Autosomal linkage

Chromosome pair 23 is the XY or sex chromosome
Chromosome pairs 1 through 22 are called "autosomal"
If number of traits exceeds number of chromosome pairs
Then more than one gene per chromosome (linkage)

  • linked alleles could be permanently linked
    . . - and would exhibit pleiotropy
  • linked alleles could be exchanged between chromosomes
    . . - and would exhibit cross-over frequencies
  • cross-over frequency estimates
    . . - separation distance between genes on chromosome
    . . - map units for chromosome mapping

    dihybrid
    normal    		 dihybrid
    linked    		 monohybrid
    pleiotropic
    offspring offspring
    5% crossover    		 offspring
    genotype count phenotype prob prob prob
    AABB 1 type A
    type B    		 6.25% 22.56% 25%
    AABb 2 type A
    hybrid B    		 12.5% 2.38% 0
    AaBB 2 hybrid A
    type B    		 12.5% 2.38% 0
    AaBb 4 hybrid A
    hybrid B    		 25.0% 45.25% 50%
    AAbb 1 type A
    type b    		 6.25% 0.06% 0
    Aabb 2 hybrid A
    type b    		 12.5% 2.38% 0
    aaBB 1 type a
    type B    		 6.25% 0.06% 0
    aaBb 2 type a
    hybrid B    		 12.5% 2.38% 0
    aabb 1 type a
    type b    		 6.25% 22.56% 25%

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    © 2004 Prof. LaFrance, Ancilla College