GENETICS
Genetics• The study of heredity.               heredity• Gregor Mendel (1860’s) discovered the  fundamental principles of ...
Genetics• Alleles  1. Alternative forms of genes.  2. Units that determine heritable traits.  3. Dominant alleles (TT - ta...
Phenotype• Outward appearance• Physical characteristics• Examples:         1.     tall pea plant         2.     dwarf pea ...
Genotype• Arrangement of genes that produces the  phenotype• Example:  1. tall pea plant           TT = tall (homozygous d...
Punnett square• A Punnett square is used to show the  possible combinations of gametes.                           gametes
Breed the P generation• tall (TT) vs. dwarf (tt) pea plants             T     T         t         t
tall (TT) vs. dwarf (tt) pea plants       T     T             Tt      produces thet      Tt                     F1 generat...
Breed the F1 generation• tall (Tt) vs. tall (Tt) pea plants               T     t          T          t
tall (Tt) vs. tall (Tt) pea plants     T     t                      produces the     TT    Tt         F2 generation T     ...
Monohybrid Cross• A breeding experiment that tracks the inheritance  of a single trait.• Mendel’s “principle of segregatio...
Homologous Chromosomeseye color locus                       eye color locusB = brown eyes                        b = blue ...
Meiosis - eye color                                     B                    B                     sperm                  ...
Monohybrid Cross• Example:  Example         Cross between two heterozygotes                  for brown eyes (Bb)BB = brown...
Monohybrid Cross              B    b                        1/4 = BB - brown eyed          B   BB   Bb   1/2 = Bb - brown ...
Dihybrid Cross• A breeding experiment that tracks the inheritance  of two traits.• Mendel’s “principle of independent asso...
Independent Assortment• Question: How many gametes will be produced            for the following allele arrangements?• Rem...
Answer:1. RrYy: 2n = 22 = 4 gametes      RY Ry rY ry2. AaBbCCDd: 2n = 23 = 8 gametes     ABCD ABCd AbCD AbCd     aBCD aBCd...
Dihybrid Cross• Example:        cross between round and yellow                  heterozygous pea seeds. R   = round       ...
Dihybrid Cross     RY   Ry   rY   ryRYRyrYry
Dihybrid Cross      RY    Ry      rY    ry                                 Round/Yellow:     9RY RRYY RRYy       RrYY   Rr...
Test Cross• A mating between an individual of unknown genotype  and a homozygous recessive individual.• Example: bbC__ x b...
Test Cross     • Possible results:       bC    b___               C                bC     b___                            ...
Incomplete Dominance• F1 hybrids have an appearance somewhat in  between the phenotypes of the two parental  varieties.• E...
Incomplete Dominance      R   R               produces ther    Rr   Rr               F1 generationr    Rr   Rr   All Rr = ...
Codominance• Two alleles are expressed (multiple alleles)                                      alleles  in heterozygous in...
Codominance• Example:          homozygous male B (IBIB)                              x                    heterozygous fem...
Codominance• Example: male O (ii) x female AB (IAIB)               IA     IB         i    I Ai   IBi   1/2 = IAi          ...
Codominance• Question:  Question       If a boy has a blood type O and                 his sister has blood type AB,      ...
Codominance• Answer:      IA     iI B I AI B          Parents:                    genotypes = IAi and IBi                 ...
Sex-linked Traits• Traits (genes) located on the sex  chromosomes• Example:      fruit flies     (red-eyed male) X (white-...
Sex-linked Traits                 Sex Chromosomes                         fruit fly                         eye colorXX ch...
Sex-linked Traits• Example:       fruit flies     (red-eyed male) X (white-eyed female)• Remember: the Y chromosome in mal...
Sex-linked Traits      XR      yXr   XR Xr   Xr y                    1/2 red eyed and female                    1/2 white ...
Population Genetics• The study of genetic changes in populations.                                  populations• The scienc...
Question:• How do we get this equation?Answer:   “Square” 1 = p + q                          ↓                    12 = (p ...
Hardy-Wienberg equation• Five conditions are required for Hardy-Wienberg  equilibrium.  1. large population  2. isolated p...
Important• Need to remember the following:    p2 = homozygous dominant    2pq = heterozygous    q2 = homozygous recessive
Question:• Iguanas with webbed feet (recessive trait) make  up 4% of the population. What in the population  is heterozygo...
