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Genetics

Genetics. Which one of these is not like the other???. Mutants. Mutants. Contrasting Traits. Relationship of Phenotype to Genotype. The phenotype is the outward expression of all alleles governing a given trait The genotype is the alleles present in the genome

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Genetics

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  1. Genetics

  2. Which one of these is not like the other???

  3. Mutants

  4. Mutants

  5. Contrasting Traits

  6. Relationship of Phenotype to Genotype The phenotype is the outward expression of all alleles governing a given trait The genotype is the alleles present in the genome The gene products encoded by the gene (alleles) give rise to the phenotype

  7. A Controlled Cross between Two Plants

  8. Mendel’s Experiment 1 (Part 1)

  9. Mendel’s Experiment 1 (Part 2)

  10. Mendel’s Explanation of Experiment 1

  11. Phenotype Dominant trait One that appears exclusively in F1 generation Recessive trait One masked in the F1 but reappearing in some of F2 offspring

  12. Mendel’s Monohybrid Cross Results

  13. Mendel’s Law of Segretation Each parent contains two factors governing a particular trait 2 dominants 1 dominant + 1 recessive 2 recessives The factors are separated during reproduction and only 1 from each parent is passed to offspring Alleles of a gene segregate during meiosis Each somatic cell contains 2 alleles of each gene, while gametes contain only 1.

  14. Meiosis Accounts for the Segregation of Alleles

  15. Meiosis Accounts for the Segregation of Alleles

  16. Homozygosity vs Heterozygosity Homozygosity – alleles are same Heterozygosity alleles are different Homozygous dominant and heterozygous individuals have same phenotype (dominant) Homozygous recessive individuals have recessive phenotype

  17. Homozygous or Heterozygous?

  18. Dihybrid Crosses and Independent Assortment What is result of crosses between individuals differing in two traits? Do alleles of for different traits segregate together or separately?

  19. Meiosis Accounts for Independent Assortment of Alleles

  20. Relationships between Alleles In diploid organisms there are 2 alleles for every gene (locus) in the genome One allele was inherited from father and the other from mother Multiple alleles may exist in a population of organisms although only 2 are present at any one time in an individual Each gene encodes a gene product (protein or RNA) Alleles interact in following ways Complete dominance/recessiveness Co-dominance Incomplete dominance

  21. Phenotype vs Genotype Phenotype – appearance/function Genotype – set of alleles present in genome

  22. ABO Blood Types: Multiple Alleles Showing Complete Dominance or Co-dominance A dominant to O B dominant to O A co-dominant to B Co-dominance results when alleles each encode a functional enzyme, however, the encoded enzymes differ in their specificities Phenotype

  23. Incomplete Dominance r encodes a non-functional protein R encodes a functional protein Rr makes ½ the amount of R-protein as an RR flower Rr flowers are less intensely colored

  24. Pedigree Analysis

  25. Pedigree Analysis

  26. Crossing Over Results in Genetic Recombination

  27. Linkage: When Alleles Do Not Sort Independently

  28. Recombinant Frequencies

  29. Steps toward a Genetic Map

  30. Map These Genes (Part 1)

  31. Map These Genes (Part 2)

  32. Figure 10.22 Map These Genes (Part 3)

  33. Figure 10.22 Map These Genes (Part 4)

  34. Figure 10.22 Map These Genes (Part 5)

  35. Eye Color Is a Sex-Linked Trait in Drosophila

  36. Figure 10.24 Red-Green Color Blindness is a Sex-Linked Trait in Humans

  37. Epistasis Epistasis occurs when the alleles of one gene cover up or alter the expression of alleles of another gene. Coat color in mice: B allele produces a banded pigment pattern, called agouti, while the b allele results in unbanded hairs. genotypes BB or Bb produce agouti. genotype bb is black. Alleles at the A locus determine if any pigmentis made. The genotypes AA and Aa have color andaa are albino.

  38. Epistatic Gene Interaction a A Sequential pigment deposition B b Constant pigment deposition B is an enzyme that actively interupts deposition Non-functional pigment producing enzyme Functional pigment producing enzyme A is an enzyme that actively synthesizes pigment

  39. Epistasis genotype genotype pigment precursor molecule AA or Aa BB or Bb pigment molecule Striped hair pigment precursor molecule aa BB or Bb pigment molecule pigmented hair pigment precursor molecule AA or Aa bb Solid color hair pigment molecule pigment precursor molecule aa bb pigment molecule pigmented hair Pigment producing enzyme Deposition of pigment in hair pigment precursor molecule pigment molecule pigmented hair

  40. Quantitative Traits Traits exhibiting a range of phenotypic variance that can be quantified (measured) Height, weight, seed yield, life span etc… Traits are simultaneously controlled by many alleles Additive alleles Proteins encoded by various alleles function in tandem to influence trait Genes functioning in this manner are referred to as quantitative trait loci (QTLs)

  41. Quantitative Trait Loci 2 genes control seed color for a given plant and each gene has 2 alleles Genes: A/a, B/b, Any given plant can be of one of the following genotypes AABB, AaBB, aaBB, AABb, AAbb, AaBb, Aabb, aaBb, aabb Each allele of each gene can “add” a given amount of activity to generating a color phenotype. A and B add the most color, a and b add less color Therefore a range of colors can exist (5 categories) AABB – darkest AABb, AaBB – next darkest AaBb, aaBB, AAbb – mid range color Aabb, aaBb – very little color aabb – least color

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