Family Pedigree Instructions
Build a diagram of your family, using proper pedigree symbols. Indicate where you are on the pedigree.
Select one trait from the list below to find one where there are different phenotypes in at least two people in the family.**
Color or shade the pedigree to show the phenotypes for all people. Place a ? for each person on the tree that you were not able to test.
Research (using a reliable source, does not need to be primary or secondary) whether this trait is dominant, recessive, incomplete, or codominant) and cite your sources.
List the genotype(s) clearly for all individuals in the pedigree. Assume that the trait is not sex-linked unless you know otherwise.
Predict the probability of one couple on your pedigree having a child of a particular genotype. Make a Punnett Square to show the probability.
Heritable (to some extent)*** Human Traits
Asparagus-urine: odor vs no odor
Blood type: A/B/AB/O
Blood type: Rh+ vs Rh-
Cleft chin: present vs absent
Dimples vs No Dimples
Ear lobes: attached vs unattached
Earwax: Dry vs. Wet
Eyebrows: joined vs separated
Freckles vs no freckles
Handedness: right vs left
Hair between finger joints: hair vs. no hair
Hair shape: straight vs curly
Hair whorl: clockwise vs counter-clockwise
Straight thumb vs Curved (hitchikers) thumb
Little finger: bent vs. straight
Polydactyly
Red/Green color blindness
Tongue-roller: curler vs non-curler
White forelock: present vs absent
Any known distinctive family trait or tendency (e.g. twins, webbed toes, etc.) or disease tendency (e.g. diabetes, heart disease, hypoglycemia, etc.) If “twins”, distinguish “monozygotic” from “dizygotic”
FAQs:
Q1) What if I’m adopted or don’t know my family?
A1) If your family is not entirely biologically related to you (adopted, etc.), or if it is very small, you may select another suitable family (neighbor, or friend’s family). You may use the family of another student in the class ONLY if you trace a different trait in that family.
Q2) My family is really small, just me and my parents – what do I do?
A2) The family should be as large as possible, but you could get by with 2 parents with one child. You will not lose credit as long as you have 2 parents and a child on it somewhere. If you don’t have that – see Q1.
Q3) My siblings and I have different fathers (or mothers), what do I do?
A3) You can draw the shared parent in the middle and then have two “marriage lines” from them – one to the right and one to the left, put the relevants kids down from them connected the corrent parent set.
Q4) None of these traits work for my family, what should I do?
A4) If you’ve looked at all of them and everyone has exactly the same phenotypes for all 20 of them, let me know and I’ll find you some other options or select another family (friend or neighbor) until difference are found.
Q5) I did this and something looks really weird – the genotypes don’t work out. Is my dad not really my dad?!?!?!
A5) Your dad is your dad – the problem is with the genetics. None of these traits are 100% absolute and weird things happening on your pedigree should not make you panic. Some traits have variable penetrance (not everyone expresses the alleles that they have), some traits are polygenic (coded for by many genes), some have variable expressivity (some genes are expressed more strongly in others), and sometimes the environment can affect the traits too. Just note these variances in your pedigree. These traits listed above are partially genetic, but even in this example, there are weird things that happen ALL THE TIME.
Q6) What are some good tools to make a pedigree?
A6) You can draw this neatly by hand, or do it on the computer. You can build the shapes in powerpoint/Google slides or use a whiteboard. One site to help you get started it: https://pedigree.progenygenetics.com/ (Links to an external site.) but you won’t be able to do the whole thing there. Build the pedigree there then screenshot it and fill in the shapes and genotypes yourself in another document.