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Sandra Sou HSC notes 2017/2018

9
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Evidence of evolution suggests that the mechanisms of inheritance, accompanied by selection,
allow change over many generations
...

Changes in
chemical
conditions in the
environment
...


-

-

-

-

Evolution is the change in living organisms over many generations
Evidence suggests that change in the environment is a driving force behind change in living
organisms
...

As a result of environmental change, resources may become limited and so living organisms
will begin to compete for the available resources in order to survive
...

Change in the environment of a population influences evolution because it results in selective
pressure acting on organisms
...

That is, individuals that compete successfully in the new environment outlive those that do
not have such variations
...

It is important to remember that an individual does not develop an adaptation in response to
the environmental change – the organisms already possess the random variation that confers
an advantage under the new conditions
...


Environmental changes can be physical
 Include factors such as temperature, availability of water, light, wind, slope and tides
 Physical changes have been instrumental in the evolution of organic molecules from
inorganic substances on early Earth
...
Water-holding frog)
 The influence of fire, resulting in the survival of fire-resistant species in Australia (e
...
the
bottlebrush)
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Sandra Sou HSC notes 2017/2018
 The ancient kangaroo’s unspecialised teeth had to develop high crested molars to grind
the tougher vegetation
 Kangaroos were previously small and omnivorous but became larger
- England – Industrial Revolution
 In 19th century – the polluted environment led to dark sooty backgrounds for coloured
moths to camouflage against
 Light coloured pepper moths were easy to see and were eaten by birds before they could
reproduce
 Genes of dark-colouring were passed onto the next generation
 As pollution was reduced- lighter-coloured moths began to dominate as the gene for
dark-colouring was no longer favourable
-

-

-

-

-

Environmental changes can also be chemical
 The first life forms are believed to have lived in an anoxic (oxygen-free) environment and
some of these primitive life forms began to produce carbon dioxide as a result of their
metabolism
 Appearance of carbon dioxide in environment led to emergence of photosynthetic
organisms – used carbon dioxide in their metabolism and produced oxygen as a byproduct
 Increasing oxygen levels in the environment led to the evolution of organisms that were
aerobic – organisms that could use oxygen in their respiratory pathway
...

E
...
Mosquitoes and DDT
 When DDT was first used as an insecticide to kill malarial mosquitos, low concentrations
were effective
 In subsequent doses, higher concentrations were needed and the sprayings became less
effective
 The few DDT-resistant mosquitoes that had survived passed on their genes to their
offspring, and now the mosquito population is mainly resistant
E
...
Increase in soil salinity
 Plants that tolerate salinity survive (saltbush)
 Such plants dominate over less salt-tolerant species
E
...
Rabbits and myxomatosis
 In 1950, the myxoma virus was introduced to attempt to control rabbit numbers (they
were a problem since 1859)
 Virus carried by fleas or mosquitoes – causes disease myxomatosis in rabbits
 In the first few years, 99% of infected rabbits died
 Then death rate fell to 95% in 1953 and 50% in 1960
 Survivors from the first infections passed on genes of resistance
 Rabbits resistant to myxoma virus increased in number
As a result of environmental change, resources may become limited and so living organisms
will begin to compete for the available resources in order to survive
...

- Native species can become endangered or extinct (or restricted to some islands) due to
competition with introduced species for food, access to water and nesting or burrowing sites
...

 avoid direct competition
 different species may be produced
 fruit flies have developed different species – each confined to a different type of tree
 different flowering and fruit times result in different breeding cycles


–

–
–
–
–

Describe, using
specific
examples, how
the theory of
evolution is
supported by the
following areas
of study:
Palaeontology,
including fossils
that have been
considered as
transitional
forms
...

Comparative
embryology
...

Biochemistry
...
g
...

