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UNIT IV Chapter 11 Introduction to Genetics. Introduction to Genetics I. Ancient Concepts of Genetics A. Domestication of Plants and Animals 1. Necessary.

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Presentation on theme: "UNIT IV Chapter 11 Introduction to Genetics. Introduction to Genetics I. Ancient Concepts of Genetics A. Domestication of Plants and Animals 1. Necessary."— Presentation transcript:

1 UNIT IV Chapter 11 Introduction to Genetics

2 Introduction to Genetics I. Ancient Concepts of Genetics A. Domestication of Plants and Animals 1. Necessary step in human societies (going from hunter/gatherer to agriculture and herding) 2. Gradual process 3. Dogs sheep, goats, oxen, horses, camels domesticated 10,000 to 12,000 years ago 4. Cultivated plants developed (date palms, cereal crops, rice, corn) at same time

3 B. ‘Myths and Mutants’ 1. Work with animals led to recognition of heritable traits in humans Heredity- biological inheritance 2. Stories of heritable deformities in humans appear in myths and legends (e.g. cyclops, giants, etc.) a.60 birth defects on Babylonian clay tablets (5000 years ago) b. Knowledge of traits played role in shaping social customs and more (e.g. choosing a wife/husband)

4 C. Early Theories 1. Theory of Blending of Inheritance- e.g. giraffe result of mating of camel with leopard. +=

5 2. Democritus (300 B.C.)- idea that tiny particle (pangenes) controlled inheritance of particular traits. a. Each part of body contained these particles responsible for inheritance of that specific part b. Periodically these particles joined to form sperm and ova.

6 3. Pangenisis- (inheritance of acquired characteristics) theory of Jean Baptiste Lamarck- late 18 th century. Any change in animal or plant after it had been born or sprouted but before it had reproduced was passed onto offspring when it did reproduce. a. Modified ideas of Democritus (inheritance of pangenes) b. Environment could induce changes (e.g. long neck of giraffe, ‘acquired’ large claw of fiddler crab c. Errors quite obvious

7 4. Preformation- 17 th century. Sperm and egg discovered- thought contained miniatures of adults

8 II. The Work of Gregor Mendel A.Gregor Mendel ( ) “Father of Genetics” Genetics- branch of biology that studies heredity 1. Discovered basic principles of heredity- still apply today 2. Conducted carefully planned experiments

9 a. Selected pea plants for study 1). Easy to grow, take little space, easily observable traits 2). Can be self-pollinated or cross-pollinated To cross-pollinate pea plants, Mendel cut off the male parts of one flower and then dusted it with pollen from another flower. The resulting seeds were crosses between the two plants b. Applied math with biology. (analyzed results according to principles of probability and statistics

10 B. Genes and Dominance 1. Mendel studied 7 different pea plant traits trait- specific characteristic, such as seed color or height

11 a. Each trait has contrasting characters (e.g. green seed color or yellow seed color) b. Mendel crossed plants with 7 contrasting characters. c. P (parental) generation- each original generation d. F 1 generation – offspring of P generation (“filial”- Latin word for “son”) e. Hybrids- offspring of crosses between parents with different traits.

12 2. Mendel’s experiments a.First set of experiments- crossed purebred tall plants with purebred short plants Purebred- organism that always produces the same trait in offspring. (homozygous) 1). Offspring (F 1 generation) were all Tall no blending. Short trait seemed to disappear

13 2). From this, Mendel concluded 2 things a). Biological inheritance is determined by factors passed from one generation to the next (we now call genes). Said these occurred in two contrasting forms (e.g. tall/short) different forms called alleles Dominant allele- trait always shows Recessive allele- will only have that form when dominant allele for trait is not present b). Principle of Dominance- States that some alleles are dominant and others are recessive

14 b. Second set of experiments- Mendel wanted to answer the question- “did recessive alleles disappear or were they still present in F 1 plants. 1). Allowed F 1 hybrid plants to produce F 2 by self-pollination

15 2). 25% of offspring showed recessive characteristics 3). Explained as follows: The Principle of Segregation- Mendel said that alleles for tall and short in F 1 plants were separated (segregated) from each other during the formation of sex cells (gametes)

16 III. Probability and Punnett Squares A. Genetics and Probability- Mendel realized principles of probability could be used to explain results of genetic crosses. 1. Probability- likelihood that a particular event will occur. 2. Alleles segregate randomly like a coin flip. 50/50 chance each time.

