Genetics

1. Genetics Chapter 09

2. Do Now • Think about your favorite type of Dog. If evolution is truly survival of the fittest, how is it your favorite type of dog exists today?

3. 0 Introduction: Barking Up the Genetic Tree • Dogs are one of man’s longest genetics experiments • Dog breeds are the result of artificial selection • Populations of dogs became isolated from each other • Humans chose dogs with specific traits for breeding • Each breed has physical and behavioral traits due to a unique genetic makeup • Sequencing of the dog’s genome shows evolutionary relationships between breeds

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5. 0 Wolf Chinese Shar-Pei Ancestral canine Akita Siberian Husky Alaskan Malamute Basenji Afghan hound Saluki Rottweiler Breeding for traits is as old as agriculture. It didn’t become a science until Gregor Mendel. Sheepdog Retriever

6. Essential Question • Why do we have our specific traits? • Why are they different from our friends, parents and relatives.

7. Mendel’s Experiments • Every living thing—plant or animal, microbe or human being—has a set of characteristics inherited from its parent or parents. • The delivery of characteristics from parent to offspring is called heredity. • The scientific study of heredity, known as genetics, is the key to understanding what makes each organism unique.

8. Who was Gregor Mendel • The founder of modern genetics was an Austrianmonk named Gregor Mendel. • Mendel was in charge of the monastery garden, where he conducted research on garden peas.

9. Austria Not Australia!!! G’day Mate!

10. Mendel • Gregor Mendel discovered principles of genetics in experiments with garden pea plants • Mendel showed that parents pass heritable factors to offspring • What do we call heritable factors today? • Genes

11. Mendel • Advantages of using pea plants • Easily controlledmatings • Self-fertilization or cross-fertilization • Observablecharacteristics with two distinct forms • True-breeding strains • A model system is convenient to study and may transfer to other organisms, including humans, actually function. • Why not just study heredity in humans?

12. The Role of Fertilization • Mendel knew that • the male part of each flower produces pollen, (containing sperm). • the female part of the same flower produces egg cells.

13. The Role of Fertilization • Pea flowers are “True Breeding” aka self-pollinating aka self-fertilizing. • Sperm cells in pollenfertilize the egg cells in the same flower. • The seeds that are produced by self-pollination inherit all of their characteristics from the single plantthat bore them. • Any organism that receives the same genetic traits from both its parents is called purebread. • True Breeding plants have the same traits as their parents

14. True Breeding plants have the same traits as their parents • Traits are specific characteristic of an individual that can be passed from parent to offspring. • Seed color • Plant height • May vary from one individual to another. • So a white flowering plant that self-fertilizes will create more white-flowered plants.

15. The Role of Fertilization • Mendel wanted to produce seeds by joining male and female reproductive cells from two different plants. • He cut away the pollen-bearing male parts of the plant and dusted the plant’s flower with pollen from another plant.

16. The Role of Fertilization • This process is called cross-pollination. • The offspring of crosses between parents with different traits are called hybrids.

17. 0 White Removed stamens from purple flower 1 Stamens Carpel Transferred pollen from stamens of white flower to carpel of purple flower 2 Parents (P) Purple

18. 0 White Removed stamens from purple flower 1 Stamens Carpel Transferred pollen from stamens of white flower to carpel of purple flower 2 Parents (P) Purple Pollinated carpel matured into pod 3

19. 0 White Removed stamens from purple flower 1 Stamens Carpel Transferred pollen from stamens of white flower to carpel of purple flower 2 Parents (P) Purple Pollinated carpel matured into pod 3 Planted seeds from pod 4 Offspring (F1)

20. 0 The 7 traits Mendel Studied were: Flower color Purple White Flower position Axial Terminal Seed color Green Yellow Seed shape Wrinkled Round Pod shape Inflated Constricted Green Pod color Yellow Tall Stem length Dwarf

21. Terms to Know before moving on: • Genes: Genetic information that codes for specific traits. Genes have specific loci on a chromosome. • Diploid (2n)/haploid (n) • True-breeding: Inherit identical alleles generation after generation • Hybrid: Offspring of a cross that has inherited a pair of nonidentical alleles for a trait. • Homozygous: Identical pair of Alleles (TT or tt) • Heterozygous: Pair of differentalleles for a gene (one allele to be tall (T) and one to be short (t)

22. Terms to Know before moving on: • Dominant alleles are allele that will mask any recessive allele for the same trait. • Dominant alleles are represented with a capital letter (tall = T) • Recessive alleles are represented with a lowercase letter (short = t) • Genotype refers to an individual’s particular genes. • Phenotype refers to the individual’s observable or physical traits.

