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Chapter 10: Genetics: Mendel and Beyond CHAPTER 10 Genetics: Mendel and Beyond.

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Presentation on theme: "Chapter 10: Genetics: Mendel and Beyond CHAPTER 10 Genetics: Mendel and Beyond."— Presentation transcript:

1 Chapter 10: Genetics: Mendel and Beyond CHAPTER 10 Genetics: Mendel and Beyond

2 Chapter 10: Genetics: Mendel and Beyond The Foundations of Genetics The Foundations of Genetics Mendel’s Experiments and Laws of Inheritance Mendel’s Experiments and Laws of Inheritance Alleles and Their Interactions Alleles and Their Interactions Gene Interactions Gene Interactions

3 Chapter 10: Genetics: Mendel and Beyond Genes and Chromosomes Genes and Chromosomes Sex Determination and Sex-Linked Inheritance Sex Determination and Sex-Linked Inheritance Non-Nuclear Inheritance Non-Nuclear Inheritance

4 Chapter 10: Genetics: Mendel and Beyond The Foundations of Genetics It has long been known that both parent plants contribute equally to character traits of offspringIt has long been known that both parent plants contribute equally to character traits of offspring Before Mendel’s time it was believed that once brought together, the units of inheritance blended and could never be separated.Before Mendel’s time it was believed that once brought together, the units of inheritance blended and could never be separated.4

5 Chapter 10: Genetics: Mendel and Beyond Figure 10.1 figure jpg

6 Chapter 10: Genetics: Mendel and Beyond The Foundations of Genetics Although Gregor Mendel’s work was meticulous and well documented, his discoveries, reported in the 1860s, lay dormant until decades later.Although Gregor Mendel’s work was meticulous and well documented, his discoveries, reported in the 1860s, lay dormant until decades later.6

7 Chapter 10: Genetics: Mendel and Beyond Mendel’s Experiments and Laws of Inheritance Mendel used garden pea plants for his studies because they were easily cultivated and crossedMendel used garden pea plants for his studies because they were easily cultivated and crossed They showed numerous characters with clearly different traits.They showed numerous characters with clearly different traits. Review Figure 10.1, Table

8 Chapter 10: Genetics: Mendel and Beyond Figure 10.1 figure jpg

9 Chapter 10: Genetics: Mendel and Beyond Table 10.1 table jpg

10 Chapter 10: Genetics: Mendel and Beyond Mendel’s Experiments and Laws of Inheritance In a monohybrid cross, the offspring showed one of the two traits.In a monohybrid cross, the offspring showed one of the two traits. Mendel proposed that the trait observed in the first generation (F 1 ) was dominant and the other was recessive.Mendel proposed that the trait observed in the first generation (F 1 ) was dominant and the other was recessive. This is Mendel’s first law.This is Mendel’s first law. Review Table

11 Chapter 10: Genetics: Mendel and Beyond Mendel’s Experiments and Laws of Inheritance When the F 1 offspring were self-pollinated, the F 2 generation showed a 3:1 phenotypic ratio, with the recessive phenotype present in one-fourth of the offspring.When the F 1 offspring were self-pollinated, the F 2 generation showed a 3:1 phenotypic ratio, with the recessive phenotype present in one-fourth of the offspring. Reappearance of the recessive phenotype refuted the blending hypothesis.Reappearance of the recessive phenotype refuted the blending hypothesis. Review Figure 10.3 Review Figure

12 Chapter 10: Genetics: Mendel and Beyond Figure 10.3 figure jpg

13 Chapter 10: Genetics: Mendel and Beyond Mendel’s Experiments and Laws of Inheritance Because some alleles are dominant and some are recessive, the same phenotype can result from different genotypes.Because some alleles are dominant and some are recessive, the same phenotype can result from different genotypes. Homozygous genotypes have two copies of the same allele; heterozygous genotypes have two different alleles.Homozygous genotypes have two copies of the same allele; heterozygous genotypes have two different alleles. Heterozygous genotypes yield phenotypes showing the dominant trait.Heterozygous genotypes yield phenotypes showing the dominant trait.12