17 B. Punnett Square- tool used to represent the possible gene combinations from a genetic cross. parent gametes Recessive allele homozygous Possible offspring Dominant Allele heterozygous

18 1. Phenotype- physical characteristics (what they look like. (e.g. tall, short) 2. Genotype- genetic makeup (e.g. TT, Tt, tt) TT tt

19 C. Independent Assortment- Mendel wanted to find out if alleles separated independantly (is the inheritance of one characteristic linked to another. E.g. Must a round seed by yellow?) 1. Two-Factor Cross- Mendel experimented to determine if alleles segregated independently 2. Mendel’s two-factor experimental results were very close to 9:3:3:1 ratio predicted by punnett square. Proved that genes that segregate independently do not influence each other’s inheritance. Principle of Independent Assortment

20 D. Beyond Dominant and Recessive Alleles 1. Incomplete Dominance- one allele is not completely dominant over another (phenotype is a uniform blend, original colors do not show)

21 2. Codominance- similar to incomplete dominance. Both original alleles contribute to phenotype of organism and are shown In certain varities of chickens, black and white feather colors are caused by codominant alleles. Thus the heterozygous phenotype, speckled black and white, is a result of the expression of both alleles

22 3. Multiple Alleles- More than two possible alleles exist for a trait (e.g. blood type, eye color)(deals with one gene)

23 4. Polygenic traits- trait produced by interaction of several genes (e.g. human skin color, height of humans)

24 IV. Meiosis A. Chromosome number 1. Diploid number- means “two sets”. Represented by symbol 2N. One of each set from mother/father. Sets called homologous chromosomes a. Diploid cells found in body cells b. Contains two sets of chromosomes and two sets of genes

25 2. Haploid number- means “one set”. Represented by N. a. Gametes (sex cells) all haploid b. Haploid cells (gametes) produced by meiosis I

26 B. Phases of Meiosis (2 stages) 1. Meiosis I - each chromotid arm is replicated (copied) a. Similar to mitosis- but chromosomes line up in pairs- Tetrads in prophase I b. Exchange of portions of chromatids takes place while chromosomes exist as tetrads. Called crossing-over c. Results in two haploid daughter cells

27 1. Meiosis II - a. replication of chromatids b. Results in four haploid daughter cells C. Gamete formation- in animals: egg and sperm

28 Meiosis and fertilization

29 It’s easy to see how genes located on different chromosomes assort independently, but what about genes located on the same chromosomes? Wouldn’t they generally be inherited together? The answer to these questions, Thomas Hunt Morgan first realized in 1910, is yes !

30 D. Linkage and Gene Maps 1. Gene Linkage- genes on same chromosome almost always inherited together (unless separated by “crossing over” during meiosis) a. Experiments by Thomas Hunt Morgan (1910)- research on fruit flies (Drosophila melanogaster) 1). Chromosomes big, only 4 pair, bred quickly 2). Concluded: chromosomes assort independently, not the individual genes

31 b. By luck, 6 of the 7 genes Mendel studied were on different chromosomes (the two genes found on the same chromosome were so far apart that they also assorted independently- due to crossing over)

32 2. Gene Maps- rate of “crossing over” used to map location of genes on chromosomes a. Alfred Sturtevant- said further apart the genes were, the more likely they were to be separated during crossover in meiosis b. Gathered data and “mapped” location of genes in Drosophila chromosomes c. Also used to map human genome

33 Chapter 11 Introduction to Genetics

34 Gregor Mendel used pea plants to study a.flowering. b.gamete formation. c.the inheritance of traits. d.cross-pollination.

35 Gregor Mendel used pea plants to study a.flowering. b.gamete formation. c.the inheritance of traits. d.cross-pollination.

36 Offspring that result from crosses between true-breeding parents with different traits a.are true-breeding. b.make up the F 2 generation. c.make up the parental generation. d.are called hybrids.

