1. While the DNA between individuals is nearly identical, small variations exist in 0.1% of the DNA that differs between people. 2. These variations arise from both genetic and environmental factors and lead to differences in traits between individuals of the same species. 3. Genetic variations come from mutations, sexual reproduction through processes like independent assortment and crossing over during meiosis, and random fertilization leading to offspring that are highly varied.

1. The same but
different !
Variation

2. AREN’T GOD’S CREATIONS AMAZING?

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4. The DNA Between Individuals is Identical.
All differences are in the 0.1% of DNA that varies.
A
C
C
G
T
C
C
A
G
G
A
C
C
G
T
G
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A
G
G
It’s hard to
believe sometimes!

5. Why aren’t fruits from the
same plant identical ?

6. So why are Identical twins
not identical ?
 Twins have
identical genes in
their bodies…….
 Yet they do not
have identical
characteristics.

7. What is a species?
 A group of organisms which can
reproduce
 Examples?
 The differences within a species
are called variation
Variation is difference in traits in
organisms of the same species

8. VARIATION

11. Variation In Humans
Unattached
ear lobes are
inherited as a
dominant
trait.
Attached ear
lobes are
inherited as a
recessive
trait.

12. Variation In Humans
 Having a bent little finger is a
dominant trait

14. Variation In Humans

15. Skin colour

18. You got half of your chromosomes from
your mum and half from your dad
Who did you
inherit you eye
colour from?
Nose shape?
Hair colour?
Where did you get your chromosomes from?Where did you get your chromosomes from?

19. Cause of Variation
1. Genes (inherited)
2. Environment.
3. Interaction between genes and the
environment.
Examples?

21. Environmental or Inherited?

22. Variation
Differences in characteristics shown by
organisms of the same species
 two types of variation:
DISCONTINUOUS CONTINUOUS

23. Discontinuous Variation
 Produces:
individuals with clear-cut differences with no
intermediates between them
 examples:
 blood group in humans
 sex
 tongue rolling
Either
OR
traits
Either
OR
traits

24. Eye colour in 9K
0
1
2
3
4
5
6
7
8
blue green hazel brown grey black
Frequency
DISCRETE
DISTRIBUTION
Discontinuous Variation

25. The environment cannot change discontinuous
type of variations
No matter how much you stay in the sun orNo matter how much you stay in the sun or
what you eat – will not change your bloodwhat you eat – will not change your blood
group!!group!!

26. Continuous Variation
characteristic varies amongst the members
of a species in a smooth continuous way
from one extreme to the other

27. Continuous variation is affected by:
1.many genes
2.AND the environment

28. The environment CAN change these variations
Sun bathing causes
tanning of skin.
Eating carrots makes
human skin and feathers
in birds turn orange.

29. Continuous Variation:
 Examples:
 Mass
 Height
 Intelligence
 Colour of organs & organisms

30. human height
continuous
variation
No.ofindividuals
NORMAL
DISTRIBUTION
Continuous Variation

31. Differences between Continuous & Discontinuous Variation
Continuous Discontinuos
Is controlled by many pairs
of alleles
Is controlled by a single pair
of alleles
Caused by genetic /
environmental factors or
both. (only genetic factors
inherited)
Caused by genetic factors
only
Normal distribution Discrete distribution
Eg. Height, skin colour,
Intelligence, body weight.
Eg. Blood group, ability to
roll tongue, fingerprint,
colour blindness.
Eye colour in 9K
0
1
2
3
4
5
6
7
8
blue green hazel brown grey black
Frequency

32. How does variation come about?
#Environmental factor
#Genetic factor
 Sexual reproduction
 Mutations

33. Genetic Factor that cause variation
GENETIC
MUTATION
SEXUAL
REPRODUCTION
CHROMOSOMAL MUTATION GENE MUTATION
INDEPENDENT
ASSORTMENT
CROSSING
OVER
RANDOM
FERTILISATION
duplication
inversion
translocation
deletion
deletion
insertion
substitution

34.  Offspring of sexual reproduction
are highly varied
The Origins of Genetic Variation
Sexual Reproduction

35. What about this wheat grown
in the same field from the
same parent plants ?

36. Genetic Factor that cause variation
GENETIC
MUTATION
SEXUAL
REPRODUCTION
CHROMOSOMAL MUTATION GENE MUTATION
INDEPENDENT
ASSORTMENT
CROSSING
OVER
RANDOM
FERTILISATION
duplication
inversion
translocation
deletion
deletion
insertion
substitution

