A pedigree chart is a mapping of a family tree that focuses specifically on whether or not members of the family have a genetic variation. The chart enables you to determine whether a trait is dominant or recessive, as well as if it is X-linked or autosomal. Using this information, it is possible to better determine whether a child born to a couple is likely to also have the same trait.
- Skill level:
- Moderately Easy
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Things you need
- Detailed family history (the more detailed, the better)
Keep each familial generation on its own row when you begin drawing the tree. For example, an individual's parents, aunts and uncles would be on the row above him; siblings and cousins would be on the same row as he; and children, nieces and nephews would be on the row beneath him.
Use the appropriate gender shape for each member of the pedigree chart. Women are represented with a circle, and males are represented with a square.
Use lines to show relations. A horizontal line between a circle and square shows a married couple that produced offspring. Children are represented by drawing a vertical line down from the line joining the couple, a horizontal line extending over all the children from that couple and a vertical line coming down from this line to each child.
Use lines to denote twins, with a small alteration to the way other children are noted. Fraternal twins should be connected to the parents' offspring line with a pair of diagonal lines, so they each touch the horizontal line at the same point. In addition, a horizontal line between the two children is used to denote identical twins.
Colour in the shapes of those who have the trait you are charting.
Check to see if the trait is dominant or recessive. A dominant trait must be had by one of the parents to be passed on, whereas a recessive trait can be passed on even when neither parent displays the trait. If any children have the trait while neither parent does, the trait is recessive.
Determine if the trait is X-linked or autosomal. If only males have the trait, it is X-linked. If any females are affected by the trait it is autosomal.
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