 These fins are thought to represent the ancestral limbs of terrestrial vertebrates
 It is a living fossil
 FISH features: scales, fins, gills
 AMPHIBIAN features: lobe-fins, lungs
 E
...
Reptiles to birds: Archaeopteryx
 Small flying dinosaur with feathers
 Appeared in the late Jurassic (found in rocks dated 150mya)
 Has clear impressions in limestones of feathers on its forelimbs and on its tail, as well
as a wishbone extending into a keel bone for attachment of flight muscles – typical of
birds
 Also displays typical features of a reptile, such as teeth in its beak, bones in its tail
and claws on three digits of its forelimbs (wings)
 E
...
Plants: Seed ferns
 Extinct seed ferns appear to be ancestors of present-day gymnosperms (conifers)
 Seed ferns look like ferns but naked seeds can be seen attached to their leaves
 Evidence suggests that their life history was similar to that of gymnosperms
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Sandra Sou HSC notes 2017/2018
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Biogeography:
 Study of the geographical distribution of organisms, both living and extinct
 Darwin-Wallace theory of evolution proposes that, for a new species to arise, a group of
individuals must become isolated from the rest
 “A new species is one where the individuals cannot produce fertile offspring if they are
mated with individuals of a pre-existing species”
 Basic principle is that each plant and animal species originated only once
 This is called the centre of origin (or the common ancestor)
 Regions that have separated from the rest of the world, e
...
, Australia and NZ, often have
organisms that are distinctive and found nowhere else (endemic)
 General principles of dispersal and distribution of land animals:
 Closely related organisms in different geographical areas probably had no barrier to
dispersal in the past
 The most effective barrier to distribution is the oceans and seas
 By looking at the pattern of distribution today plus its fossil distribution in the past,
we are able to reconstruct its evolutionary history
 Prediction:
 If isolation is a criterion necessary for new species to arise from an original species,
the new species should resemble species with which they shared a habitat
 Evidence:
 During his travels, Darwin studied and compared numerous animals (including his
now famous finches) on islands such as the Galapagos
 Alfred Wallace noted that the north-western Indonesian islands, including Bali, had
bird species most similar to those of the closer Asian mainland, whereas islands in
the south-east including Lombok, had birds that were most similar to those in nearby
Australia
 Nothing how close Bali and Lombok are, it is easy to understand how this led to his
conclusion that the island forms may have evolved from mainland forms which
became isolated
 Typical examples where biogeography supports macro-evolution is that of the
flightless birds (ratites) and continental drift
 For Example - Waratahs
 3 genera of waratahs; distribution spans southern pacific ocean
 The present-day distributions of these closely related species in the eastern parts of
Aus, and New Guinea and the Western part of South America suggest that the 2
regions may have been connected in the past
Comparative Embryology:
 The embryos of different vertebrates are very similar
 The embryos of many different vertebrates all have gill pouches at some stage of
development
...


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Sandra Sou HSC notes 2017/2018
 Haeckel’s embryos are a famous illustration comparing the early stages of various
animals
...


-

Comparative Anatomy:
 Comparative anatomy is the study of the differences and similarities in structure
between different organisms
...

 E
...
Pentadactyl Limb
 The pentadactyl limb is a 5-digit limb
 It is a structure of bones that is found in many
vertebrates
 It is believed that this limb was inherited from an
aquatic ancestor – lobe-finned fish
 E
...
Xylem
 Xylem is found in almost all plants
...


-

Biochemistry:
 All organisms share the same basic biochemistry
...

 DNA Hybridisation
o Two strands of DNA from different species are separated using heat
o The single strands from each species are mixed with other species
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Sandra Sou HSC notes 2017/2018
o







Explain how
Darwin/Wallace’s
theory of
evolution by
natural selection
and isolation
accounts for
divergent
evolution and
convergent
evolution
...
However, not all pairs
will match
o The degree of pairing determines closeness
o Species that diverged recently from their ancestor are expected to show a high
degree of hybridisation
DNA Sequencing
o DNA sequencing is the analysis of precise sequences of nucleotides in a DNA sample
o This process has allowed mapping of whole genetic makeups, leading the mapping of
the human genome
Comparative DNA Sequencing
o This involves comparing the sequences to sequences from other species
o This is done

According to Darwin/Wallace, evolution occurs by a process of natural selection in the
following steps:
1
...

2
...

3
...

4
...

The Role of Isolation:
 For a new species to evolve, groups of organisms need to become isolated from each
other
 Usually the organisms become separated by a physical barrier
 Within each separate population, different mutations occur, and therefore, different
variations are produced
 Natural selection acts differently on each isolated population, as there are different
environmental conditions and selection pressures
 Over time the populations differ so much that they no longer interbreed, and as such, a
new species was produced
 Isolation can be created by a difference in food preference, to the splitting of the
continents
...

 This process begins with a common ancestor that branched off to different species
 This is due to isolation – environment, food, resources, etc
...
This is evidence of
divergent evolution
...
g
...


Aim: To observe natural selection by means of a model
Requirements: Set of moth cards & die
Procedure:
1
...
Shuffle the cards to represent random mating and deal 15 pairs
3
...
Remove 15 cards per year (to demonstrate predation)
5
...


Case Study: Salt Bush
An increase in salinity due to multiple factors such as:
 A low water table
 Deforestation
 Irrigation
- The salt bush could tolerate salinity and survived
- The stems and leaves are covered with small white scales called scurf, that help the plant
conserve water
...

- The leaves are sharp spines alternately clustered around the stem of the plant
...




Perform a firsthand
investigation or
gather
information from
secondary
sources (including
photographs/
diagrams/models)
to observe,
analyse and
compare the
structure of a
range of
vertebrate
forelimbs
...


Molecular
Technology
Amino Acid
Sequencing

Description

Nature of Evidence



The nucleotide sequences making up genes
and chromosomes can be analysed and
compared
The most widely used technique is the
Edman degradation where special reagents
under alternating basic and acidic
conditions remove one amino acid at a time
from the protein’s N-terminus
...

