Biology 1001A Lecture Notes - Lecture 13: Melanocortin 1 Receptor, 3Cr Melbourne, Punnett Square
25 Feb 2016
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One allele is recessive is dominant and another is recessive is not enough for us to predict their genotype in terms of mendelian genetics. We can use punnet squares to make predictions about genotypes, phenotypes and allele frequency in the next generation. Cross two heterozygous pigs (w dominant: 3:1 ratio of brown pigs to red pigs phenotypes and 1:2:1 ratio of genotypes. We don"t see this in real life because the allele frequencies are not always 50/50 (right pic) In the wild the allele frequency of w relative to r can be anything. Scale up the punnet square: implicitly using probability theory, to be rr (1/2 prob of getting it from mom x prob of getting it from dad = 1/4 , monohybrid cross. Gametes encounter each other in proportion to their frequency. The proportion that ends up with rr is 16% and ww is 36% in the population.
