisation
46
sperm

25. Both occur in plants and animals.
Both produce new cells as they
are types of cell division.

27. TWO daughter cells

30. First
division
Second
division
FOUR daughter cells

31. Genetic
variation is
almost infinite
as a result of
meiosis

33. First
division
Second
division
NEW COMBINATIONS

34. 1. exchange of genetic material during
meiosis
2. random fertilisation

35. Random Fertilisation
= even more variation
 A human ovum plus a human sperm
- 1 of 8 million combinations possible for
each ovum and sperm
- 223 x 223 = over 70 trillion combinations
 Any 2 parents will produce a
zygote with over 70 trillion
possible combinations without
considering crossing over
UNIQUE!!

36. Mitosis Meiosis
1) Two cells are produced Four cells are produced
2) Cells have the diploid Cells have the haploid
number of chromosomes number of chromosomes
3) One division occurs Two divisions occur
4) Cells are genetically Cells are genetically
identical (CLONES)
CLONES different
5) Produces somatic cells Produces sex cells

37. 46
Write the
23 23
numbers of
chromosomes
found in the
cells shown. 46
46

38. are thread-like structures found in the nucleus
they only show up clearly at cell division as
they shorten and thicken

39. Number of Chromosomes
Fruit Flies: 8 Carrots: 20
Dog: 48
Shrimp: 254 Adders tongue
(Fern): 1260
Largest number of
chromosomes

40. Fig. 4 Homologous
chromosomes of a fruit fly.

41. 46
chromosomes
in humans
44 autosomes
2 sex chromosomes

43. Down’s Syndrome children have
47 chromosomes

44. The chance of having a Down syndrome child
goes up with maternal age

45. A "good" egg from a
Egg is in center of picture 32 year old woman.
This is a low quality, egg
from a woman 41 years old.
Egg is irregularly shaped
and dark.

46. A chromosome consists of DNA
packed around proteins

47. The total extended length of DNA in a
human cell is nearly 2m.
Cheek cells

48. Carry information
to make an
individual

50. consists of two parallel strands linked
together by weak hydrogen bonds
it is twisted into a spiral

51. is a DOUBLE HELIX (a helix is any spiral-
shaped object)

52. four different bases:
A: adenine;
T: thymine;
C: cytosine;
G: guanine

53. A always pairs with T
C with G
this is called
complementary base
pairing

54. is the basic unit
of DNA

55. The diagram shows
part of a DNA
molecule.
Complete the
diagram by labelling
the bases.
T
G
G
A

56. is a series of chemical structures called
bases along the length of a chromosome
provides ‘instructions’ to the cell, e.g. to
make pepsin or the skin colour

57. is a spontaneous change in a gene or a
chromosome which may produce a change in
the characteristic under its control
a mutation can be:
 harmful
 lethal
 beneficial (mutations in bacteria often
produce resistance to drugs)

58. Naturally
 when chemicals on the DNA change position
during nuclear division
Artificially
 by means of mutagens

59.  an agent that causes a change in
genetic composition

60. X-rays
UV-rays

61. cigarette smoke
asbestos

62. formaldehyde
pesticides

63. Question: MAY, 2004 (pg 78)
It is not advisable for pregnant females to take X-
rays because these can cause mutations in the
developing foetus. The X-rays can in fact act as a
mutagen (or mutagenic agent).
ii)Explain the term mutation by referring to the
DNA molecule. (2)
A spontaneous change in the structure of DNA.
A change in the sequence of bases occurs.

64. Question: pg 78
ii) Name one human disease or condition which
results from a mutation. (1)
Haemophilia / Down’s syndrome
iii)Name one mutagen other than X-rays. (1)
UV rays

65. the
information
to build
proteins

66. What are the building blocks of
proteins called?

67. Name the bond between amino
acids.

68. Fig.9 Protein synthesis inside a cell.

69. Fig.9 Protein synthesis inside a cell.

70. THE END