The greater the similarity, the closer the
relationship between the organisms
...
The higher the temperature
required, the stronger the bonds holding
the hybrid molecules together and
therefore the more similar the base
sequence



Human serum (blood minus blood cells and
clotting agents) is injected into another
mammal, such as a rabbit
...

E
...
a comparison of
human and
chimpanzee’s amino
acid sequence of
Cytochrome C show
that the sequence is
exactly the same
...

Evolutionary
relationships are
established on the
basis of the relative
strength of the bonds
holding the hybrid DNA
molecules together
...

More precipitation
corresponds with a
closer relationship –
precipitation produced
by reaction with human
serum is taken as 100%
Studies with
immunisation show
that between humans
and chimpanzees,
there is 97%
precipitation
...

1831 –
1836




Much evidence was available for evolution but no plausible mechanism
...







Jean-Baptiste Lamarck first published his evolution theories
He suggested ‘The Inheritance of Acquired Characters’
I
...
organisms altered their behaviour in response to environmental change
...

For example, giraffes developed their elongated necks and front legs by
generations of browsing on high tree leaves
...








Charles Darwin travelled on a ship called ‘the Beagle’
...

He commented on how the organisms were very well suited to Australia’s
environment
...

Darwin knew what a huge impact his knowledge would make on the world
when he released it, so he withheld his theory for 25 years
...


1854 –
1862



Wallace visited Malaysia and observed species there
...

Papers by Wallace and Darwin were jointly presented
...

It was only when he felt the social and political climate was right, did he
publish his information
He chose to publish it during a time of great societal change; i
...
the Industrial
Revolution, and a time when the power of the Church was weaning
...

Cartoons were published in the media of Darwin’s head on the body of an ape,
mocking his theory of evolution
...
Great
debates were fought out by evolutionists and creationists (a famous one being
between Thomas Huxley and Bishop Samuel Wilberforce)
...

Darwin has been blamed for the destruction of religion and the rise of
atheism, fascism, communism and even the Second World War, as people like
Karl Marx base their philosophies on The Origin of Species
...


2
...

Students Learn to: Notes
-

Outline the
experiments
carried out by
Gregor
Mendel
...

This choice in plant was critical to his success as he could easily grow them in large numbers,
they produced new generations quickly and had easily distinguishable characteristics
...

He is known as the father of genetics
...

In 1866, he published results of his work in a paper called “Experiments in plant
hybridisation”, but it was ignored
...

He worked with pure breeding plants and then hybrids, studying the inheritance of one
particular trait at a time, including:
 seed form
 flower colour
 flower position
 seed colour
 stem length
 pod form
 pod colour
Both Darwin and Wallace were unaware of Mendel’s work at the time
...

However, Mendel did not seem to make any links between his work and that of Darwin
...
He did
this by enclosing male and female parts within
the same flower
...
He did this
by manually transferring pollen between the two
plants
...

 These offspring are termed hybrids, but they
resemble only one parent
...

- Then crossed their off-spring (monohybrid cross)
 He crossed two hybrid plants from the first filial generation (F1) of the previous
experiment
...

That is, the average ratio observed in offspring is 3:1
...

 Mendel’s conclusions about organisms that he made his results are summed up in his
Law of Segregation:
 An organism’s characteristics are determined by ‘factors’ (we call them genes), that
occur in pairs
...

 During fertilisation, the factors pair up again; they don’t blend, but match up with
each other
 Mendel also observed that one ‘factor’ is dominant over the other; they don’t
blend
...

- Mendel made direct counts of the resulting offspring, giving quantitative data, which he
collated and analysed to identify patterns and trends
...

- He used a mathematical model to explain the phenomenon of inheritance and to make
predictions for future crosses (which he later tested successfully)
...

- Over the period of 2 years, Mendel established pure breeding lines from pea plants which
he then crossbred to study the inheritance
- When Mendel experimentally tested this hypothesis, he obtained quite different and
unexpected results – all of the initial offspring resembled one parent, but in later
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Sandra Sou HSC notes 2017/2018
generations the other parent’s trait would arise, appearing in later generations the other
parent’s traits would arise

Variation by Environment or Inheritance?
 Both inheritance and the environment determine the characteristics passed through
generations
 An animal may be small and thin as it couldn’t find food
 A tree might have bent branches based on the wind
 These are both environmental influence that can change throughout an organism’s life
 However, there are characteristics like eye colour and tongue-rolling that are genetic
 This is randomly determined during meiosis

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Sandra Sou HSC notes 2017/2018
- Describe the
Accuracy
aspects of the
Quantitative data –
experimental
Mendel counted and
techniques
meticulously recorded
used by
exact numbers of
Mendel that
plants with each
led to his
characteristic
...

Careful records –
Mendel meticulously
recorded his data
...

