Heredity and Environment Calculating Phenotypes and Genotypes One way to calculate the odds that parents with a particular gene in their geno- type will pass it on to their children is to draw a table with the father’s two genes for that genotype on the top and the mother’s two genes on the left. Father’s two genes F 1 F 2 Mother’s M 1 two genes M 2 The box is filled in very simply. The letters at the top of each column are writ- ten into the boxes reading down and the letters at the side are written into the boxes reading across. Father’s two genes F 1 F 2 Mother’s M 1 two genes M 2 As you can see from examining the boxes, a child could inherit any one of four possible combinations from the parents’ two pairs of genes. The chances of each child inheriting one of these combinations is one in four, or 25 percent. F 1 M 1 F 2 M 1 F 1 M 2 F 2 M 2
HANDOUT 4 (continued) Consider how this works in practice. When both parents have two brown- eye genes, all the children will have brown eyes as well as two brown-eye genes.
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- Fall '16