14 Chapter 10: Genetics: Mendel and Beyond Mendel’s Experiments and Laws of Inheritance After many crosses, Mendel proposed his second law:After many crosses, Mendel proposed his second law:  the units of inheritance (genes) are particulate  there are two copies (alleles) of each gene in every parent  during gamete formation the two alleles for a character segregate from each other. Review Figure

15 Chapter 10: Genetics: Mendel and Beyond Figure 10.4 figure jpg

16 Chapter 10: Genetics: Mendel and Beyond Mendel’s Experiments and Laws of Inheritance Geneticists who followed Mendel showed that genes are carried on chromosomes and that alleles are segregated during meiosis I.Geneticists who followed Mendel showed that genes are carried on chromosomes and that alleles are segregated during meiosis I. Review Figure

17 Chapter 10: Genetics: Mendel and Beyond Figure 10.5 figure jpg

18 Chapter 10: Genetics: Mendel and Beyond Mendel’s Experiments and Laws of Inheritance Using a test cross, Mendel was able to determine whether a plant showing the dominant phenotype was homozygous or heterozygous.Using a test cross, Mendel was able to determine whether a plant showing the dominant phenotype was homozygous or heterozygous. The appearance of the recessive phenotype in half of the offspring indicates that the parent is heterozygous.The appearance of the recessive phenotype in half of the offspring indicates that the parent is heterozygous. Review Figure

19 Chapter 10: Genetics: Mendel and Beyond Figure 10.6 figure jpg

20 Chapter 10: Genetics: Mendel and Beyond Mendel’s Experiments and Laws of Inheritance From studies of the simultaneous inheritance of two characters, Mendel concluded that alleles of different genes assort independently.From studies of the simultaneous inheritance of two characters, Mendel concluded that alleles of different genes assort independently. Review Figures 10.7,

21 Chapter 10: Genetics: Mendel and Beyond Figure 10.7 figure jpg

22 Chapter 10: Genetics: Mendel and Beyond Figure 10.8 figure jpg

23 Chapter 10: Genetics: Mendel and Beyond Mendel’s Experiments and Laws of Inheritance We can predict the results of hybrid crosses by using a Punnett square or by calculating probabilities.We can predict the results of hybrid crosses by using a Punnett square or by calculating probabilities. To determine the joint probability of independent events, individual probabilities are multiplied.To determine the joint probability of independent events, individual probabilities are multiplied. To determine the probability of an event that can occur in two or more different ways, they are added.To determine the probability of an event that can occur in two or more different ways, they are added. Review Figure

24 Chapter 10: Genetics: Mendel and Beyond Figure 10.9 figure jpg

25 Chapter 10: Genetics: Mendel and Beyond Mendel’s Experiments and Laws of Inheritance That humans exhibit Mendelian inheritance can be inferred by the analysis of pedigrees.That humans exhibit Mendelian inheritance can be inferred by the analysis of pedigrees. Review Figures 10.10,

26 Chapter 10: Genetics: Mendel and Beyond Figure figure jpg

27 Chapter 10: Genetics: Mendel and Beyond Figure figure jpg

28 Chapter 10: Genetics: Mendel and Beyond Alleles and Their Interactions New alleles arise by mutation, and many genes have multiple alleles.New alleles arise by mutation, and many genes have multiple alleles.27

29 Chapter 10: Genetics: Mendel and Beyond Figure figure jpg

30 Chapter 10: Genetics: Mendel and Beyond Alleles and Their Interactions Dominance is usually not complete, since both alleles in a heterozygous organism may be expressed in the phenotype.Dominance is usually not complete, since both alleles in a heterozygous organism may be expressed in the phenotype. Review Figures 10.13,

