Pedigree Charts - Ueueufjur PDF

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PEDIGREE CHARTS Since genetic ratios do not hold for humans, the absence or presence of a particular trait is recorded from generation to generation. This is used to construct a genetic family tree called a pedigree chart. In constructing a pedigree chart, the following rules are followed: 1. Circles represent females and squares represent males. 2. The presence of a character or trait is represented by a solid square or circle. A blank shape represents the absence of the trait in the phenotype. Half filled squares or circles represent carriers; persons carrying a trait not obvious in the phenotype. 3. Roman numerals represent generations. Arabic numerals represent individuals. 4. Horizontal lines between individuals represent mating. Offspring are shown by vertical lines off mating lines. Offspring are linked by the same horizontal line.

An illustration of some of these conventions follows in the pedigree chart below.

A Pedigree Chart: Freckles in Humans...