1. Inheritance and Survival
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Inheritance and Survival
Yum!

2. Variation
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Variation means “differences within a species. For example, consider some of the people in your class:
Ways in which they are the same
Ways in which they are different

3. Environmental differences
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Some of this variation is due to our parents, but some of it is due to our upbringing and the environment in which we live – this is called “Environmental variation”.
Variation due to inheritance only
Variation due to environment only
Variation due to a bit of both

4. Where is this information stored?
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Section of a chromosome:
Genes for eye colour
Genes for blood group:
Genes for hair colour
Different species have different numbers of chromosomes. Humans have 46 (23 pairs) in every cell.

5. 19/11/2018
Sexual Reproduction

6. Sexual Reproduction
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The human egg and sperm cell contain 23 chromosomes each (the “haploid number).
When fertilisation happens the gametes fuse together to make a single cell called a ZYGOTE. The zygote has 46 chromosomes (23 pairs – the “diploid number”).

7. Sexual vs. Asexual reproduction
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Sexual reproduction:
2 parents are needed
Offspring will have “pairs” of chromosomes
This will cause genetic variation
Asexual reproduction:
Only 1 parent needed
Offspring are genetically identical to parent (“clones”)

8. Mitosis
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Each daughter cell has the same number of chromosomes and genetic information as the parent.

9. Each daughter cell has half the number of chromosomes of the parent.
Meiosis
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Each daughter cell has half the number of chromosomes of the parent.

10. Mitosis vs. Meiosis Mitosis: Meiosis:
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Mitosis:
Used for growth and repair of cells
Used in asexual reproduction
Cells with identical number of chromosomes and genetic information are produced
Meiosis:
Used to produce gametes for sexual reproduction
Each daughter cell has half the number of chromosomes of the parent

11. Boy or Girl?
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“Allele” XX XY
Girl
Boy

12. Boy or Girl?
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Mother
Son
Daughter
Father

13. Growing up
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A number of changes happen when children grow up and go through puberty. These are called “secondary sexual characteristics” and are triggered by rising levels of oestrogen in girls (made in the ovaries) and testosterone in boys (made in the testes):
Girls
Boys

14. Empty follicle – gradually disappears
The Menstrual Cycle:
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Empty follicle – gradually disappears

15. Words – follicle, lining, ovaries, thicken, fertilised
The Menstrual Cycle:
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Hormone concentration
Oestrogen – produced in the _______ and causes the lining of the uterus to ______
Progesterone – produced by the empty ________ and maintains the ______. If egg is _______ progesterone continues to be produced
Words – follicle, lining, ovaries, thicken, fertilised

16. Fertility
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The events that happen in a female body during the menstrual cycle are triggered by hormones (chemical messengers). Artificial hormones can be used to:
Stimulate the release of eggs (fertility treatment)
Inhibit the release of eggs (contraceptive pills)
In normal circumstances natural hormones are responsible for releasing the egg and for thickening the lining of the womb. These hormones are produced by the pituitary gland in the brain and in the ovaries.

17. Fertility
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3 hormones are involved in the menstrual cycle: oestrogen, LH and FSH. Here’s how:
Step 1: FSH produced by the pituitary gland causes both an egg to mature and the ovaries to start producing oestrogen
Step 3: LH stimulates the release of the mature egg in the middle of the menstrual cycle
Step 2: The rising levels of oestrogen cause the pituitary gland to stop producing FSH and produce LH instead
Artificial fertility:
To INCREASE fertility FSH is given to stimulate maturation of eggs.
To DECREASE fertility oestrogen is given (“The Pill”) to inhibit FSH production stopping eggs from maturing.

18. Genes, Chromosomes and DNA
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19. How genes work Some facts: - Made up of paired bases
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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

20. Mutations
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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)

21. Key words Phenotype Zygote Haploid no. Dominant Recessive Homozygous
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Phenotype
Zygote
Haploid no.
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
The characteristics a genotype (e.g. Bb) produce
This word refers to a pair of chromosomes being made of two of the same alleles of a gene
The number of chromosomes from a parent

22. Eye colour
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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? – This is an example of monohybrid inheritance

23. X X Eye colour BB bb Bb Bb (FOIL)
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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

24. Eye colour
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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

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

26. Example questions
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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).

27. X X X Inherited diseases Ff Cc cc Ss
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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

28. Genetic Modification
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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

29. Genetic engineering
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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:

30. Genetic engineering - Insulin
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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.

31. Evolution
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Charles Darwin ( )

32. Evolution
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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

33. Evolution My key observations:
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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.

34. Natural Selection 1) Each species shows variation:
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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.

35. A smaller example…
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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

36. Selective breeding Friesian Jersey Hereford
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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

37. Selective breeding vs. Cloning
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Advantages
Disadvantages
Cloning
Selective breeding

38. Selective breeding vs. Cloning
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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