Demonstrate understanding of biological ideas relating to genetic variation.

1. Demonstrate understanding of biological ideas relating to genetic variation. Science A.S. 1.9 2014

2. The Structure of DNA DNA (deoxyribonucleic acid) is found in the nucleus of living cells Its structure is described as a double helix

3. Nucleotide Bases • There are four bases • Adenine (A) always bonds with Thymine (T) • Cytosine (C) always bonds with Guanine (G) • The bases determine your genetic code. Animation of DNA in the body

4. Chromosomes • DNA is divided into “chunks” called Chromosomes • In humans most cells contain 46 chromosomes arranged into 23 homologous pairs. • XX pair is a female • XY pair is a male

5. Genes • Each chromosome is divided up into genes. • Genes are specific sequences of bases that code for proteins • When proteins fold correctly they give us our traits, such as fixed or free earlobes • Traits are heritable if the information can be passed on via the gametes • non-heritable traits cannot be passed on • Mutations in somatic cells are non-heritable

6. Alleles -alternative forms of the same gene • Every somatic (body) cell has 23 homologous pairs of chromosomes. • So each cell has a pair of genes, called alleles, coding for every trait. • They may be homozygous (the same) e.g AA • Or heterozygous (different) e.g. Aa • The alleles are created by chance mutationsbut they may benefit the organisms survival.

7. Alleles may be dominant or recessivedepending on whether the trait is seen. A dominant allele is always expressed whether an individual has one or two copies of the allele. Alleles (cont)

8. Phenotype • The characteristics displayed are known as phenotype. • Recessive • blue eyes • Small letter • Dominant • hitchhikers thumb, tongue roll • Capital letter • If the phenotype is advantageous the species is more likely to survive if the environment changes.

9. Genotytpe is the genetic make up of an individual E.g. Tongue roll alleles are represented by T or t What are the 3 possible genotypes? TT, Tt, tt What is the genotype and phenotype of the children ? Genotype Tt, phenotype can roll Genotype

10. Sex Determination • The gonads (testes and ovaries) produce the gametes (sperm and egg) • Gametes are sex cells and only have 23 single chromosomes (haploid). Why? • During fertilisation the egg and sperm fuse to form a zygote with 23 pairs of chromosomes. (diploid)

11. COLOUR BLINDNESS What do you see here? DO NOT CALL OUT!

12. Sex Determination • Sex is determined by the presence of the Y chromosome • XY = male and XX = female • The female donates one of her two X chromosomes • The male either an X or a Y • Each mating is independent of the previous so there is always a 50:50 ratio of males and females • Small population sizes often mask the 50% ratio Sex determination clip

13. Sometimes It goes Wrong! • Xo Turners syndrome • XXY Kleinfelters syndrome • XXX Metafemale • XYY male Achondroplasia

14. DNA Replication • When cells divide each new cell must contain a copy of the DNA. • In order for this to occur DNA replication needs to take place. • Double stranded DNA is unwound by enzymes so 2 single strands are exposed. • Nucleotide bases are matched up to these templates in a process known as complimentary base pairing.

15. DNA Replication (cont) • Each strand of the original acts as a template for building the new molecule. • This process in known as semi conservative replication. • So each new cell has DNA made up of 1 original and 1 new strand. Replication video

16. Cell Division • 2 types Mitosis • Occurs in body cells • Exact copy • Growth/repair of organism Meiosis • Occurs in GONADS • Results in half the chromosomes • Produces variation in the gametes (sex cells)

17. MITOSIS This single cell is copied repeatedly to form an adult with approximately 10,000,000,000,000 cells – all with exactly the same information. How does this copying take place? • Each chromosome copies its information and is now called a chromatid. 2. The chromatids line up in the middle of the cell. 3. Half of each chromatid goes to each end of the cell. 4. Two new identical daughter cells are formed. See an animation of Mitosis

18. MEIOSIS Meiosis is the special type of cell division that creates gametes. Why is it necessary to half the amount of information passed on? Two gametes (one from each parent) fuse to form azygote. A child is born How does meiosis happen? Square dance 1. Chromosomes double, just like in Mitosis. 2. The chromatids pair up and “cross over’ information. Half go one way and half the other. 3. Two new cells are made. 4. The chromatids line up and divide again to form four cells. Each with one set of information. Diploid = 2 sets of chromosomes Mitosis /meiosis test Haploid = 1 set of chromosomes

