• Deoxyribonucleic acid (DNA) is a molecule
that contains all of the information that
determines who you are and what you look
like. The “Blueprint of Life”.
• In 1869 Friedrich Miescher isolated chemicals
that were later called nucleic acids. This lead
to the identifications of DNA as the carrier of
• In 1953 James Watson and Francis Crick
established the ‘double helix’ shape of DNA.
• The sides of the ladder like structure are a
chain of alternating sugar and phosphate
• The rungs of the ladder are bases that are
attached to the sugar molecules.
• Each rung is made up of two
chemicals called bases.
– Adenine (A)
– Thymine (T)
– Guanine (G)
– Cytosine (C)
• Base Pairs: A-T and G-C linked form
• Remember – At The Gold Coast
• Nucleotide – consists of a sugar, phosphate
• Gene – a segment of DNA that codes for a
protein, which in turn codes for a trait.
– Skin tone, eye colour etc.
• DNA contains the coding that makes up the
building blocks of you body – amino acids.
• Amino acids join together to make proteins
and proteins are used to make new cells.
• There are 20 amino acids.
• Amino acids are coded by combinations of
three bases – AAA and AAG both make the
amino acid phenylalanine.
• Triplet codes GGA, GGG, GGT and GGC make
the amino acid proline.
Rosalind Franklin, Maurice Wilkins,
James Watson and Francis Crick
The main people responsible for the
discovery of DNA are Rosalind Franklin and
Maurice Wilkins from a research unit at
King's College, London, and James Watson
and Francis Crick from Cambridge
The story of Rosalind Franklin would have
been quite different if she were born male.
During the middle of the twentieth century,
women were not encouraged to study
Franklin researched X-ray
crystallography, a method of
determining the structure of crystals
based on the use of X-rays.
Rosalind contributed to the
development of this technology by
pioneering its use in analysing a variety
of substances, including DNA.
The Cambridge team of Watson and
Crick made a failed model of DNA and
were told to stop their research.
Franklin mostly worked alone because
she and Wilkins could not get along.
He assumed she was to assist his work
while Franklin assumed she would be
the only one working on DNA.
Franklin suspected that all DNA had a
helix structure but did not want to
announce this finding until she had
sufficient evidence. Wilkins was
frustrated and showed Franklin's
results to Watson without her
knowledge or consent.
The information Watson and Crick received from
Wilkins was crucial to the ultimate discovery of
DNA. It was principally these X-ray diffraction
techniques developed by Franklin that allowed
Watson and Crick to suggest the double helix
structure for DNA.
The work of Wilkins and Franklin was
acknowledged in this paper. The structure so
perfectly fit the experimental data that it was
accepted almost immediately.
Rosalind Franklin died of
cancer in 1958 at the age
of 37. In 1962 the Nobel
Prize for physiology and
medicine went to James
Watson, Francis Crick and
Maurice Wilkins for their
role in the discovery of the
structure of DNA.
• The way living things pass on traits – skin
tone, eye colour etc.
• Chromosomes are formed of a single DNA
molecule that contains many genes.
Some of our worst diseases result from
chromosomes that have failed to function
correctly e.g. polycystic kidney disease,
Huntington’s disease, sickle cell anaemia,
• Humans contain 23 pairs
• Chromosomes determine if you are male or
Humans have 46 chromosomes – 23 from each
• Sex cells – ova and sperm only have half of the
number of chromosomes as the rest of the
cells in your body.
• Ova – only X
• Sperm – X or Y therefore, your father
determines your sex.
• Identical twins occur when a fertilised egg
divides in two – the babies are genetically the
• Fraternal twins occur when two eggs are
fertilised – the twins are not genetically the
• Mitosis is cell division where a cell reproduces
by splitting to form two identical offspring.
• Meiosis is cell divisions that only happens in
the reproductive organs – ovaries and testes.
• Meiosis produces cells which have half the
number of chromosomes.
• The nucleus of normal human body cells
consist of 46 chromosomes or 23 pairs of
chromosomes (2 of each chromosome).
• This is referred to as the diploid number for
• Gametes, sex cells, only have one set of
• This is referred to as the haploid number for
Fertillisation is the fusion of haploid male and
female gametes, to form a diploid number of
chromosomes in a zygote.
Gregor Mendel 1822-1884
• An Austrian monk who worked on his garden
at the monastery and noted how the
characteristics of plants were passed on from
one generation to the next.
• The results of Mendel's research became the
foundation of modern genetics.
• One of the main variations Mendel noted was
that some peas were smooth and some
• When he cross bred these peas – using the
pollen from the flowers, he noted that all of
the offspring were smooth.
He then took smooth peas and cross pollinated
these plants – he noted that ¾ of the peas were
smooth and ¼ wrinkled.
• Mendel realised that the peas had two factors
inside of them – one from each parent.
• Smooth peas – SS
• Wrinkled peas – ww
• Mendel deduced that the smooth factor
(gene) is dominant and the wrinkled factor is
S Sw Sw
S Sw Sw
When these two peas SS and ww were crossed all of
the offspring were smooth because S is dominant.
S SS Sw
w Sw ww
¼ of offspring were wrinkled.
• Genotype – the type of genes e.g. SS and ww the
dominant gene is always written as a capital.
• Alleles – the possible genes in the sex cells
e.g. S and w
• Phenotype – how the genotype displays e.g. smooth
• Homozygous – contains only one type of gene e.g. SS
• Heterozygous – two types of genes e.g. Sw
• Short fur is dominant (F) and long fur
• If a heterozygous guinea pig mated with a
homozygous long hair guinea pig we would
get the following results.
f Ff ff
f Ff ff
50 % Short fur and 50% Long fur
• Brunette hair is dominant and blonde
• Therefore, if the parents genes are
homozygous brunette and blonde all offspring
will be brunette.
b Bb Bb
b Bb Bb
• Purebred budgies are yellow and blue birds.
• Green budgies result from one parent with
blue feathers and one with yellow.
• Both parents are homozygous and the two
alleles are not dominant or recessive and
result in a blend of characteristics.
• A neurological condition caused by the
inheritance of a defective gene.
• The death of brain cells leads to the gradual
loss of cognitive, physical and emotional
• There is no cure.
• H is the gene for Huntington's which is dominant.
• A hereditary disease which affects the entire
body, causing progressive disability and often
• a is the affected allele and A not affected
• Passed from one generation to the next
through the X (female) chromosome.
• Disease in which blood does not clot normally.
• Because the blood clots so slowly there is a
constant danger of bleeding to death even
with a minor injury.
• Women transmit the disease, however, only
men exhibit it.
• Women who carry haemophilia have the gene
on one of their X chromosomes.
• Since the gene is recessive, they do not have
• If a male has the bad gene they will be a
haemophiliac because there is no matching
gene on his Y chromosome to be dominant
• Females must have the gene on both X
chromosomes to have haemophilia.
Queen Victoria was a carrier
of the haemophiliac gene.
• In GM organisms the genetic information has
be changed by inserting new genes.
• The new genes are then passed to daughter
cells through mitosis.
• GM is used to create desirable
traits in organisms such as
insect resistance and increased
• Western Australia, Victoria and New South
Wales all have farmers growing GM canola.
• This canola is resistant to herbicides that are
commonly used to control weeds.
• Therefore, the farmers can kill the weeds
using chemicals and not affect their canola.
• White rice is a main food source for half the
worlds population, however, it lacks essential
minerals and vitamins (Vitamin A deficiency can
lead to blindness in children).
• Golden rice-21 is genetically modified using the
genes from corn, daffodils and bacteria. The rice
contains beta-carotene which the body converts
to vitamin A.