Genetics and Variation - A Revision Slideshow

1. Revision Slideshow for Midterm Exam REVISION DSRU EP M3

2. Types of Variation People are similar, but not identical, to their parents or each other. The differences in a species are called variation. Variation can come about for two reasons. What are they? 1. People inherit characteristics from both of their parents and each person gets a different combination of features. This is called inherited variation. 2. Other characteristics are affected a person’ surroundings. This called environmental variation. Which features are environmental and which are inherited?

3. Quiz Click the Quiz button to edit this quiz

4. Genetics 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. Genetics Problems 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?

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

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

11. Genetics Problems Example 3: A heterozygous brown-eyed father and a blue-eyed mother: Father Mother

12. Genetics Problems In rabbits, assume that the dominant allele (B) produces black fur. The allele (b) for white fur is recessive to B. (a) What colour fur will each of the following rabbits have? Rabbit 1 Rabbit 2 Rabbit 3 Rabbit 4 genotype BB Bb bBbb (b) Which rabbits are homozygous for coat colour? (c) If rabbits 1 and 4 were mated together and had 12 babies, how many of these would you expect to be black? (d) If rabbits 2 and 3 are interbred and produce several litters, totalling 48 babies, how many white babies would be predicted by the laws of genetics?

13. X Ff Ff X Cc cc X Ss Ss Inherited Diseases 1) Cystic fibrosis – a disease that causes thick and sticky mucus to coat the lungs, gut and pancreas. It’s caused by recessive alleles: 2) Huntingdon's disease – a disease of the nervous system that causes shaking and eventually dementia. It’s caused by a dominant allele: 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:

14. Artificial Animal Cloning • Artificial cloning of animals is now commonplace in laboratories. • The most famous example of animal cloning is Dolly the Sheep, born in the UK in 1996 using a technique called cell transferring.  

15. Artificial Animal Cloning • An egg cell was removed from the ovary of an adult female sheep, and the nucleus removed. • Using micro-surgical techniques, the empty egg cell was fused with DNA extracted from an udder cell of a donor sheep • The fused cell now began to develop normally, using the donated DNA. • Before the dividing cells became specialised the embryo was implanted into the uterus of a foster-mother sheep.

16. Artificial Animal Cloning

17. Advantages of Cell Transferring • Allows screening for defects in gametes. • Makes it possible to choose sex and time of birth. • Exact copies of the 'best' animal specimens, year after year. • Could be used for saving endangered species from extinction.

18. Disadvantages of Cell Transferring • Does not add variety - so no opportunity for natural selection. • Lack of hybrid vigour - animals potentially vulnerable to disease. • Danger of reducing the gene pool. • Some animal welfare concerns - eg about the longevity of cloned animals.

19. Genetic Engineering • Genetic engineering (also known as genetic manipulation or GM is not the same as cloning.

20. Genetic Engineering • In the past, humans have brought about change in the genetic make-up of organisms by means of selected breeding. Genetic engineering brings about such change by scientifically altering an organism's genetic code. • In genetic engineering enzymes are used to cut up and join together parts of the DNA of one organism, and insert them into the DNA of another organism. In the resulting new organism the inserted genes will code for one or more new characteristics.

21. Genetic Engineering

22. Applications of Genetic Engineering • One field in which genetic engineering has had a huge impact is the mass production of insulin to help diabetics. • Scientists have isolated the gene responsible for making human proteins, including the insulin hormone. • This gene is inserted into the bacterial DNA, and the microbes then clone themselves rapidly, making identical copies of themselves, all with the new gene and all capable of making human insulin.

23. Applications of Genetic Engineering • Producing human growth hormone to treat growth abnormalities. • Blood clotting factor to treat haemophiliacs. • Used in industry to produce enzymes for use in biological washing powder. • Producing pest resistant crop varieties. • Producing tomatoes that stay fresh much longer.

24. The Human Genome Project • The genetic information in an organism is called its genome. The Human Genome Project, or HGP for short, was started at the end of the last century. It was very ambitious and had several aims, including:   • to work out the order or sequence of all the three billion base pairs in the human genome • to identify all the genes • to develop faster methods for sequencing DNA.

