State the dominant traits

Genetics & Variability

This week we are making our own family trees. Family trees are used to understand how people in families are biologically (and culturally) related. They are also used to show how traits are inherited from past generations and predict the probability of inheriting traits in future generations.

Use the directions below to construct your own family tree that follows a trait through three continuous generations (for example: you, your parents, and your grandparents)

1. Start here to learn how to read and make a family tree.  Start here to learn how to blend together how to make a family tree with following the inheritance pattern of a trait. I would also check out week 5’s lecture notes and (if you decided to purchase it) page 45-50 in the France lab book.

2. Decide if you want to outline your family tree or a made up one. Choose a trait in that family (one that does not violate HIPAA or patient privacy laws) or make one up. Trace that trait through at least three generations and choose something visible or whatever interests you so it’s easy to follow. Many traits, like hair or eye color, have several genes that code for it, so those kinds of traits might not be easy to trace.

3. Then ask yourself: How is the trait inherited – is it a dominant, recessive, or sex-linked trait? Make sure to indicate the inheritance pattern in your tree as well as a legend so we know how to read it. Be sure to read directions on how to construct a tree, which, again are listed here, in the module, and in the France lab book (pages 45-50). Please do not guess – for example, I will notice if you assume that they trait is “dominant” because it appears frequently in the tree. I will redirect you to those directions to redo the assignment if you are guessing.

4. Draw your tree out on paper by hand or on the computer, as you wish. Once you have made your tree, please start a thread to share your tree with the class along with commentary on your learning experience. Commentary should include: what is the trait, is it a dominant or recessive trait, and what are the genotypes of the individuals in the tree.

If you do not want to share your tree or believe it may violate HIPAA, you are welcome to send it to me via email and I can go through it with you individually. Generally, to avoid the HIPAA issue, it is best to use different names and a made-up trait.

You don’t have to be an artist – you can draw the pedigree by hand, scan it, and upload. You do not have to share the name of the trait or the names of family members either.

5.  Things to be aware of:

• Do you have contact with your biological relatives (don’t answer that here, please)? If you don’t, you are welcome to make up a tree, use one of the trees in the lab book, or use a friend’s family tree and trace a trait.
• Please do not use hair or eye color as your trait. Lighter pigments behave in a recessive manner and darker ones behave in a dominant manner.  Also, pigmentation is polygenic and highly influenced by sunshine and personal augmentation (coloring hair, contacts, tanning) so sometimes it’s hard to tell what the pigments really are.

6. You will be tested on how to read a pedigree, how to follow a trait, and name how it is inherited.

7. When you figure out if the trait is inherited as a dominant or recessive, it’s not possible to guess. Dominant does not mean more frequent or more common (more here). Please try to figure it out using the information from the week 5 module.