1. Inheritance of Traits
DSRU EP M3

2. Boy or Girl? X X Y
“Allele” XX XY
Girl
Boy

3. Mother
Boy or Girl?
Son
Daughter
Father

4. Key words Gamete Zygote Allele Dominant Recessive Homozygous
Heterozygous
This allele determines the development of a characteristic
This is formed when an egg is fertilised by a sperm
This allele will determine a characteristic only if there are no dominant ones
This word refers to a pair of chromosomes being made of two different alleles of a gene
An egg or a sperm are called this
This word refers to a pair of chromosomes being made of two of the same alleles of a gene
An alternative form of a gene

5. Genes, Chromosomes and DNA

6. How genes work Some facts: - Made up of paired bases
- Contain instructions on what a cell does, how the organism should work etc
- The instructions are in the form of a code
- The code is made up from the four bases that hold the strands together
- The bases represent the order in which amino acids are assembled to make proteins
- Each group of 3 bases represents one amino acid
- There are only about 20 amino acids

7. The structure of DNA
DNA contains information that determines inherited characteristics. DNA is made of very long strands which have four different compounds called bases. A sequence of three of these bases is the code for making a an amino acid. The order of bases on a DNA molecule controls the order in which amino acids are assembled to produce a particular protein

8. Mutations
Mutations are changes in the structure of the DNA molecule. They can be passed on to daughter cells through cell division. They will result in the wrong proteins being produced.
Mutations can be caused by:
- Ionising radiation (UV, X-rays etc)
- Radioactive substances
- Certain chemicals
Effects:
- Mostly harmful
- Causes death or abnormality in reproductive cells
- Causes cancer in body cells
- Some CAN be neutral or even beneficial (e.g. the peppered moth)

9. What would the offspring have?
Eye colour
In eye colour the brown eye allele is dominant, so we call it B, and the blue eye is recessive, so we call it b: BB Bb bb
Homozygous brown-eyed parent
Heterozygous brown-eyed parent
Blue-eyed parent
What would the offspring have?

10. X X Eye colour BB bb Bb Bb (FOIL)
Example 1: A homozygous brown-eyed parent and a blue-eyed parent:
Example 2: 2 heterozygous brown-eyed parents BB bb Bb Bb X X
Parents: B b B b B b
Gametes:
(FOIL) Bb Bb Bb Bb BB Bb bB bb
Offspring:
All offspring have brown eyes
25% chance of blue eyes

11. Eye colour
Example 3: A heterozygous brown-eyed father and a blue-eyed mother: Bb bb
Equal (50%) chance of being either brown eyed or blue eyed. B b b Bb Bb bb bb

12. B b B b Bb bb Another method
Example 3: A heterozygous brown-eyed father and a blue-eyed mother: B b B b Bb bb
Father
Mother

13. Example questions
1) In mice, white fur is dominant. What type of offspring would you expect from a cross between a heterozygous individual and one with grey fur? Explain your answer with a genetic diagram.
2) A homozygous long-tailed cat is crossed with a homozygous short-tailed cat and produces a litter of 9 long-tailed kittens. Show the probable offspring which would be produced if two of these kittens were mated and describe the characteristics of the offspring (hint: work out the kitten’s genotype first).

14. X X X Inherited diseases Ff Cc cc Ss
1) Cystic fibrosis – a disease that causes thick and sticky mucus to coat the lungs, gut and pancreas. It’s caused by recessive alleles: Ff X
2) Huntingdon's disease – a disease of the nervous system that causes shaking and eventually dementia. It’s caused by a dominant allele: Cc cc X
3) Sickle cell anaemia – a disease that alters the shape of red blood cells, thereby reducing their oxygen capacity, causing weakness and anaemia. It’s caused by recessive alleles: Ss X

15. X Modern Genetics Mendel’s experiment:
My name is Gregor Mendel. I am the father of modern genetics because of the work I did on pea plants in 1865…
Mendel’s experiment: X
Take two plants; one which is pure-bred for tallness and one pure-bred for shortness, and cross them:

16. Now cross two of these plants…
Modern Genetics
All the plants produced were tall.
Now cross two of these plants…
3 out of every 4 plants were tall, leading Mendel to hypothesise that “for every characteristic there must be two determiners”

17. Words – clones, damp, independent, roots, identical
Plants can reproduce ASEXUALLY. The offspring are genetically ________ to the parent plant and are called _________. Two examples:
1) This spider plant has grown a rooting side branch (“stolon”) which will eventually become __________.
2) A gardener has taken cuttings of this plant (which probably has good characteristics) and is growing them in a ____ atmosphere until the ____ develop.
Words – clones, damp, independent, roots, identical

18. Cloning
1) Cloning plants:
2) Cloning sheep:

19. Selective breeding Friesian Jersey Hereford
I raise cows. Each type of cow is good at a certain job. The Friesian cow produces large quantities of milk, the Jersey cow produces very nice milk and the Hereford cow produces lot of beef.
Friesian
Jersey
If, for example, I want lots of milk I would only breed Friesian cows with each other – this is SELECTIVE BREEDING.
Hereford

20. Selective breeding vs. Cloning
Advantages
Disadvantages
Cloning
Selective breeding

21. Selective breeding vs. Cloning
Advantages
Disadvantages
Cloning
Allows large numbers of organisms with good characteristics to be produced
Very efficient
Causes reduced numbers of alleles
Loss of variation could harm survival chances if the environment changes
Selective breeding
Produced organisms with favoured characteristics
Very efficient and economically viable

22. Genetic Modification
Possible uses of genetic modification of organisms:
Improving crop yield
Improving resistance to pesticides
Extend shelf-life
Manufacture a certain chemical (e.g. insulin)
Convenience

23. Genetic engineering
Insulin is a hormone produced by the pancreas to help control blood sugar levels. Diabetics can’t produce enough insulin and often need to inject it.
Insulin can be made by genetic engineering:

24. Genetic engineering - Insulin
Step 1: Using RESTRICTION ENZYMES “cut out” the part of the human chromosome that is responsible for producing insulin.
Step 2: Using another restriction enzyme cut open a ring of bacterial DNA (a “plasmid”). Other enzymes are then used to insert the piece of human DNA into the plasmid.
Step 3: Place the plasmid into a bacterium which will start to divide rapidly. As it divides it will replicate the plasmid and make millions of them, each with the instruction to produce insulin. Commercial quantities of insulin can then be produced.

25. Evolution
Charles Darwin ( )

26. Evolution
Evolution is the slow, continual change of organisms over a very long time. All living things on the Earth have developed from the first simple life forms that arrived 3,000,000,000 years ago.
One of the effects of evolution is that species will become better adapted to their environment. If these species don’t adapt they may become extinct due to being unable to deal with any of these factors…
Increased competition
Changes in the environment
New diseases
New predators

27. Evolution My key observations:
All living things produce more offspring than survive to adulthood
In spite of this, population sizes remain roughly constant
Variation exists among species
Characteristics can be passed on from one generation to the next.
These observations led me to the conclusion that species evolve over a along period of time by a mechanism called “Natural Selection”. The main evidence for this is from fossil records.

28. Natural Selection 1) Each species shows variation:
There is competition within each species for food, living space, water, mates etc
Get off my land
The “better adapted” members of these species are more likely to survive – “Survival of the Fittest”
Gutted!
Yum
These survivors will pass on their better genes to their offspring who will also show this beneficial variation.

29. A smaller example…
Consider the four steps of natural selection in the example of some bacteria that has become resistant to penicillin:
Variation – some strains of bacteria are resistant and some aren’t.
Competition – The non-resistant bacteria are killed by the penicillin.
Survival of the fittest – the resistant bacteria survive.
Passing on of genes – the resistant bacteria reproduce and pass on their adaptations to their offspring.
Bacteria
Penicillin