162022 Inheritance and Survival Yum Variation 162022 Variation

1/6/2022 Inheritance and Survival Yum!

Variation 1/6/2022 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

Environmental differences 1/6/2022 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

Where is this information stored? 1/6/2022 Section of a chromosome: Genes for blood group: Genes for eye colour Genes for hair colour Different species have different numbers of chromosomes. Humans have 46 (23 pairs) in every cell.

Sexual Reproduction 1/6/2022

Sexual Reproduction 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”). 1/6/2022

Sexual vs. Asexual reproduction 1/6/2022 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”)

Mitosis Each daughter cell has the same number of chromosomes and genetic information as the parent. 1/6/2022

Meiosis Each daughter cell has half the number of chromosomes of the parent. 1/6/2022

Mitosis vs. Meiosis Mitosis: Meiosis: 1. Used for growth and repair of cells 2. Used in asexual reproduction 3. Cells with identical number of chromosomes and genetic information are produced 1/6/2022 Used to produce gametes for sexual reproduction 2. Each daughter cell has half the number of chromosomes of the parent

Boy or Girl? X Y 1/6/2022 X “Allele” Girl XX XY Boy

Mother Boy or Girl? 1/6/2022 Son Father Daughter

Growing up 1/6/2022 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

The Menstrual Cycle: 1/6/2022 Empty follicle – gradually disappears

The Menstrual Cycle: Hormone concentration Oestrogen – produced in the _______ and causes the lining of the uterus to ______ 1/6/2022 Progesterone – produced by the empty ____ and maintains the ______. If egg is _______ progesterone continues to be produced Words – follicle, lining, ovaries, thicken, fertilised

Fertility 1/6/2022 The events that happen in a female body during the menstrual cycle are triggered by hormones (chemical messengers). Artificial hormones can be used to: 1) Stimulate the release of eggs (fertility treatment) 2) 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.

Fertility 1/6/2022 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 2: The rising levels of oestrogen cause the pituitary gland to stop producing FSH and produce LH instead Step 3: LH stimulates the release of the mature egg in the middle of the menstrual cycle Artificial fertility: 1) To INCREASE fertility FSH is given to stimulate maturation of eggs. 2) To DECREASE fertility oestrogen is given (“The Pill”) to inhibit FSH production stopping eggs from maturing.

Genes, Chromosomes and DNA 1/6/2022

How genes work 1/6/2022 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

Mutations 1/6/2022 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)

Phenotype Zygote Key words 1/6/2022 • This allele determines the development of a characteristic • This is formed when an egg is fertilised by a sperm Haploid no. • This allele will determine a characteristic only if there are no dominant ones Dominant • This word refers to a pair of chromosomes being made of two different alleles of a gene Recessive • The characteristics a genotype (e. g. Bb) produce Homozygous • 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 Heterozygous

Eye colour 1/6/2022 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

Eye colour Example 1: A homozygous brown-eyed parent and a blue -eyed parent: X BB Parents: Gametes: 1/6/2022 Example 2: 2 heterozygous brown-eyed parents bb Bb X Bb B B b b B b Bb Bb BB Bb b. B bb (FOIL) Offspring: All offspring have brown eyes 25% chance of blue eyes

Eye colour 1/6/2022 Example 3: A heterozygous brown-eyed father and a blue-eyed mother: Bb bb B b b b Bb Bb bb bb Equal (50%) chance of being either brown eyed or blue eyed.

Another method Example 3: A heterozygous brown-eyed father and a blue-eyed mother: Father B b b Bb bb Mother 1/6/2022

Example questions 1/6/2022 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).

Inherited diseases 1/6/2022 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 Ff 2) Huntingdon's disease – a disease of the nervous system that causes shaking and eventually dementia. It’s caused by a dominant allele: Cc X cc 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 Ss

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 1/6/2022

Genetic engineering 1/6/2022 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:

Genetic engineering - Insulin 1/6/2022 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.

Evolution Charles Darwin (1809 -1882) 1/6/2022

Evolution 1/6/2022 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 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… 1) Increased competition 2) Changes in the environment 3) New diseases 4) New predators

Evolution 1/6/2022 My key observations: 1) All living things produce more offspring than survive to adulthood 2) In spite of this, population sizes remain roughly constant 3) Variation exists among species 4) 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.

Natural Selection 1/6/2022 1) Each species shows variation: Get off my land 2) There is competition within each species for food, living space, water, mates etc 3) The “better adapted” members of these species are more likely to survive – “Survival of the Fittest” Gutted! Yum 4) These survivors will pass on their better genes to their offspring who will also show this beneficial variation.

A smaller example… 1/6/2022 Consider the four steps of natural selection in the example of some bacteria that has become resistant to penicillin: Bacteria 1) Variation – some strains of bacteria are resistant and some aren’t. 2) Competition – The non-resistant bacteria are killed by the penicillin. 3) Survival of the fittest – the resistant bacteria survive. Penicillin 4) Passing on of genes – the resistant bacteria reproduce and pass on their adaptations to their offspring.

Selective breeding 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. 1/6/2022 Friesian Jersey If, for example, I want lots of milk I would only breed Friesian cows with each other – this is SELECTIVE BREEDING. Hereford

Selective breeding vs. Cloning 1/6/2022 Advantages Cloning Selective breeding Disadvantages

Selective breeding vs. Cloning 1/6/2022 Advantages Cloning Selective breeding Disadvantages 1) Allows large numbers 1) Causes reduced of organisms with numbers of alleles good characteristics 2) Loss of variation to be produced could harm survival 2) Very efficient chances if the environment changes 1) Produced organisms with favoured characteristics 2) Very efficient and economically viable 1) Causes reduced numbers of alleles 2) Loss of variation could harm survival chances if the environment changes