31 Chapter 10: Genetics: Mendel and Beyond Figure figure jpg

32 Chapter 10: Genetics: Mendel and Beyond Gene Interactions In epistasis, the products of different genes interact to produce a phenotype.In epistasis, the products of different genes interact to produce a phenotype.31

33 Chapter 10: Genetics: Mendel and Beyond Gene Interactions In some cases, the phenotype is the result of the additive effects of several genes (polygenes), and inheritance is quantitative.In some cases, the phenotype is the result of the additive effects of several genes (polygenes), and inheritance is quantitative. Review Figure

34 Chapter 10: Genetics: Mendel and Beyond Figure figure jpg

35 Chapter 10: Genetics: Mendel and Beyond Gene Interactions Environmental variables such as temperature, nutrition, and light affect gene action.Environmental variables such as temperature, nutrition, and light affect gene action.34

36 Chapter 10: Genetics: Mendel and Beyond Genes and Chromosomes Each chromosome carries many genes.Each chromosome carries many genes. Genes located on the same chromosome are said to be linked, and are often inherited together.Genes located on the same chromosome are said to be linked, and are often inherited together. Review Figures 10.19,

37 Chapter 10: Genetics: Mendel and Beyond Figure figure jpg

38 Chapter 10: Genetics: Mendel and Beyond Figure figure jpg

39 Chapter 10: Genetics: Mendel and Beyond Genes and Chromosomes Linked genes recombine by crossing over in prophase I of meiosis, resulting in recombinant gametes, which have new combinations of linked genes.Linked genes recombine by crossing over in prophase I of meiosis, resulting in recombinant gametes, which have new combinations of linked genes. Review Figures 10.21,

40 Chapter 10: Genetics: Mendel and Beyond Figure – Part 1 figure 10-21a.jpg

41 Chapter 10: Genetics: Mendel and Beyond Figure – Part 2 figure 10-21b.jpg

42 Chapter 10: Genetics: Mendel and Beyond Figure figure jpg

43 Chapter 10: Genetics: Mendel and Beyond Genes and Chromosomes The distance between genes on a chromosome is proportional to the frequency of crossing over.The distance between genes on a chromosome is proportional to the frequency of crossing over. Genetic maps are based on recombinant frequencies.Genetic maps are based on recombinant frequencies. Review Figures

44 Chapter 10: Genetics: Mendel and Beyond Figure figure jpg

45 Chapter 10: Genetics: Mendel and Beyond Sex Determination and Sex- Linked Inheritance Sex chromosomes carry genes that determine whether male or female gametes are produced.Sex chromosomes carry genes that determine whether male or female gametes are produced. Specific functions of X and Y chromosomes differ among species.Specific functions of X and Y chromosomes differ among species.44

46 Chapter 10: Genetics: Mendel and Beyond Sex Determination and Sex- Linked Inheritance In fruit flies and mammals, the X chromosome carries many genes, but the Y chromosome has only a few.In fruit flies and mammals, the X chromosome carries many genes, but the Y chromosome has only a few. Males have only one allele for most X-linked genes, so rare alleles appear phenotypically more often in males.Males have only one allele for most X-linked genes, so rare alleles appear phenotypically more often in males. Review Figures 10.25,

47 Chapter 10: Genetics: Mendel and Beyond Figure figure jpg

48 Chapter 10: Genetics: Mendel and Beyond Figure figure jpg

49 Chapter 10: Genetics: Mendel and Beyond Non-Nuclear Inheritance Cytoplasmic organelles such as plastids and mitochondria contain some heritable genes.Cytoplasmic organelles such as plastids and mitochondria contain some heritable genes.48

50 Chapter 10: Genetics: Mendel and Beyond Non-Nuclear Inheritance Cytoplasmic inheritance is generally by way of the eggCytoplasmic inheritance is generally by way of the egg Male gametes contribute only their nucleus to the zygote at fertilization.Male gametes contribute only their nucleus to the zygote at fertilization.49


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