Genetics Part 2
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Genetics Part 2

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    Genetics Part 2 Genetics Part 2 Presentation Transcript

    • Advanced Genetics McCammon Biology I
    • Mendelian Genetics
      • These are the types of problems we had before Christmas.
      • Monohybrid crosses
      • Dihybrid crosses
      • Test cross
    • Incomplete Dominance
      • This is a condition in which NEITHER allele for a particular trait is dominant over the other.
      • For example: red-flowered snapdragons crossed with white ones yield pink.
    • Incomplete Dominance
      • For these problems, you should make a key for each problem in addition to the Punnett Square, genotype, and phenotype.
      • RR = Red (One of the two traits)
      • R’R’ or WW = White (The other trait)
      • RR’ or RW = Pink (Blending of the two traits)
    • ABO Blood Types: A Case of Codominance
      • In codominance, both alleles are expressed in heterozygotes.
      • In codominance, instead of NEITHER allele being dominant, BOTH alleles are dominant.
    • ABO Blood Types: A Case of Codominance
      • For these problems, you should also make a key for each problem in addition to the Punnett Square, genotype, and phenotype.
      • F B F B = Black Feathers (One Trait)
      • F W F W = White Feathers (The other Trait)
      • F B F W = Black and White Speckled Feathers (Heterozygous = spotted)
    • ABO Blood Types: A Case of Codominance
      • Blood type is determined by markers produced by three genes – This is called multiple alleles.
        • I A and I B are each dominant to i, but are codominant to each other.
        • Therefore, some persons can express I A and I B and have AB Blood Type.
      • The four blood types are
      • A = I A I A or I A i
      • B = I B I B or I B i
      • AB = I A I B only
      • 0 = ii only
      ABO Blood Types: A Case of Codominance
    • Autosomes and Sex Chromosomes
      • There are 44 autosomes (22 pairs) and 2 sex chromosomes (1 pair)
    • Autosomes and Sex Chromosomes
      • Gender is determined by sex chromosomes
        • Human females have two X chromosomes
        • Human males have one X chromosome and one Y chromosome.
        • All normal human eggs carry only one X chromosome
        • Half of the sperm carry an X chromosome and the other half carry a Y chromosome.
    • Autosomes and Sex Chromosomes
      • Sex determination in humans
        • If an X bearing sperm fertilizes an X bearing egg, a female results.
        • If a Y bearing sperm fertilizes an X bearing egg, a male results.
          • XX – female
          • XY - male
    • Sex-Linked Traits
      • Some genes are only found on sex chromosomes.
        • Genes for color blindness; gene for male pattern baldness; gene for hemophilia.
    • Sex-Linked Traits
      • Here are the genotypes and you will need to know:
      • X B X B = Normal female
      • X B Y = Normal Male
      • X B X b = Normal female (but she’s a carrier)
      • X b X b = Affected female
      • X b Y = Affected male
      • Y will not have a letter.
    • Pedigrees
      • A pedigree is a diagram that shows the history of trait.
      • Where Punnett’s squares predict the future, pedigrees map the past.
    • Pedigrees
      • It is used by geneticists to determine if a trait is sex-liked.
        • Squares represent males
        • Circles represent females
        • A horizontal line represents a mating
        • A vertical line represents children
        • If the circle or square is shaded in, this means they are affected
    • Pedigrees
        • A triangle means abortion or miscarriage
        • A diamond indicates a person of unknown sex
        • A diagonal line through a circle or square means the person is dead.
        • A diagonal line through a mating means divorce or the pair is not together anymore.
        • The children are listed in birth order.
        • Each generation is marked with roman numerals
        • Each individual is marked with a number starting at the top left.