Pedigree Project
As we have learned, DNA is the universal code to all life. Genetics is the study of how that DNA is passed
from generation to generation. During this project, we are going observe the inheritance patterns of
human traits exhibiting complete dominance. To do so, we will examine ourselves to determine which
trait we exhibit for each of the characteristics listed below. It will then be your responsibility to survey
the appearance of your parents (and siblings if applicable) to discover if they exhibit the same
phenotype as you. You will then use that information to investigate exactly how you acquired these
traits as well as the biological explanation behind their expression.
Feature
Mouth
Hair
Cheek
Chin
Ear
Hand
Phenotype
PTC paper tasting
Tongue Rolling
Widow’s peak
Dimples
Freckles
Y-shaped fissure
Lobe
Little finger
Mid-digit hair
Dominant
Taste
Roll
Having a widow’s peak
Dimples
Freckles
Cleft
Free
Curved
Hair
Recessive
No taste
Cannot roll
No peak
No dimples
No freckles
No cleft
Attached
Straight
No hair
Procedure
1. With a partner, examine your appearance to determine if you exhibit the dominant or recessive
version for each of the traits listed above.
2. Observe the phenotypes of your parents and that of every accessible member in your
immediate family. (You will be provided with PTC paper as well as regular paper strips to be
used as a control to take home with you.)
 Note: I realize that some of you may not have access to one or both your blood parents
for a variety of reasons. If this is the case, then please examine the phenotypes of your
guardian(s) (even if it is only 1 person). Even though this does not represent your actual
heredity, it can still be intriguing to examine the similarities and/or differences you
share with these individuals. You will answer the extension questions simply in a general
sense without including specific example of your personal heredity.
3. Construct a pedigree for each of the traits listed demonstrating the inheritance patterns in your
family.
4. You will now examine these pedigrees, and write a reflection demonstrating that you
understand the mechanisms that have occurred to produce the similarities/differences you see
between you and your family. After writing the reflection, answer the extension questions listed
below to demonstrate your ability to apply the knowledge you described in your reflection.
Reflection:
1. Begin by describing the biological process (meiosis) that occurs to allow traits to be passed from
parent to offspring in sexually reproducing organisms.
2. Then, explain in as much detail as possible the molecular process that leads to the expression of
your phenotype from the genotype you acquired from your parents. In other words, how do you
take the DNA that you receive as a diploid zygote (receiving 1 haploid set from each parental
gamete) and produce the phenotype that you see. Hint: discuss molecular biology (specifically
protein synthesis).
 Include a description of the difference between the expression of a dominant and
recessive trait in this discussion while citing specific examples from your phenotype.
Application Questions
1. For some of these traits, both of your parents may have exhibited a different phenotype than
you. Give an explanation for how these situations are possible citing the specific examples
where this occurred with your family. (If there is not an example of this in your pedigrees then
simply describe how this scenario could occur in general.)
2. Explain why for some of these traits we can be certain of your genotype but for others we
cannot. (If there is not an example of this in your pedigrees then simply describe how this
scenario could occur in general.)
3. As you study the phenotypes of your family, you will most likely notice that you share
similarities with each of your parents. If you have siblings, you will observe similar results with
them as well. Even so, it is unlikely that you display identical phenotypes for all of the
characteristics listed with any of them. Choose one of these individuals. Explain in detail how it
is possible for you to demonstrate similarities with them in certain aspects but to be different
from them in others. In this description, include the following terms: law of independent
assortment, law of segregation, crossing over, and random fertilization.
a. In other words, for this question you are discussing exactly how meiosis gives us genetic
variation.
4. Critique the following statement by giving a detailed explanation of your support or rebuttal. “A
dominant trait is more likely to be found in a population.” If you disagree, describe how a trait
actually becomes more common in a population.