19. Asexual Reproduction • All offspring are identical (clones) Advantage • Quick population growth • No partner needed • If the environment is “right” then the organism can reproduce immediately and all the offspring will thrive because they are identical to the parent Disadvantage • Kill one, kill all • If the environment is “bad” for the parent it will be bad for all the offspring • Human intervention – cuttings, genetic engineering • Strawberry runners • Aphids

20. Sexual Reproduction • Offspring are different from parents (variation) Advantage • Survival of the fittest (finches) • If environmental change occurs, increased chance of species survival. Disadvantage • Need a partner!? • Energy wastage

21. Survival of the Fittest • Genes code for proteins which give species their characteristics. • When DNA is copied, mutations can randomly occur. • Sometimes the “mistakes” create new traits which make the individual better adapted to survive in their environment.

22. Polar Bear Adaptations Thick white fur - Skin - Big paws - Claws - Ears/Tail - Teeth - Fat layers – Nostrils - • Thick white fur - camouflage in the snow and warmth (it's actually hollow) • Skin - black to absorb heat from the Sun • Big paws - spread body weight, traction, aid swimming • Claws - curved to dig and catch fish • Ears/Tail - short to minimise heat loss • Teeth - jagged to suit a carnivore • Fat layers – insulate against the cold • Nostrils - close underwater

23. Alleles – alternative forms of the same gene created by mutation. • Alleles are assigned letters to distinguish one from another. • E.g. The gene is for fur diameter • but the alleles are thick (T) and thin (t). A polar bear with the thick allele would be better insulated against the Arctic weather. It would be “fitter” than others and more likely to pass on it’s genes to future generations.

24. Test Yourself Discuss how and why the ratio of the alleles for skin colour and fur diameter might change if the planet continues to heat up. (T stands for thick fur, t stands for thin, B stands for black skin, b stands for white)

25. MUTATIONS Mutations are changes in genetic material that can be passed on during cell replication. They are caused by Mutagens. Pathogens (Microbes and viruses) Radiation (Nuclear and Solar) Chemicals (smoking, herbicides, pollutants, diet, etc.) A carcinogen is a cancer causing mutagen. Mutations change the base sequence of DNA in a cell and therefore introduce new alleles into the population. If the cell is somatic then part of the organism will be affected. If the cell is a gamete then the entire offspring will be affected.

26. HOW MUTATIONS OCCUR Mutations can be spontaneous or induced. One in five of us on average carries a new mutant gene! • Most mutations are harmful. • Beneficial ones tend to occur more often in organisms with short generation times.

27. GENE MUTATIONS Mutations that affect one gene arise from point mutations – a change in a single base pair on a DNA strand. They are called Substitution mutations – may change one Amino Acid in the protein Normal DNA Normal polypeptide Mutant DNA mRNA Mutated DNA creates a STOPcodon which prematurely ends synthesis of the polypeptide chain e.g. Sickle cell anaemia

28. frame shiftmutations – stuff up the whole rest of the sequence. - Insertion – extra base is added - Deletion – base is removed Codons read differently so a new sequence of amino acids is added. Mutation: Insertion of C Original DNA Normal polypeptide Large scale frame shift results in a new amino acid sequence. The resulting protein is unlikely to have any biological activity. Mutant DNA mRNA Amino acids

29. THE MONK Who is this dude? How about this one? Gregor Mendel. He is the father of genetics – he is the reason that we can clone sheep, cure diseases and why CSI is on telly. Sort of. Mendel’s work: He spent many years studying pea plants, among other things. He found that they had a large amount of variation in their appearance, and sought to find out why.

30. MENDEL AND PEAS In one of his experiments he took the anthers off a purple flower. Why? To stop it self fertilizing! He then took pollen from a white flower and fertilized the purple flower. He found that 100% of the offspring were purple. He then took two of the purple offspring and crossed them. What do you think he found?

31. THE PEA EXPERIMENT Mendel had no answer for this. No one had studied inheritance this closely before. He deduced that: • Each parent contributes a piece of information to the offspring. • Some information was “dominant” to the other. • Which bits of information the offspring got from it’s parent was controlled by random chance.