Answer:1. q2 = 4% or .04   q2 = .04      q = .22. then use 1 = p + q            1 = p + .2   1 - .2 = p    .8 = p3. for he...
Hardy-Wienberg equation          1 = p2 + 2pq + q2•   64% = p2    = homozygous dominant•   32% = 2pq   = heterozygous•   0...
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Genetics

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Genetics

  1. 1. GENETICS
  2. 2. Genetics• The study of heredity. heredity• Gregor Mendel (1860’s) discovered the fundamental principles of genetics by breeding garden peas. peas
  3. 3. Genetics• Alleles 1. Alternative forms of genes. 2. Units that determine heritable traits. 3. Dominant alleles (TT - tall pea plants) plants a. homozygous dominant 4. Recessive alleles (tt - dwarf pea plants) plants a. homozygous recessive 5. Heterozygous (Tt - tall pea plants) plants
  4. 4. Phenotype• Outward appearance• Physical characteristics• Examples: 1. tall pea plant 2. dwarf pea plant
  5. 5. Genotype• Arrangement of genes that produces the phenotype• Example: 1. tall pea plant TT = tall (homozygous dominant) 2. dwarf pea plant tt = dwarf (homozygous recessive) 3. tall pea plant Tt = tall (heterozygous)
  6. 6. Punnett square• A Punnett square is used to show the possible combinations of gametes. gametes
  7. 7. Breed the P generation• tall (TT) vs. dwarf (tt) pea plants T T t t
  8. 8. tall (TT) vs. dwarf (tt) pea plants T T Tt produces thet Tt F1 generationt Tt Tt All Tt = tall (heterozygous tall)
  9. 9. Breed the F1 generation• tall (Tt) vs. tall (Tt) pea plants T t T t
  10. 10. tall (Tt) vs. tall (Tt) pea plants T t produces the TT Tt F2 generation T 1/4 (25%) = TT Tt tt 1/2 (50%) = Tt t 1/4 (25%) = tt 1:2:1 genotype 3:1 phenotype
  11. 11. Monohybrid Cross• A breeding experiment that tracks the inheritance of a single trait.• Mendel’s “principle of segregation” a. pairs of genes separate during gamete formation (meiosis). b. the fusion of gametes at fertilization pairs genes once again.
  12. 12. Homologous Chromosomeseye color locus eye color locusB = brown eyes b = blue eyes This person would have brown eyes (Bb) Paternal Maternal
  13. 13. Meiosis - eye color B B sperm B Bb haploid (n) bdiploid (2n) b b meiosis I meiosis II
  14. 14. Monohybrid Cross• Example: Example Cross between two heterozygotes for brown eyes (Bb)BB = brown eyes B b maleBb = brown eyes gametesbb = blue eyes B Bb x Bb b female gametes
  15. 15. Monohybrid Cross B b 1/4 = BB - brown eyed B BB Bb 1/2 = Bb - brown eyedBb x Bb 1/4 = bb - blue eyed b Bb bb 1:2:1 genotype 3:1 phenotype
  16. 16. Dihybrid Cross• A breeding experiment that tracks the inheritance of two traits.• Mendel’s “principle of independent assortment” a. each pair of alleles segregates independently during gamete formation (metaphase I) b. formula: 2n (n = # of heterozygotes)
  17. 17. Independent Assortment• Question: How many gametes will be produced for the following allele arrangements?• Remember: 2n (n = # of heterozygotes) 1. RrYy 2. AaBbCCDd 3. MmNnOoPPQQRrssTtQq
  18. 18. Answer:1. RrYy: 2n = 22 = 4 gametes RY Ry rY ry2. AaBbCCDd: 2n = 23 = 8 gametes ABCD ABCd AbCD AbCd aBCD aBCd abCD abCD3. MmNnOoPPQQRrssTtQq: 2n = 26 = 64 gametes
  19. 19. Dihybrid Cross• Example: cross between round and yellow heterozygous pea seeds. R = round RrYy x RrYy r = wrinkled Y = yellow RY Ry rY ry x RY Ry rY ry y = green possible gametes produced
  20. 20. Dihybrid Cross RY Ry rY ryRYRyrYry