Large sample sizes
– Mendel used
thousands of
plants for each
genetic cross to
be trialled
...

Pure-breeding plants – Mendel did this by
ensuring self-pollination (bags over plants) for
many generations over a period of two years
...

Use of garden peas – Garden peas produced
new generations quickly and had easily
distinguishable characteristics
...


-

-

-

- Distinguish

between
homozygous
and
heterozygous
genotypes in
monohybrid
crosses
...

A breeding experiment that looks at the inheritance of only one characteristic is known as a
monohybrid cross
The offspring of a cross are known as F1 or first filial generation
Mendel cross-bred tall and short plants, and all the offspring were tall
Parents: tall plants x short plants
F1: all tall
He then took these tall offspring and allowed them to self-fertilise, and obtained the
following results for the second filial generation (F2)
F1: tall x tall
F2: Both tall and short plants, nut more tall than short ones
In the F2 generation, most of the plants were tall but some were short
...
Mendel found the ratio of tall to short was approximately 3:1
This is known as the mono-hybrid ratio
He repeated these experiments testing all the characteristics he had used in garden peas
...
g
...
g
...

chromosome and control the same characteristic

- Explain the

relationship
between
dominant and
recessive
alleles and
phenotype
using
examples
...
g
...

 They are ALWAYS present in pairs in body cells
 If the two genes are the same allele, then the organism is said to be homozygous for
that characteristic
...

 In simple genetics, one of the alleles is DOMINANT, and one of them is RECESSIVE
 Taking a characteristic, e
...
Pea Plant height
...
T is the dominant tall allele, t is the recessive, short
allele
 A tall pea plant can be either TT or Tt, as the dominant gene is always expressed
 A short plant is always tt

Outline the
reasons why

the
importance of
Mendel’s
work was not
recognised
until some

time after it
was
published
...
He presented his papers to a very small group of scientists (about 40)
at two meetings in 1865 of The Natural Science Society of Britain – a fairly low profile
gathering in the province of Moravia
...
Very little was known
about cells; chromosomes, mitosis and meiosis were unknown and the studies of genetics
did not exist
...
Mendel’s use of
mathematics and statistics was different to the norm in biology at that time
...
Darwin
published On the Origin of Species in 1859
...

 Mendel’s work has been widely acknowledged and valued since then
...

-

Pedigrees are family trees
...

Patterns to recognise characteristics are
inherited:
 If two non-affected parents have an
affected child, then the trait is a
recessive one
...

In general, squares denote males and circles denote females
...


 Solve



problems
involving
monohybrid
crosses using
Punnett
squares or
other
appropriate
techniques
...


Hybridisation
Jersey-Sahiwal – Jersey cattle and the African
Sahiwal cattle in Kenya

Purpose



To increase milk yield and quality
...


Labradoodle – cross between Labrador and
poodle (within the species of dog)



does not shed hair – important for people
with asthma or allergies
no body odour
do not need constant bathing and brushing
easy to train
can be trained as guide dogs
drought tolerance
resistance to sun
resistance to disease
good milling and baking qualities
late maturing

Yandilla Wheat – Indian Wheat and Canadian
Fife Wheat











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Sandra Sou HSC notes 2017/2018
3
...

Students Learn to: Notes
–

Outline the
roles of Sutton
and Boveri in
identifying the
importance of
chromosomes

–
–
–
–
–
–



–

Walter Sutton
He was an American geneticist who studied meiosis of cells of grasshoppers
In 1902, he proposed the Chromosomal Theory of Inheritance
Suggested Mendel’s inheritance “factors” are carried on chromosomes
Formulated theory after observing meiosis in grasshopper testicles
Sutton’s observations revealed that:
 Chromosomes occur in distinct pairs as distinct entities, visible during meiosis in grasshopper
cells
...

o These chromosomes in each pair have the same size and shape
...

o The chromosomes in each pair separate
...

 Fertilisation restores the full number of chromosomes in the zygote
...

 Chromosomes are units involved in inheritance
...

 If two characteristics are on the same chromosome (linked genes) they will move together
rather than separately according to Mendel’s law of independent assortment
...
He studied the
behaviour of the cell nucleus and chromosomes during meiosis and after fertilisation
...

 When a normal egg and sperm fused, the resulting offspring showed characteristics of
both parents
...

o When an egg with its nucleus removed was fertilised with a sperm, the resulting
sea urchin larvae showed characteristics similar the male parent
...

 Boveri deduced that:
 A complete set of chromosomes (in pairs) is required for normal development
...

 There are more hereditary “factors” than chromosomes and so there must be many
factors (today known as genes) on one chromosome
...
They deduced that chromosomes
are hereditary units and occur in pairs
Before Sutton and Boveri’s work

After Sutton and Boveri’s work

Where in the cell are heredity
factors found?

Cytoplasm and nucleus

Nucleus only

What material stores the heredity
information?

Unsure – perhaps proteins?