32. This is a monohybrid cross All possible combinations of gametes can be shown (father can roll TT, mother can’t tt) The genotype of all offspring can be worked out Can work out the chances or ratio of any combination occurring in this case: Genotype 100% Tt Phenotype 100% Can roll Punnet Square Fathers sperm T T Mothers egg Tt Tt t Tt Tt t

33. What are the Genotypes of children? What are the phenotypes? Roller, non roller What is the ratio of phenotypes? 3:1 How can we tell if the genotype of a tongue roller is TT or Tt? Punnet Square Fathers sperm T t Mothers egg TT Tt T Tt tt t

34. GENETICS PROBLEMS In humans, blue eyes are recessive to brown: Dad (Blue eyes) Mum (Brown eyes) Baby (Blue eyes) Is Mum homozygous for brown eyes? ________ How do you know? (complete the Punnett square)

35. MICE In mice, albino is a recessive trait Stuart Little Big Momma mouse Poppa mouse Complete the Punnett square to show how Stuart ended up an albino If there were 8 babies in the litter, how many would we expect to have normal colouring? _________

36. LABRADORS In Labs, black is the dominant trait The pups are all black These 2 are mated What is the genotype of the pups? _____________ The pups grow up and 2 are mated Here are their kids… Show how this came about (draw the Punnett square) What percentage would we expect to have golden colouring? ____________

37. Test / Back Cross • Shows the genotype of an unknown • Eg. Dominant phenotype - Purple flower • Genotype could be Pp or PP • Cross with homozygous recessive (Pure Breeding) e.g. pp phenotype white • 2 results All purple so genotype is PP Half purple so genotype is Pp

38. DISCRETE HUMANCHARACTERISTICS Discrete is “not continuous” – it must be one of a few possibilities.

39. Pedigree Diagrams • Method for studying the inheritance of genes • Male • Female • Affected male • Mating

40. Pedigree Diagrams • Genotype inside, Phenotype under rr Rr Curly Straight rr Rr Rr Curly Straight Straight

41. Pedigree Chart 1. Is this trait recessive or dominant? Explain. 2. Explain why generation IV has two affected members, while generation II has only one.

42. Animal/ plant breeding Genetic engineering Cloning Application of Genetics

43. Humans select desired traits Over generations all offspring show traits Selective breeding Inbreeding leads to recessive traits showing Animal/Plant selective breeding

44. Hybridisation Crossing different strains New breeds Eg Zonkey Animal / Plant Breeding Blue rose

45. Transfer of genes from one organism to another Good – crop yield, resistance Bad – food chain, crosses species Genetic engineering

46. GENETIC ENGINEERING This tobacco plant has had firefly genes inserted… The human gene for the production of insulin (medicine for diabetics) has been inserted into cows so that insulin comes out with their milk. This has been done with bacteria too. The genes for “roundup” resistance has been put into sweet corn, so we can spray around them easily and not harm the crop. The genes for human ear growth can be inserted on the back of a mouse… Spare parts!

47. Production of genetically identical individuals Plants from cuttings Mammals from single cell Good - high yield, disease resistant, stem cell harvest, transplant tissue, save endangered species! Bad – inefficient (10% success), no variation, die young, super race? Cloning • Clone a mouse!

48. MORE ON CLONING Celebrity Sheep Has Died at Age 6 Dolly, the first mammal to be cloned from adult DNA, was put down by lethal injection Feb. 14, 2003. Prior to her death, Dolly had been suffering from lung cancer and crippling arthritis. Although most Finn Dorset sheep live to be 11 to 12 years of age, postmortem examination of Dolly seemed to indicate that, other than her cancer and arthritis, she appeared to be quite normal. The unnamed sheep from which Dolly was cloned had died several years prior to her creation. Dolly was a mother to six lambs, bred the old-fashioned way. Why NOT clone? Do we understand all the issues? Inefficient – less than 10% of all cloning attempts work. Lack of variation. Ethical issues… • Can you produce a human foetus just to use as spare parts? Something to think about… Plants are cloned all the time. NZ has forests made up entirely of clones. All bananas are cloned (they don’t have seeds do they?) and so are lots of other plants. No one is worried about that. What’s the difference?

49. RANDOM GENETICS QUESTIONS • Compare and contrast the processes of Mitosis and Meiosis. Include the purposes and end products of these. • Explain how sex is determined in humans, and why different families have different numbers of male and female offspring. 3. Define the following terms: Zygote Pure breeding Gamete haploid Allele Diploid Homologous Heterozygous Recessive 4. Explain how 2 brown haired parents can have a blonde child. 5. How many chromosomes are in human cells? 6. Explain the connection between DNA, genes, alleles and chromosomes.

50. http://www.bbc.co.uk/schools/gcsebitesize/biology/variationandinheritance/index.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/biology/variationandinheritance/index.shtml