37 Offspring that result from crosses between true-breeding parents with different traits a.are true-breeding. b.make up the F 2 generation. c.make up the parental generation. d.are called hybrids.

38 What are Mendel’s factors called today? a.alleles b.traits c.genes d.characters

39 What are Mendel’s factors called today? a.alleles b.traits c.genes d.characters

40 Mendel concluded that traits are a.not inherited by offspring. b.inherited through the passing of factors from parents to offspring. c.determined by dominant factors only. d.determined by recessive factors only.

41 Mendel concluded that traits are a.not inherited by offspring. b.inherited through the passing of factors from parents to offspring. c.determined by dominant factors only. d.determined by recessive factors only.

42 The principle of dominance states that a.all alleles are dominant. b.all alleles are recessive. c.some alleles are dominant and others are recessive. d.alleles are neither dominant nor recessive.

43 The principle of dominance states that a.all alleles are dominant. b.all alleles are recessive. c.some alleles are dominant and others are recessive. d.alleles are neither dominant nor recessive.

44 When Mendel crossed true-breeding tall plants with true-breeding short plants, all the offspring were tall because a.the allele for tall plants is recessive. b.the allele for short plants is dominant. c.the allele for tall plants is dominant. d.they were true-breeding like their parents.

45 When Mendel crossed true-breeding tall plants with true-breeding short plants, all the offspring were tall because a.the allele for tall plants is recessive. b.the allele for short plants is dominant. c.the allele for tall plants is dominant. d.they were true-breeding like their parents.

46 If a pea plant has a recessive allele for green peas, it will produce a.green peas if it also has a dominant allele for yellow peas. b.both green peas and yellow peas if it also has a dominant allele for yellow peas. c.green peas if it does not also have a dominant allele for yellow peas. d.yellow peas if it does not also have a dominant allele for green peas.

47 If a pea plant has a recessive allele for green peas, it will produce a.green peas if it also has a dominant allele for yellow peas. b.both green peas and yellow peas if it also has a dominant allele for yellow peas. c.green peas if it does not also have a dominant allele for yellow peas. d.yellow peas if it does not also have a dominant allele for green peas.

48 When you flip a coin, what is the probability that it will come up tails? a.1/2 b.1/4 c.1/8 d.1

49 When you flip a coin, what is the probability that it will come up tails? a.1/2 b.1/4 c.1/8 d.1

50 The principles of probability can be used to a.predict the traits of the offspring produced by genetic crosses. b.determine the actual outcomes of genetic crosses. c.predict the traits of the parents used in genetic crosses. d.decide which organisms are best to use in genetic crosses.

51 The principles of probability can be used to a.predict the traits of the offspring produced by genetic crosses. b.determine the actual outcomes of genetic crosses. c.predict the traits of the parents used in genetic crosses. d.decide which organisms are best to use in genetic crosses.

52 Organisms that have two identical alleles for a particular trait are said to be a.hybrid. b.homozygous. c.heterozygous. d.dominant.

53 Organisms that have two identical alleles for a particular trait are said to be a.hybrid. b.homozygous. c.heterozygous. d.dominant.

54 In the Punnett square shown in Figure 11-1, which of the following is true about the offspring resulting from the cross? a.About half are expected to be short. b.All are expected to be short. c.About half are expected to be tall. d.All are expected to be tall.

55 In the Punnett square shown in below, which of the following is true about the offspring resulting from the cross? a.About half are expected to be short. b.All are expected to be short. c.About half are expected to be tall. d.All are expected to be tall.

56 What does a Punnett square NOT show? a.all possible results of a genetic cross b.the genotypes of the offspring c.the alleles in the gametes of each parent d.the actual results of a genetic cross

57 What does a Punnett square NOT show? a.all possible results of a genetic cross b.the genotypes of the offspring c.the alleles in the gametes of each paren d.the actual results of a genetic cross

58 If you made a Punnett square showing Mendel’s cross between true-breeding tall plants with true- breeding short plants, the square would show that the offspring had a.the genotype of one of the parents. b.a phenotype that was different from that of both parents. c.a genotype that was different from that of both parents. d.the genotype of both parents.

