Biology Form 5 Chapter 6 Variation 6.1
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Biology Form 5 Chapter 6 Variation
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Biology Form 5 Chapter 6 Variation 6.1
- 1. The same but different ! Variation
- 2. AREN’T GOD’S CREATIONS AMAZING?
- 4. The DNA Between Individuals is Identical. All differences are in the 0.1% of DNA that varies. A C C G T C C A G G A C C G T G C A G G It’s hard to believe sometimes!
- 5. Why aren’t fruits from the same plant identical ?
- 6. So why are Identical twins not identical ? Twins have identical genes in their bodies……. Yet they do not have identical characteristics.
- 7. What is a species? A group of organisms which can reproduce Examples? The differences within a species are called variation Variation is difference in traits in organisms of the same species
- 8. VARIATION
- 11. Variation In Humans Unattached ear lobes are inherited as a dominant trait. Attached ear lobes are inherited as a recessive trait.
- 12. Variation In Humans Having a bent little finger is a dominant trait
- 15. Skin colour
- 18. You got half of your chromosomes from your mum and half from your dad Who did you inherit you eye colour from? Nose shape? Hair colour? Where did you get your chromosomes from?Where did you get your chromosomes from?
- 19. Cause of Variation 1. Genes (inherited) 2. Environment. 3. Interaction between genes and the environment. Examples?
- 22. Variation Differences in characteristics shown by organisms of the same species two types of variation: DISCONTINUOUS CONTINUOUS
- 23. Discontinuous Variation Produces: individuals with clear-cut differences with no intermediates between them examples: blood group in humans sex tongue rolling Either OR traits Either OR traits
- 24. Eye colour in 9K 0 1 2 3 4 5 6 7 8 blue green hazel brown grey black Frequency DISCRETE DISTRIBUTION Discontinuous Variation
- 25. The environment cannot change discontinuous type of variations No matter how much you stay in the sun orNo matter how much you stay in the sun or what you eat – will not change your bloodwhat you eat – will not change your blood group!!group!!
- 26. Continuous Variation characteristic varies amongst the members of a species in a smooth continuous way from one extreme to the other
- 27. Continuous variation is affected by: 1.many genes 2.AND the environment
- 28. The environment CAN change these variations Sun bathing causes tanning of skin. Eating carrots makes human skin and feathers in birds turn orange.
- 29. Continuous Variation: Examples: Mass Height Intelligence Colour of organs & organisms
- 31. Differences between Continuous & Discontinuous Variation Continuous Discontinuos Is controlled by many pairs of alleles Is controlled by a single pair of alleles Caused by genetic / environmental factors or both. (only genetic factors inherited) Caused by genetic factors only Normal distribution Discrete distribution Eg. Height, skin colour, Intelligence, body weight. Eg. Blood group, ability to roll tongue, fingerprint, colour blindness. Eye colour in 9K 0 1 2 3 4 5 6 7 8 blue green hazel brown grey black Frequency
- 32. How does variation come about? #Environmental factor #Genetic factor Sexual reproduction Mutations
- 33. Genetic Factor that cause variation GENETIC MUTATION SEXUAL REPRODUCTION CHROMOSOMAL MUTATION GENE MUTATION INDEPENDENT ASSORTMENT CROSSING OVER RANDOM FERTILISATION duplication inversion translocation deletion deletion insertion substitution
- 34. Offspring of sexual reproduction are highly varied The Origins of Genetic Variation Sexual Reproduction
- 35. What about this wheat grown in the same field from the same parent plants ?