How are inherited factors passed
to the next generation?

Gametes transport “factors”, but
how or what these factors were
was unknown

A full set of paired chromosomes,
where many heredity factors are
carried on each chromosome
Random assortment during
meiosis – units of inheritance
carried on chromosomes in
gametes

Nature of chromosomes

Chromosomes were believed to
disappear and reappear and were
all believed to the same size and
shape

Chromosomes occur in set
numbers in every cell in pairs and
each pair of chromosomes has
the same size and shape

– Describe the

–
–
–
–
–

Each chromosome is made up of about 60% protein and 40% DNA
The DNA is coiled tightly around a protein core (histone proteins)
A gene is a section of DNA on a chromosome
It is made up of a particular sequence of bases
Different genes are different lengths

– Identify that

–

DNA (deoxyribonucleic acid):
 In 1953, Watson and Crick described the DNA molecule as a double stranded helix
 A DNA molecule is made up of two chains or strands of small building blocks or monomers
called nucleotides
...


chemical
nature of
chromosomes
and genes
...


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Sandra Sou HSC notes 2017/2018
Inheritance of genes
– Explain the
Factors (genes) responsible for heredity occur in pairs
...

structure and
behaviour of
Only one of each pair of genes is present in each gamete;
chromosomes
the number of genes in gametes is half that of body cells
...

and the
Four haploid cells are formed in meiosis
...

Genes may change position during meiosis, leading to
increased variation: recombinant types can be produced
...

Alleles for a particular characteristic are located on each
member of a homologous pair, which segregate during
meiosis
...

Meiosis involves two divisions, hence forming four daughter
cells
...

Crossing over may occur when two chromosomes swap
chromatid parts
...


–

Describe the
inheritance of
sex-linked
genes, and
alleles that
exhibit codominance and
explain why
these do not
produce simple
Mendelian
ratios
...
They can line up in the middle of the cell in many different ways
...
The combinations of alleles of the gametes will vary
across cells and differ from the parent
RANDOM FERTILISATION: When the male and the female mate, the two different gametes
randomly fuse
...


Sex linkage:
SEX is a genetically determined characteristic
Every cell in the human body contains 23 pairs of chromosomes 22 pairs of autosomes (general
traits within the body) and 1 pair of sex chromosomes (the 23rd pair)
Sex chromosomes may differ from each other in size and shape
For females, both the sex chromosomes are the same
...
Females
have two X chromosomes, and the chromosomes are homozygous
For males, the sex chromosomes are different
...
The Y chromosome is
shorter than the X chromosome
...

Most sex-linked characteristics are recessive
 Take, eg, haemophilia
...

 Females:
o A normal female’s genotype – XHXH
o A carrier female has the genotype - XHXh
o A haemophiliac female has the genotype – XhXh
 Males:
o A normal male - XHY
o A haemophiliac male - XhY
As you can see for the example, males only have to inherit a single gene to have the
characteristic
...

Sex Determination
The offspring of most animals have an equal chance of being male or female
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Sandra Sou HSC notes 2017/2018
 This is determined by the following mechanisms during the life cycle
 The segregation of sex chromosomes during meiosis
 The transfer of one sex chromosome to each gamete
 The fusion of gamete during fertilisation
– Co-Dominance:
 In this case, the two alleles are not dominant over each other
 Both alleles are expressed in each other’s presence
 There is no “blending”, the alleles do not mix, but simply, both can be seen
 An example is roan coloured cattle
 If a type of cattle has the gene for red, and white, it would not make a pink cow, but the hairs on
the cow would be both red AND white, making an interesting roan colour
...


–

–

–

–
–

Looking at the cross in the form of a Punnett square, we can see that a cross concerning a
codominant trait does not give the simple Mendelian ratio of 3:1
The cross between the two roan cows of the F1 generation does not give the 3:1 ratio because a
heterozygous animal does not give the dominant trait, as would happen in simple dominantrecessive cases
...


In the early 1900s, Thomas Hunt Morgan tried to replicate Mendel’s work using the fruit fly
Drosophila melanogaster
...

Mendel crossed a white-eyed male with normal, pure-breeding red-eyed female and all the
offspring had red eyes
...

When he crossed two of the red-eyed offspring, the next generation was red: white in the ratio
3:1 (as Mendel would have predicted), but all the white-eyed offspring were male
...

Morgan hypothesised that the eye colour gene is carried on the X-chromosome
...

Morgan was awarded a Nobel Prize in 1933
...
If it was homozygous recessive, then the phenotype would be that of
between
the recessive allele
...

heterozygous
– HOWEVER, if it was a case of codominance, heterozygous organisms would have both
genotypes and
phenotypes expressed at the same time, as no allele is totally dominant over the other
...

phenotypes in
examples of codominance
...


