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L25 (Slide 1 - 21) & L26 (Slide 26 - 49) Linkage, Recombination &…

- - - - Parent 1
        R/y . R/y
        
        Gamete 1
        r.Y
      - Parent 2
        r/Y . r/Y
        
        Gamete 2
        R.y
        
        F1 - (1st Gen)
        R/y . r/Y
        
        Self Fertlisation: F1 x F1
        
        1/4 of F2 = Wrinkled (r/r)
        
        3/4 of these = Yellow (Y/-)
        
        1 more item...
        
        1/4 of these = Green (y/y)
        
        1 more item...
        
        3/4 of F2 = Round (R/-)
        
        3/4 of these = Yellow (Y/-)
        
        1 more item...
        
        1/4 of these = Green (y/y)
        
        1 more item...
    - - 1. Genes are on different chromosomes=
        
        A/a ; B/b
      - 2. Genes are on the same chromosome=
        
        AB/ab
      - 3 If the location of the two genes is not known=
        
        A/a • B/b*
  - - - Y/y
        
        Y/y x Y/y
        
        1/2 = Y/y
        
        1/4 = Y/Y
        
        1/4 = y/y
        
        Y/y x y/y
        
        1/2 = y/y
        
        1/2 = Y/y
- - - - Linked Genes Remain together during meiosis
        Linked genes travel together in meiosis, arriving at the same destination ( ie same gamete) and are not expected to assort independently
        
        Although we find many examples which contradict Mendels law of assortment, all characteristics examined by Mendel in peas did assort independently!!
        
        Sweet peas - William Bateson:
        (Homozygous purple flowers, long pollen) X
        (homozygous red flowers, round pollen)
        
        All F1 = Heterozygous Purple flowers, long pollen (purple dominant over red, long over round)
        
        Self fertilised F1,
        
        F2 did not conform with 9:3:3:1 ratio expected from Independently assorting alleles.
        
        An excess of F2 had parental phenotypes hinting that the alleles did not assort independently
        .... two loci lie close together on same chr.
        
        Let’s Review:
        
        Consider;
        
        1st Parent (AABB) produces gametes AB,
        
        2nd parent (aabb), produces gametes ab
        
        F1 genotype = ABab
        
        1 more item...
        
        PL/PL x pl/p/l