- 36. Genetic Factor that cause variation GENETIC MUTATION SEXUAL REPRODUCTION CHROMOSOMAL MUTATION GENE MUTATION INDEPENDENT ASSORTMENT CROSSING OVER RANDOM FERTILISATION duplication inversion translocation deletion deletion insertion substitution
- 37. Crossing-over between chromatidsCrossing-over between chromatids during meiosis 1 (Prophase 1)during meiosis 1 (Prophase 1) Based on: Mader, S., Inquiry Into Life, McGraw-Hill
- 38. Crossing Over – Homologous chromosomes exchange genetic information during Prophase I meiosis – Genetic recombination occurs – more genetic diversity to gametes Figure 8.18 Prophase I of meiosis Metaphase I Metaphase II Gametes Recombinant chromosomes Spindle microtubules Tetrad Chiasma, site of crossing Over (remain attached to e/o at chiasmata until Anaphase I) Homologs are closely paired
- 39. Genetic Factor that cause variation GENETIC MUTATION SEXUAL REPRODUCTION CHROMOSOMAL MUTATION GENE MUTATION INDEPENDENT ASSORTMENT CROSSING OVER RANDOM FERTILISATION duplication inversion translocation deletion deletion insertion substitution
- 40. The orientation of the homologous pairs of chromosomes (tetrads) at metaphase I is a matter of chance, each has 2 possible ways they can line up. Independent Assortment of Chromosomes Figure 8.17 Possibility 1 Metaphase of meiosis II Combination a Combination b Combination c Combination d Gametes Possibility 2 Metaphase of meiosis I MEIOSIS
- 41. ……chromosomes can line upchromosomes can line up 222323 or 10 million (10or 10 million (1077 )) different waysdifferent ways in meiosis Iin meiosis I ……so each person can produceso each person can produce 10 million (or 1010 million (or 1077 ) different types) different types of gametesof gametes During meiosis in humans…During meiosis in humans…
- 42. Meiosis – homologous chromosomes separate independently from each other and pass into a different gamete ( INDEPENDENT ASSORTMENT). – a great variety of gametes are produced Causes of VariationsCauses of Variations
- 43. Genetic Factor that cause variation GENETIC MUTATION SEXUAL REPRODUCTION CHROMOSOMAL MUTATION GENE MUTATION INDEPENDENT ASSORTMENT CROSSING OVER RANDOM FERTILISATION duplication inversion translocation deletion deletion insertion substitution
- 44. For each couple…For each couple… 101077 types of spermtypes of sperm xx 101077 types of eggstypes of eggs 10101414 types of childrentypes of children
- 45. ~~ENDEND~~ END OF PART 1 GO TO 6.2
- 46. EXTRA
- 47. Question: SEP, 2005 [pg. 83] Look at the drawings of the two men. List two features shown in the diagram, that are inherited and three features that are not inherited. (5)
- 48. Types of VariationsTypes of Variations 2.Discontinuous Variation – the characteris clear-cut & not showing intermediates – eg. tongue rolling, earlobes and colourof corn albinism Eye colour in 9K 0 1 2 3 4 5 6 7 8 blue green hazel brown grey black Frequency DISCRETE DISTRIBUTION
- 50. Environmental variations cannot be inherited
- 52. XXY males Tall High testosterone Severe acne More predisposed to criminal activities and behavioural problems
- 53. Poliploidy Chromosomal Mutation Polyploid organisms: − Triploids (3n) – three sets of chromosomes of one type − Tetraploid (4n) – have four sets of chromosomes Polyploidy is common in flowering plants Not occuring in animals Produce bigger fruit with more
- 54. Duplication a b c d e f g a b c d e d e f g Occurs when a broken segment of a chromosomes joins with the other chromosomes of the homologous pair
- 55. a b c d e f g a b c d e f g a b c d e f g a b c d e q r a b c d e f g a b c d e f g l m n o p q r a b c d e f g a b c d e f g l m n o p f g Translocation Occurs when a segment of a chromosome breaks off and joins a non homologous chromosomes
- 56. a b c d e f g a b c d f g Deletion Occurs when one end of a chromosome or an internal segment breaks off the two rejoin to form a chromosome defecient gene
- 57. a b c d e f g a b c d f e g Break Inversion Occurs when a segment of a chromosome breaks loose, rotates 180 and rejoin in reverse direction - lead to altered gene activity
Editor's Notes
- Note that this activity may raise some discussion, as some of the features are of course affected by both genetics and environment. The answers for this activity have been worked out on the most simple scenario. See the following two slides for a discussion of the more real but a bit more complicated situation.
- Main Idea(s) of This Slide - During the process of meiosis some homologous chromosomes “trade” portions of their DNA with each other resulting in new configurations of alleles.
- Main Idea(s) of This Slide - The 23 pairs of chromosomes found in human cells can line up in 10 million different ways during the first phase of meiosis. Because of this, each person is capable of producing 10 million genetically unique gametes.
- Main Idea(s) of This Slide - In one couple, the man can produce 10 million (107) genetically different sperm cells and the woman can produce 10 million (107) genetically different egg cells. By randomly combining one of each, we end up with a possible 1014 genetically different offspring that can be produced.