–
–
–
–

–

Genes are not the only factor that influence phenotype
GENES + ENVIRONMENT = PHENOTYPE
The environment can control to what extent a genotype is expressed – A lack of sufficient
resources can stunt the growth of a person
Examples:
 Phenylketonuria (PKU): Babies born with PKU cannot make the important enzyme phehydroxylase, and as a result, cannot metabolise the amino acid phenylalanine (phe) into
tyrosine
...
If they eat excessive amounts of phe, the babies will
become severely mentally retarded
...

 Hydrangeas: This flower’s colour is controlled by pigments known as anthocyanins
...
If the hydrangeas grow in acidic environments, the flowers will be bright
blue
...

Factors include:
 Nutrition – identical twins may have different birth weights due to different positions in the
uterus and therefore a difference in nutrition
 Temperature – Himalayan rabbits are black when raised at 5°C, white with black extremities
when raised at 25°C and completely white when raised at 35°C
 pH – hydrangeas have pink flowers in alkaline soils and blue flowers in acidic soils (pH<6)
 Oxygen availability – humans at high altitudes have higher red blood cell counts
 Light – Arctic foxes have dark coats in summer and light coats in winter

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Sandra Sou HSC notes 2017/2018
Students: Notes


Process
information
from
secondary
sources to
construct a
model that
demonstrates
meiosis and
the processes
of crossing
over,
segregation
of
chromosomes
and the
production of
haploid
gametes
...

Identify data
sources and
perform a
first-hand
investigation
to
demonstrate



Aim: To investigate the effect of environment on phenotype
Hypothesis: The plant which receives no water will look different to that which receives less
water
Equipment: Geraniums, soil, water, scissors, tissue
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Sandra Sou HSC notes 2017/2018
the effect of
Safety:
environment
 Soil contains bacteria so hands should be washed after handling soil
on
 Must be careful to keep hands away from the sharp blades of the scissor
phenotype
...
In a small pot, fill soil up to the first ridge, repeat with other plant
2
...
Place into the pot making sure it is the correct orientation
4
...
Water one plant with 50ml of water and don’t water the other
6
...
Record any observations
Results:
Day
Day 1

Observations

Day 2

Day 3

Day 4

Conclusion:

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Sandra Sou HSC notes 2017/2018

4
...

Students Learn to: Notes
–

Describe the
process of DNA
replication and
explain its
significance
...
This term captures the idea that each round of
DNA replication produces hybrid molecules each of which contains one old strand and one
newly synthesized strand
...

The evidence for semiconservative replication was provided several years later by a 1958
paper by Matthew Meselson and Franklin W
...

Conservative: A hypothetic form of replication in which a double-stranded DNA (dsDNA)
produces two daughter dsDNAs, one of which consists of the two original strands whereas
the other daughter DNA consists of two newly synthesized chains
...
A postulated mode of DNA replication
combining aspects of conservative and semiconservative replication; known to be
incorrect
...
The DNA double helix unwinds – Each DNA molecule is a double stranded helix
...

 DNA helicase is the enzyme that unwinds the DNA double helix by breaking
the hydrogen bonds down the centre of the strand
...

2
...
The weak hydrogen bonds break
between the complementary bases of the nucleotides on opposite strands and the
two DNA strands separate, exposing the nucleotide bases
...

3
...
Primer is made up of RNA and tells DNA
polymerase where to go
...
Nucleotides (units made of
sugars – phosphate – base) are picked up by the enzyme DNA polymerase and slotted
in opposite their complementary base partner on each of the existing strands
...
Incorrect base pairing
will result in a change in the DNA base sequence, known as a mutation
...
There are two strands: Leading strand and lagging strand
...
One
of these is called the leading strand, and it is replicated continuously in
the 5’ to 3' direction
...
These short sections are called Okazaki Fragments
...

5
...
The replicated DNA molecules
rewind into the double helix conformation, like the original molecule
...

simple model,
the process by
which DNA
controls the
production of
polypeptides
...
DNA
directs the production of these proteins
...
g
...
e
...
g
...
g
...

Proteins are synthesised in two steps: transcription and translation
...
It involves copying a gene's DNA
sequence to make an RNA molecule
...

o Transcription has three stages: initiation, elongation, and termination
...

o Transcription is controlled separately for each gene in your genome
...

 RNA polymerase is an enzyme that catalyses transcription
...

 mRNA moves out into the cytoplasm
...

 Stage Two: translation – transfer-RNA (tRNA) molecules bring in corresponding amino
acids and attach to the mRNA according to their complementary bases
...

Explain how
mutations in
DNA may lead
to the
generation of
new alleles
...


A mutation is a change in the DNA information on a chromosome
Gene mutation produces NEW ALLELES of genes in species and so creates new genetic
variation
...
It is a
neutral mutation
 VERY RARELY, a mutation will give an organism a phenotypic advantage
...
This mutation cannot be passed on
to offspring
...