23. 0 Gene loci Dominant allele B a P b P a Recessive allele Bb PP Genotype: aa Homozygous for the recessive allele Heterozygous Homozygous for the dominant allele

24. Try this: • T=tall t=short • A pea plant has the genotype Tt. • Which trait is dominant? Which is recessive? • What is the individual’s phenotype? • Could this plant be a true bred plant?

25. So now we know… • Mendel was an Austrian monk who worked with pea plants. • He wanted to observe how traits were passed on so he cross pollinated plants with contrasting characteristics. • So what did Mendel find?

26. Genes & Alleles • In genetic crosses: • Each original pair of plants is the P (parental) generation. • The offspring are called the F1, or “first filial,” generation.

27. Genes & Alleles • The F1 hybrid plants all had the character of only one of the parents. • In each cross the other parent’s trait seemed to have disappeared

28. Genes & Alleles Mendel’s F1 Crosses on Pea Plants

29. Genes & Alleles Mendel’s F1 Crosses on Pea Plants

30. Genes & Alleles • Mendel's first conclusion was that biological inheritance is determined by factors that are passed from one generation to the next. • Today, scientists call the factors that determine traits genes.

31. Genes and Alleles • Genes are sections of a chromosome that code for a trait. • Most organisms have two copies of every gene and chromosome, one from each parent.

32. Genes and Alleles • Each of the traits Mendel studied was controlled by one gene that occurred in two contrastingforms that produced different characters for each trait. • The different forms of a gene are called alleles. • Certain alleles can hide or dominate over other alleles.

33. Genes and Dominance • Mendel’s second conclusion is called the principle of dominance.

34. Genes and Dominance • The principle of dominance states that some alleles are dominant and others are recessive.

35. Genes and Dominance • An organism with a dominant allele for a trait will always exhibit that form of the trait. • An organism with the recessive allele for a trait will exhibit that form only when the dominant allele for that trait is not present. • A dominant allele will mask a recessive allele

36. Dominant & Recessive Genes • In Mendel’s experiments, • the allele for Tall plants (T) was dominant and the allele for short plants (t) was recessive.

37. Genes and Dominance green Yellow A pea plant has 2 possible alleles for pea color, green and yellow. If the plant has two green alleles, the plant is ___________. If the plant has two yellow alleles, the plant is _____________. If the plant has one yellow & one green allele, the plant is yellow. Which of the two possible alleles is dominant? Which is recessive? Why?

38. Mendel’s experiment did not stop with the F1 generation. 11.2 Mendel’s theory of segregation

39. Before we move on • We need to learn how to make a Punnett-square to help predict possible offspring.

40. How To Make a Punnett Square for a One-Factor Cross • Write the genotypes of the two organisms that will serve as parents in a cross. • In this example we will cross a male and female osprey that are heterozygous for large beaks. They each have genotypes of Bb. • Bb and Bb

42. How To Make a Punnett Square • Determine what alleles would be found in all of the possible gametes that each parent could produce. Male OspreyFemale Osprey Bb x Bb B b B b

43. Draw a table with enough spaces for each pair of gametes from each parent. Enter the genotypes of the gametes produced by both parents on the top and left sides of the table. How To Make a Punnett Square B b B b

44. How To Make a Punnett Square Fill in the table by combining the gametes’ genotypes. B b B b b b

45. How To Make a Punnett Square Fill in the table by combining the gametes’ genotypes. B b B b B b b b

46. How To Make a Punnett Square Fill in the table by combining the gametes’ genotypes. B b B b B b b b B b

47. How To Make a Punnett Square Fill in the table by combining the gametes’ genotypes. B b B b B b B B b b B b

48. How To Make a Punnett Square • Determine the genotypes and phenotypes of each offspring. • Calculate the percentage of each. • In this example, three fourths of the chicks will have large beaks, but only one in two will be heterozygous. B b B b B B B b B b b b

49. Segregation How are different forms of a gene distributed to offspring? • Law of Segregation: During gamete formation, the alleles for each gene segregate (separate) from each other, so that each gamete carries only one allele for each gene.

50. Genetic makeup (alleles) 0 P plants PP pp PP pp Gametes All All p P F1 plants (hybrids) All Pp Pp p P 1 – 2 1 – 2 Gametes Sperm p P P PP Pp F2 plants Phenotypic ratio 3 purple : 1 white Eggs Genotypic ratio 1 PP : 2 Pp : 1 pp Pp pp p