37. Crossing-over between chromatidsCrossing-over between chromatids
during meiosis 1 (Prophase 1)during meiosis 1 (Prophase 1)
Based on: Mader, S., Inquiry Into Life, McGraw-Hill

38. Crossing Over
– Homologous
chromosomes
exchange
genetic
information
during
Prophase I
meiosis
– Genetic
recombination
occurs
– more genetic
diversity to
gametes
Figure 8.18
Prophase I
of meiosis
Metaphase I
Metaphase II
Gametes
Recombinant chromosomes
Spindle
microtubules
Tetrad
Chiasma,
site of
crossing
Over (remain attached to
e/o at chiasmata until
Anaphase I)
Homologs are
closely paired

39. Genetic Factor that cause variation
GENETIC
MUTATION
SEXUAL
REPRODUCTION
CHROMOSOMAL MUTATION GENE MUTATION
INDEPENDENT
ASSORTMENT
CROSSING
OVER
RANDOM
FERTILISATION
duplication
inversion
translocation
deletion
deletion
insertion
substitution

40.  The orientation of the homologous pairs of
chromosomes (tetrads) at metaphase I is a matter
of chance, each has 2 possible ways they can line
up.
Independent Assortment of Chromosomes
Figure 8.17
Possibility 1
Metaphase
of
meiosis II
Combination a Combination b Combination c Combination d
Gametes
Possibility 2
Metaphase of
meiosis I
MEIOSIS

41. ……chromosomes can line upchromosomes can line up 222323
or 10 million (10or 10 million (1077
)) different waysdifferent ways
in meiosis Iin meiosis I
……so each person can produceso each person can produce
10 million (or 1010 million (or 1077
) different types) different types
of gametesof gametes
During meiosis in humans…During meiosis in humans…

42.  Meiosis
– homologous chromosomes separate
independently from each other and pass
into a different gamete ( INDEPENDENT
ASSORTMENT).
– a great variety of gametes are produced
Causes of VariationsCauses of Variations

43. Genetic Factor that cause variation
GENETIC
MUTATION
SEXUAL
REPRODUCTION
CHROMOSOMAL MUTATION GENE MUTATION
INDEPENDENT
ASSORTMENT
CROSSING
OVER
RANDOM
FERTILISATION
duplication
inversion
translocation
deletion
deletion
insertion
substitution

44. For each couple…For each couple…
101077
types of spermtypes of sperm
xx
101077
types of eggstypes of eggs
10101414
types of childrentypes of children

45. ~~ENDEND~~
END OF PART 1
GO TO 6.2

46. EXTRA

47. Question: SEP, 2005 [pg. 83]
Look at the drawings of the two men.
List two features shown in the diagram, that are
inherited and three features that are not inherited. (5)

48. Types of VariationsTypes of Variations
 2.Discontinuous Variation
– the characteris clear-cut & not showing
intermediates
– eg. tongue rolling, earlobes and colourof corn
albinism
Eye colour in 9K
0
1
2
3
4
5
6
7
8
blue green hazel brown grey black
Frequency
DISCRETE
DISTRIBUTION

50. Environmental variations cannot be
inherited

52. XXY males

Tall

High testosterone

Severe acne

More predisposed to
criminal activities and
behavioural problems

53. Poliploidy

Chromosomal Mutation

Polyploid organisms:
− Triploids (3n) – three sets of chromosomes
of one type
− Tetraploid (4n) – have four sets of
chromosomes

Polyploidy is common in flowering
plants

Not occuring in animals

Produce bigger fruit with more

54. Duplication
a
b
c
d
e
f
g
a
b
c
d
e
d
e
f
g
Occurs when a broken
segment of a
chromosomes joins with
the other chromosomes
of the homologous pair

55. a
b
c
d
e
f
g
a
b
c
d
e
f
g
a
b
c
d
e
f
g
a
b
c
d
e
q
r
a
b
c
d
e
f
g
a
b
c
d
e
f
g
l
m
n
o
p
q
r
a
b
c
d
e
f
g
a
b
c
d
e
f
g
l
m
n
o
p
f
g
Translocation
Occurs when a segment of a chromosome
breaks off and joins a non homologous
chromosomes

56. a
b
c
d
e
f
g
a
b
c
d
f
g
Deletion
Occurs when one end of a chromosome
or an internal segment breaks off
the two rejoin to form a chromosome defecient
gene

57. a
b
c
d
e
f
g
a
b
c
d
f
e
g
Break
Inversion
Occurs when a segment
of a chromosome breaks
loose, rotates 180 and
rejoin in reverse direction
- lead to altered gene
activity