Chromosome Mutations:
- Five types exist:
 Deletion
o Due to breakage
o A piece of chromosome is lost

 Inversion
o Chromosome segment breaks off
o Segment flips around backwards

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Sandra Sou HSC notes 2017/2018
 Translocation
o Involves two chromosomes that are not homologous
o Part of one chromosome is transferred to another chromosome

 Nondisjunction
o Failure of chromosomes to separate during meiosis
o Causes gamete to have too many or too few chromosomes
 Duplication
o Occurs when a gene sequence is repeated
Types of Gene Mutations:
 Point mutations
o Change of a single nucleotide
o Includes the deletion, insertion, or substitution of one nucleotide in a gene
o Sickle Cell disease is the result of one nucleotide substitution
o Occurs in the haemoglobin gene
 Substitution
o Mutation that exchanges one base for another
o Can:
 Change a codon to one that encodes a different
amino acid and cause a small change in the
protein produced
...

 Change a codon to one that encodes the same amino acid and causes no
change in the protein produced
...

 Change an amino-acid-coding codon to a single "stop" codon and cause an
incomplete protein
...

 Insertions
o Mutations in which extra base pairs are inserted into a new place in the DNA
...


 Frameshifts
o Inserting or deleting one or more nucleotides
o Changes the reading frame like changing a sentence
o Proteins built incorrectly

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Sandra Sou HSC notes 2017/2018
– Types of Mutations:
 A Change in Chromosome Number:
 ANEUPLOIDY: Is the case of an abnormal number of chromosomes
...
On
fertilisation, there will be an abnormal chromosome number; either too little or
too much
...
g
...

 POLYPLOIDY: This is the case where a cell, or organism, has one or more extra,
complete, sets of chromosomes
...
If it is in a body cell, then it will not spread much
...
Polyploidy is
encouraged in horticulture, as plants with this feature grow larger and stronger
than normal
...





–

As changes in the DNA or chromosomes creates new proteins, this can in turn create new
alleles of genes
This increases variation
...
They may be carcinogens (causing cancer) or teratogens
(causing birth defects)
...

 The ozone ‘hole’ over Antarctica, caused by CFCs, CO, SO2 and oxides of nitrogen,
has led to more intense doses of UV radiation than before
...

 In the 1950s and 1960s, people had their feet X-rayed when buying shoes
...

 Hans Muller received the Nobel Prize in 1927 for showing that genes could
mutate when exposed to X-rays
...

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Sandra Sou HSC notes 2017/2018
 Many scientists who worked with radiation died of cancer, including Marie Curie and
her daughter, who both died of leukaemia
...

 Both survivors and their descendants show immediate damage of the DNA of their
cells (mutations in the sex cells)
...

 Chernobyl also involved a great environmental catastrophe as the radiation with a
long half-life spread into food, soil, land and waterways
...

 As of 2004, it was estimated that half a million people would die prematurely from
radiation-induced cancers
...

Describe the
concept of
punctuated
equilibrium in
evolution and
how it differs
from the
gradual process
proposed by
Darwin
...

 Punctuated equilibrium proposes that, instead of gradual change, there have been
periods of rapid evolution followed by long periods of stability, or equilibrium

Students: Notes

– Analyse

information
from
secondary
sources to
outline the





George Beadle and Edward Tatum hypothesised that one gene controls the production of one
enzyme
...

Because Neurospora is haploid for much of its lifecycle any mutations show up immediately
(even if recessive)
Using X-rays, they produced a mould that was unable to produce a specific amino acid, because
it lacked a necessary enzyme
...

this was
 It was found that if the mould was supplemented with other amino acids, it could grow healthily
...

polypeptide’
 An analysis of each mutant strain showed a difference in one gene which caused a block at one
hypothesis
...

 Beadle and Tatum hypothesised that this mutant mould had lost the ability to make the enzyme
to create this amino acid, because the X-rays had mutated the gene
...
This later became the one protein-one
polypeptide hypothesis because not all proteins are made up of one polypeptide
...


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Sandra Sou HSC notes 2017/2018


Summary:
Changed gene  no enzyme  no reaction  no vitamin
Beadle and Tatum concluded that different genes are involved in making different enzymes
that catalyse different reactions in a cell
...

Process and
analyse
information
from
secondary
sources to
explain a
modern

Golden Staph:
 The use of antibiotics is a selective pressure
...

 For example, Staphylococcus aureus (golden staph) have developed to be resistant to most
modern antibiotics, due to overuse of antibiotics
...

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Sandra Sou HSC notes 2017/2018
example of
 Over many generations (for bacteria this is very quick), the favourable characteristic of
‘natural’
resistance will be more common and the population will be changed by natural selection
...