  21. 21. Dihybrid Cross RY Ry rY ry Round/Yellow: 9RY RRYY RRYy RrYY RrYy Round/green: 3Ry RRYy RRyy RrYy Rryy wrinkled/Yellow: 3rY RrYY RrYy rrYY rrYy wrinkled/green: 1ry RrYy Rryy rrYy rryy 9:3:3:1 phenotypic ratio
  22. 22. Test Cross• A mating between an individual of unknown genotype and a homozygous recessive individual.• Example: bbC__ x bbcc BB = brown eyes Bb = brown eyes bC b___ bb = blue eyes bc CC = curly hair Cc = curly hair cc = straight hair
  23. 23. Test Cross • Possible results: bC b___ C bC b___ cbc bbCc bbCc or bc bbCc bbcc
  24. 24. Incomplete Dominance• F1 hybrids have an appearance somewhat in between the phenotypes of the two parental varieties.• Example: snapdragons (flower)• red (RR) x white (rr) R R RR = red flower r rr = white flower r
  25. 25. Incomplete Dominance R R produces ther Rr Rr F1 generationr Rr Rr All Rr = pink (heterozygous pink)
  26. 26. Codominance• Two alleles are expressed (multiple alleles) alleles in heterozygous individuals. individuals• Example: blood 1. type A = IAIA or IAi 2. type B = IBIB or IBi 3. type AB = IAIB 4. type O = ii
  27. 27. Codominance• Example: homozygous male B (IBIB) x heterozygous female A (IAi) IB IB IA I AI B I AI B 1/2 = IAIB 1/2 = IBi i I Bi IBi
  28. 28. Codominance• Example: male O (ii) x female AB (IAIB) IA IB i I Ai IBi 1/2 = IAi 1/2 = IBi i I Ai IBi
  29. 29. Codominance• Question: Question If a boy has a blood type O and his sister has blood type AB, what are the genotypes and phenotypes of their parents.• boy - type O (ii) X girl - type AB (IAIB)
  30. 30. Codominance• Answer: IA iI B I AI B Parents: genotypes = IAi and IBi phenotypes = A and Bi ii
  31. 31. Sex-linked Traits• Traits (genes) located on the sex chromosomes• Example: fruit flies (red-eyed male) X (white-eyed female) red white
  32. 32. Sex-linked Traits Sex Chromosomes fruit fly eye colorXX chromosome - female Xy chromosome - male
  33. 33. Sex-linked Traits• Example: fruit flies (red-eyed male) X (white-eyed female)• Remember: the Y chromosome in males does not carry traits.RR = red eyed XR yRr = red eyedrr = white eyed XrXy = male XrXX = female
  34. 34. Sex-linked Traits XR yXr XR Xr Xr y 1/2 red eyed and female 1/2 white eyed and maleXr XR Xr Xr y
  35. 35. Population Genetics• The study of genetic changes in populations. populations• The science of microevolutionary changes in populations. populations• Hardy-Weinberg equilibrium: the principle that shuffling of genes that occurs during sexual reproduction, by itself, cannot change the overall genetic makeup of a population.• Hardy-Wienberg equation: 1 = p2 + 2pq + q2
  36. 36. Question:• How do we get this equation?Answer: “Square” 1 = p + q ↓ 12 = (p + q)2 ↓ 1 = p2 + 2pq + q2
  37. 37. Hardy-Wienberg equation• Five conditions are required for Hardy-Wienberg equilibrium. 1. large population 2. isolated population 3. no net mutations 4. random mating 5. no natural selection
  38. 38. Important• Need to remember the following: p2 = homozygous dominant 2pq = heterozygous q2 = homozygous recessive
  39. 39. Question:• Iguanas with webbed feet (recessive trait) make up 4% of the population. What in the population is heterozygous and homozygous dominant. dominant
  40. 40. Answer:1. q2 = 4% or .04 q2 = .04 q = .22. then use 1 = p + q 1 = p + .2 1 - .2 = p .8 = p3. for heterozygous use 2pq 2(.8)(.2) = .32 or 32%4. For homozygous dominant use p2 .82 = .64 or 64%
  41. 41. Hardy-Wienberg equation 1 = p2 + 2pq + q2• 64% = p2 = homozygous dominant• 32% = 2pq = heterozygous• 04% = q2 = homozygous recessive• 100%

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