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
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
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
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.
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
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