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GeneticsSarah Jones

• 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 inheritance.

• 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 molecules.

• 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 a rung.

• Remember – At The Gold Coast

• Nucleotide – consists of a sugar, phosphate and base.

• Gene – a segment of DNA that codes for a protein, which in turn codes for a trait.– Skin tone, eye colour etc.

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• 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.

blueprintsforliving.com

• 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.

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• Organism• Cell • Nucleus• Chromosome• DNA • Gene

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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 University, England.

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 science.

Franklin

Wilkins

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.

Watson

Crick

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.

learn.crystallography.org.uk

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.

www.lifesciencesfoundation.org

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.

Chromosomes• 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, haemophilia.

en.wikipedia.org

Chromosomes• Humans contain 23 pairs• Chromosomes determine if you are male or

female.

Humans have 46 chromosomes – 23 from each parent.

• 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 same.

• Fraternal twins occur when two eggs are fertilised – the twins are not genetically the same.

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Meiosis• 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 humans (2n).

• Gametes, sex cells, only have one set of chromosomes (23).

• This is referred to as the haploid number for humans (n).

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.

Pea Plants• One of the main variations Mendel noted was

that some peas were smooth and some wrinkled.

• When he cross bred these peas – using the pollen from the flowers, he noted that all of the offspring were smooth.

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He then took smooth peas and cross pollinated these plants – he noted that ¾ of the peas were smooth and ¼ wrinkled.

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• 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 recessive.

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Punnett Square

w w

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.

Second Generation

S w

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 or wrinkled.

• Homozygous – contains only one type of gene e.g. SS or ww

• Heterozygous – two types of genes e.g. Sw

Guinea Pigs• Short fur is dominant (F) and long fur

recessive (f).• If a heterozygous guinea pig mated with a

homozygous long hair guinea pig we would get the following results.

F ff Ff fff Ff ff

50 % Short fur and 50% Long fur

• Brunette hair is dominant and blonde recessive.

• Therefore, if the parents genes are homozygous brunette and blonde all offspring will be brunette.

B Bb Bb Bbb Bb Bb

Incomplete Dominance• 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.

animal-world.com

Genetic Pedigrees

Huntington’s Disease• 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 function.

• There is no cure.

macintosh-genetic-disorders.wikispaces.com

• H is the gene for Huntington's which is dominant.

Cystic Fibrosis• A hereditary disease which affects the entire

body, causing progressive disability and often early death.

• a is the affected allele and A not affected

Haemophilia• 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 the disorder.

• 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 to it.

• Females must have the gene on both X chromosomes to have haemophilia.

Queen Victoria was a carrier of the haemophiliac gene.

Genetic Mutations

• Colour Blindness• Down Syndrome• Albinism• Cystic fibrosis• Haemophilia• Tay-Sachs Disease• Turner Syndrome

Genetic Modifications• 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 nutrient value.

Canola Modification• 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.

www.abc.net.au

Rice Modifications• 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.

www.21stcentech.com