– Process
Scientist
Work and contribution
Collaboration and
information
Communication
from
James Watson
In 1953, cracked the DNA code with Crick
Worked closely with Francis
secondary
Awarded Nobel Prize in 1962
Crick
sources to
Later he increased understanding of the
Bounced ideas off everywhere,
describe and
genetic code and how DNA triplet code
including Wilkins who showed
analyse the
identifies amino acids and thus controls
them the photograph taken by
relative
protein synthesis
Franklin
importance of
Francis Crick
In 1953, cracked the DNA code with Watson Worked closely with James
the work of:
Awarded Nobel Prize in 1962
Watson
– James Watson
...

genetic information was coded
including Wilkins who showed
– Rosalind
them the photograph taken by
Franklin
...

gel of DNA in early 1950s
Crick
In determining
Showed them the X-ray
Franklin photographed them and Wilkins
the structure of
crystallography photograph
DNA and the
showed the photo to Watson and Crick
without Franklin’s knowledge
impact of the
Awarded Nobel Prize in 1962
or permission
quality of
Rosalind Franklin Used X-ray crystallography to map the
collaboration
Her work was shown to
and
locations of atoms in the DNA molecule
Watson and Crick
communication
First to state that the phosphates lie on the
on their
outside
scientific
Described basic double helical structure
research
...
Current reproductive technologies and genetic engineering have the potential to alter the path
of evolution
...

Artificial pollination
Cloning
...

Selective breeding is the deliberate crossing or mating of individuals of the same
species with the characteristics wanted; over time, these characteristics become
dominant
...

Transport of semen is much easier than transporting a whole animal
...

 DISADVANTAGES: Reduced the genetic variations found in populations, making
them susceptible to changes in the environment (e
...
new disease)

–

Artificial Pollination:
 Plant breeders carry out artificial pollination to breed plants with specific
characteristics (like Mendel did)
...
It is then dusted onto the female
stigma of another plant
...
No expensive equipment required
 DISADVANTAGES: Genetic variation reduced

–

Cloning:
 Cloning is a method of producing genetically identical organisms
 A clone is a collection of genetically identical copies
 PLANT CLONING:
 The most commonly used method, and the oldest, is cutting and grafting
...
The plant that grows is a clone of the
original plant
 Tissue culture technology has allowed mass cloning of plants
...
The cells are grown on a nutrient medium, and
incubated under controlled conditions
...

 ANIMAL CLONING:
 Much more difficult than plant cloning
 First animal to be cloned was Dolly
 Technique used is called “nuclear transfer technology”:
1
...
Nucleus removed from one of these cells and placed in an
enucleated egg cell (egg cell with genetic info removed)
Page | 34

Sandra Sou HSC notes 2017/2018

Gentle electric pulse causes nucleus to fuse with egg cell
A second electric pulse starts cell division and embryo formation
This new cell is implanted into a female sheep where it grows into a
new organism
 ADVANTAGES: In agriculture, cloned plants have identical requirements and
grow in similar ways to produce similar yields at the same time
...

Cloning is expensive with limited advantages over reproductive techniques
...
The health/life expectancy of cloned animals is questionable, with
the death of Dolly the sheep being earlier than expected
...

4
...


– Outline the processes

used to produce
transgenic species
and include examples
of this process and
reasons for its use
...
A useful gene, and the chromosome it is on, is identified
2
...
Separate DNA sequences for regulation may have to be added to ensure
the gene will work
4
...
Sometimes a vector
is used to do this
...
Special enzymes, called restriction enzymes
are used
...
They cut DNA by breaking the
hydrogen bonds in a triplet – the ends are called “sticky ends”
 Making Recombinant DNA: The DNA strands from 2 organisms are cut using the
same enzyme, the sticky ends will match
...
This is called ANNEALING
...

 Making Trangenes: An isolated gene cannot function if it is transferred alone
...
The chemicals are specific to many pests and do not kill other insects
...
They produce their own BT chemicals, and no longer need to be sprayed
 COLD STRAWBERRIES: A gene from a type of salmon that allows it to survive
cold temperatures has been isolated, and inserted into a strain of strawberry
...

 BACTERIAL INSULIN: Diabetics previously obtained their insulin from animals,
esp
...
The gene for insulin production, taken from the human pancreas, was
placed in to the DNA of a bacterium
...


–

Ethical Issues of Transgenesis:
 These technologies help treat diseases and increase food production
 Should we be tampering with nature in this way?
 Is it right to change living organisms for commercial gain?
 Transgenesis disrupts evolutionary relationships between organisms
 If a transgenic species was released into the natural environment, it could
outcompete the natural organisms
 Health-risks and side effects with eating GM foods
...
g
...
The main crop being grown all over the world is BT cotton
...
If all cotton grown all over
plant and animal
the world is BT, and a disease appears, that kills specifically BT cotton, than
example that have
there is a risk of cotton becoming an extinct organism
been genetically
– In another case, a population of cattle that have all been fathered by the same bull,
altered
...

Students: Notes
–

–

Process information
from secondary
sources to describe a
methodology used in
cloning
...


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