Definition of letters used to represent alleles | Homework Help

You will need to pick a heritable trait in your (or your friend or relative’s if you have limited information about your biological family) family and build a pedigree consisted of three generations and at least 10 individuals.

Next to each square or circle on the pedigree, please write the name (feel free to use fictitious names to protect privacy) of the individual and possible genotype(s) this person may have for the trait being studied. Make sure you define which “letters” are used to represent which alleles. If someone is missing on your pedigree, represent them with a question mark and note if they had to have been affected or a carrier or if it is unknown.

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The DNA Learning Center has a great tutorial on how to make a pedigree! Use the link here (Links to an external site.) to visit their site before you start.

Which trait should you look at? To be able to easily follow and predict inheritance patterns, it is best to pick a trait that is not polygenic. But most human traits are.

If there is a known genetic disease in your family, this is a perfect chance for you to do some further investigation. Some human disorders controlled by a single gene are cystic fibrosis, phenylketonuria, sickle-cell disease, Tay Sachs disease, Achondroplasia, Huntington’s disease, Marfan syndrome, and hypercholesterolemia. Note that some of the disorders mentioned are dominant, and some are recessive.

Everyone in the family is healthy? Or family members suffer from diseases with multifactorial causes such as heart disease and diabetes? Then use this link to learn more about 10 observable human characteristics. Although the website suggests most of these characteristics (all except freckles, red/green colorblindness, and PTC tasting) may be polygenic or have environmental factors, you can treat them as monogenic and see if you see deviations from expected phenotypes within your family pedigree. This site also has pictures for your reference. You probably will not be able to do PTC tasting at home, but the other 9 are easily observable. You can also look at the “ear wax'” trait mentioned by Hank and his brother in the Crash Course video.

1. The pedigree (like the example above) with names and possible genotypes for most, if not all, individuals in the pedigree

2. Definition of “letters” used to represent alleles.

3. A brief written description of what trait you chose to analyze and how it is inherited (is it dominant or recessive, sex-linked, co-dominant or so on).


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