59 If you made a Punnett square showing Mendel’s cross between true-breeding tall plants with true- breeding short plants, the square would show that the offspring had a.the genotype of one of the parents. b.a phenotype that was different from that of both parents. c.a genotype that was different from that of both parents. d.the genotype of both parents.

60 What principle states that during gamete formation genes for different traits separate without influencing each other’s inheritance? a.principle of dominance b.principle of independent assortment c.principle of probabilities d.principle of segregation

61 What principle states that during gamete formation genes for different traits separate without influencing each other’s inheritance? a.principle of dominance b.principle of independent assortment c.principle of probabilities d.principle of segregation

62 The Punnett square in Figure above shows that the gene for pea shape and the gene for pea color a.assort independently. b.are linked. c.have the same alleles. d.are always homozygous.

63 The Punnett square in Figure above shows that the gene for pea shape and the gene for pea color a.assort independently. b.are linked. c.have the same alleles. d.are always homozygous.

64 How many different allele combinations would be found in the gametes produced by a pea plant whose genotype was RrYY? a.2 b.4 c.8 d.16

65 How many different allele combinations would be found in the gametes produced by a pea plant whose genotype was RrYY? a.2 b.4 c.8 d.16

66 Situations in which one allele for a gene is not completely dominant over another allele for that gene are called a.multiple alleles. b.incomplete dominance. c.polygenic inheritance. d.multiple genes.

67 Situations in which one allele for a gene is not completely dominant over another allele for that gene are called a.multiple alleles. b.incomplete dominance. c.polygenic inheritance. d.multiple genes.

68 A cross of a red cow with a white bull produces all roan offspring. This type of inheritance is known as a.incomplete dominance. b.polygenic inheritance. c.codominance. d.multiple alleles.

69 A cross of a red cow with a white bull produces all roan (red ) offspring. This type of inheritance is known as a.incomplete dominance. b.polygenic inheritance. c.codominance. d.multiple alleles.

70 A cross of a red cow with a white bull produces all roan (red and white spots) offspring. This type of inheritance is known as a.incomplete dominance. b.polygenic inheritance. c.codominance. d.multiple alleles.

71 A cross of a red cow with a white bull produces all roan offspring. This type of inheritance is known as a.incomplete dominance. b.polygenic inheritance. c.codominance. d.multiple alleles.

72 Mendel’s principles of genetics apply to a.plants only. b.animals only. c.pea plants only. d.all organisms.

73 Mendel’s principles of genetics apply to a.plants only. b.animals only. c.pea plants only. d.all organisms.

74 If an organism’s diploid number is 12, its haploid number is a.12. b.6. c.24. d.3.

75 If an organism’s diploid number is 12, its haploid number is a.12. b.6. c.24. d.3.

76 Gametes are produced by the process of a.mitosis. b.meiosis. c.crossing-over. d.replication.

77 Gametes are produced by the process of a.mitosis. b.meiosis. c.crossing-over. d.replication.

78 What is shown in figure above? a.independent assortment b.b.anaphase I of meiosis c.crossing-over d.replication

79 What is shown in figure above? a.independent assortment b.anaphase I of meiosis c.crossing-over d.replication

80 Unlike mitosis, meiosis results in the formation of a.diploid cells. b.haploid cells. c.2N daughter cells. d.body cells.

81 Unlike mitosis, meiosis results in the formation of a.diploid cells. b.haploid cells. c.2N daughter cells. d.body cells.

82 Linked genes a.are never separated. b.assort independently. c.are on the same chromosome. d.are always recessive.

83 Linked genes a.are never separated. b.assort independently. c.are on the same chromosome. d.are always recessive.

84 If two genes are on the same chromosome and rarely assort independently, a.crossing-over never occurs between the genes. b.crossing-over always occurs between the genes. c.the genes are probably located far apart from each other. d.the genes are probably located close to each other.

85 If two genes are on the same chromosome and rarely assort independently, a.crossing-over never occurs between the genes. b.crossing-over always occurs between the genes. c.the genes are probably located far apart from each other. d.the genes are probably located close to each other.


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