25. DNA Fingerprinting • Information about a person's DNA can be useful for forensic science. Genetic fingerprinting was invented in 1985 by Sir Alec Jeffreys at the University of Leicester. • It uses some of the small differences between the DNA from different people to make a picture rather like a barcode.

26. DNA Fingerprinting • If enough parts of the DNA are tested, it is very unlikely that two identical DNA fingerprints would belong to two different people. • This makes the method very useful for matching samples found at the scene of a crime to people suspected of committing the crime.  

27. Competition Competition is one of the factors that affects population sizes. What type of organisms compete for resources? Competition occurs between different species…

28. Competition Members of the same species also compete for resources. Why do living things need to compete and what do they compete for?

29. Competition What four things do animals in the same species or animals of different species have to compete for? food water space mates

30. Literal definition:the act of living together Symbiosis What it means: Two organisms that live together Temporarily or for a longer time At least one of the organisms benefits from the relationship

31. Symbiosis Commensalism Mutualism both organisms benefit one organism benefits one organism benefits Parasitism one organism is unaffected one organism is harmed

32. Moray Eel with Cleaner Fish Examples of Symbiosis Moray Eel gets a clean mouth Cleaner Fish gets a meal

33. Cattle with cattle egrets Cattle stir up insects as they eat grassEgrets hang around and eat insects Examples of Symbiosis Commensalism: one benefits, one is unaffected

34. Clown fish with anemone Clown fish gets protection Anemone is unaffected Examples of Symbiosis Commensalism: one benefits, one is unaffected

35. Biological Control Biological control is the use of parasites, predators or pathogens (disease-causing organisms) to help control pests ranging from nematodes to weeds to vertebrates.

36. Advantages of Biological Control • It can be cheaper. • There are no concerns about using too much and damaging the environment. • You can be specific about which things you kill, rather than just killing every insect including the useful ones. • You can sell edible plants and crops without having to worry about pesticide residues inside them.

37. Advantages of Biological Control The only disadvantage is that you never get rid of all the pests but instead after a couple of years the number of pests will have fallen to an acceptable, lower level. The following diagram illustrates what happens when a pest is controlled by using a predator against it:

38. Local Examples of Biological Control • Parasitic Wasps used to kill mealybugs in cassava plantations. • Using Fish to kill mosquito larvae.

39. The arrows show which way the energy is going in the chain Food Chains A food chain shows what is eaten by what…

40. Food Chains • Food chains are diagrams that show which animals eat each other • In habitats all animals and plants depend on each other • If one animal dies out it might affect the other animals

41. Food Chains Key Words • Herbivore • Eats only plants • Omnivore • Eats plants AND animals • Carnivore • Eats only animals

42. Food Chains Key Words Secondary Consumer • Gains energy by eating primary consumers. • Usually carnivores but can be omnivores Primary Consumer • Gains energy by eating producers. • Usually herbivores Human Cow Grass Producer • Makes food from sun using photosynthesis

43. Food Webs Food webs contain many interlinking food chains…

44. What would happen if an animal or organism was “taken out”? Food Webs e.g take out the crab: • What would happen to the population of flat winkles? • What would happen to the population of herring gulls? It would increase, because they are not getting eaten as much It would decrease, because there is not as much food

45. Pyramids of Numbers A pyramid of numbers shows how many animals or organisms we are talking about. For example, consider the following food chain:

46. Pyramids of Numbers A pyramid of numbers for this food chain would look like this: One owl Some voles Lots of grass

47. Pyramids of Numbers Consider the food chain: Grass Rabbit FoxFleas Lots of fleas One fox Some rabbits Lots of grass

48. Pyramids of Biomass A pyramid of biomass shows how much the creatures at each level would weigh. Consider the same food chain: Grass Rabbit Fox Fleas

49. Pyramids of Biomass Grass Rabbit Fox Fleas Pyramid of numbers: Pyramid of biomass: