Summarize the following:
If you are looking at a pedigree that traces a specific trait, there should be some information included about what trait it is tracing. To trace the trait, start at the oldest generation. This will allow you to see how it has been passed down through the generations. Look for a roman numeral on the side of the pedigree that shows which generation is number 1. If there are no roman numerals included on the pedigree you can still easily determine the first generation. Look for the subjects that only have a line indicating a reproductive relationship connected to them. This indicates that the subjects below them are their children and their parents are not represented on the pedigree. The pedigree should also give you information about all of the symbols on the pedigree that are not standard. By looking at the symbols on the pedigree you can see who has been affected by the trait and who has not. Look for filled in circles and squares to see who has been affected. In some cases, just by looking at who has been affected by a trait you can trace it through every generation. If every generation has an occurrence of a trait then that trait is called dominant. A dominant trait is one that is will always be expressed if it is present in someone's DNA. As a genetic trait is passed down, there can be people or animals who carry the trait in their DNA but are not affected by the trait. To determine if someone is likely a carrier of a trait, you need to look at the generation before them and the generation after them. If the generation before this person was affected by the trait and a person after them is affected and has no other relatives that have a history of this trait in their family, then that person is a carrier. Determining who a carrier is can be difficult when a person has several ancestral lines that could be the source of a trait. By tracing the relationships in a pedigree and seeing who had a trait and who did not, you can get insight into whether the trait is carried on the sex chromosomes, called the x and the y. Look closely at parent and child relationships and see which parents and children had a trait and which did not. For example, if males of every generation have the same genetic trait, then that trait is likely carried on the y chromosome, which females do not have. If a trait impacts both males and females, it is not linked to sex and is carried on a different type of chromosome. This type of trait is called an autosomal trait.
Read the key on the pedigree and identify the oldest generation. Determine whether the trait has shown up in every generation. Analyze the pedigree for recessive carriers. Determine whether the trait is sex linked.