Download C) Genetics Family Part 1

Name:___________________________________
Period:______
Genetics Lab: What Are Some Traits in Your Family?
Adapted from Donald Galen
1994 Woodrow Wilson Collection
INTRODUCTION
Heredity is the passing on of traits from parents to offspring. Everyone is usually interested in where
their traits come from. Was it your mother who gave you your brown eyes or your father? Or could it
have been a combination of both of them? A diagram showing the transmission of a trait through
several generations of a family is called a pedigree. You will prepare four pedigree designs of your
family's genetics. After you are finished collecting the data, you will construct the pedigree
representing two, three, or four generations of four of the traits. (1st generation = you and siblings;
2nd generation = parents, aunts and uncles; 3rd generation = grandparents; etc.). You will be
exploring genotypes for 10 different traits in your family. The traits are: ear lobe attachments, tongue
rolling, hitchhiker's thumb, mid-digital hair, widow’s peak, thumb crossing, toe length, cleft chin,
freckles, and ear-wiggling. You will begin at the bottom of the pedigree design with you and your
genetic brothers and/or sisters. A square will be used to represent a male person and a circle for a
female person. The genotype must be expressed under the person that you are representing. The
shading of either a square or a circle indicates the possession of the recessive allele trait. Each
marriage or mating generation is indicated by a Roman numeral. The square and circle are joined by
lines indicating marriage or mating relationships. You must have at least 10 people on each pedigree.
Please review the pedigree shown below to understand how relationships may be indicated.
A. PICTURE OF A PEDIGREE: EXAMPLE ONLY!
The picture shows you one example of a pedigree family.
B. TRAITS TO FOLLOW:
1. Ear lobe attachment: The ear lobes may either hang free or be attached directly to the side
of the head. The gene for the free or unattached ear lobe trait is dominant (EE or Ee), while
attached earlobes are caused by having two recessive genes (ee).
2. Tongue rolling: Some people have the ability to roll their tongue into a distinct closed Ushape when they extend their tongue from their mouth. This ability to roll the tongue is due
to a dominant gene (RR or Rr). Those who have the two recessive genes (rr) can only curve
their tongue slightly.
3. Hitchhiker's thumb: People with two recessive genes (ss) for hitchhiker's thumb can bend
the distal joint of their thumb back so that it forms an angle of almost 45 degrees. This would
be hyperextension of the thumb. People with a dominant gene (SS or Ss) cannot do this and
could be called a straight thumbed person or close to it.
4. Mid-digital hair: The mid-digital hair trait is determined by a dominant gene (MM or Mm)
for each finger causing hair to grow on the middle joint of that finger. The trait is carried by a
set of five alleles and will cause hair to grow on one finger, two fingers, etc., depending on
what allele you inherit. People who have no hair on the digital part of their fingers carry all
recessive genes (mm).
5. Widow’s Peak: If you have Widow's Peak, a dominant gene (PP or Pp), your forehead
hairline will have a downward dip in it, as in a heart. Lift up the hair of your forehead to
check for this trait. People without widow's peak have a smooth hairline with no dip (pp).
Men starting to go bald (or already bald) may be unable to score this trait.
6. Thumb Crossing: In a relaxed interlocking of fingers, left thumb over right indicates the
dominant allele is present in either heterozygous or homozygous individuals (LL or Ll);
homozygous recessives naturally place the right thumb over the left (ll).
7. Toe Length: Individuals whose second toe is longer than the hallux (big toe) possess a
dominant gene (TT or Tt). Individuals with a longer hallux are recessive (tt).
8. Cleft Chin: A dimple or cleft in the center of the chin is a dominant gene (CC or Cc). No
cleft or dimple is a homozygous recessive (cc).
9. Freckles: Having multiple points of pigmentation in the skin is a dominant gene (FF or Ff).
Individuals without freckles are homozygous recessive for this trait (ff).
10. Ear Wiggling: Ability to move ears due to muscular contraction is a dominant gene
(WW or Ww). Individuals unable to move their ears are homozygous recessive (ww).
C. PROCEDURE AT HOME:
1. Take this lab home and using the table provided write the observed results for all ten of the traits
listed in Part A. Try to find as many relatives as you can, going back as many generations as you can
determine; for example, to great-grand parents. Once again, you must have at least 10 people for
each trait.
2. Next make four pedigree designs of your family for four of the traits listed in Part A. Title the
pedigree using the trait and letters and put your name on the top of the page. Draw each pedigree on
a separate piece of paper. If you have a relative you cannot find or who is unreachable, put a
question mark between the parentheses to the right of his/her name for that trait. (Only two people
from each pedigree can have question marks!)
1. In the blank below each person in the pedigree (circle or square), give your first name and the
first name of each of your genetic relatives.
2. In the parentheses to the right of the person's name, give what genotype you think he or she
has. [Example Joe (F__) or Jane (SS) or Sue (?)]
3. Remember, Part A is only a picture example listing the family pedigree design method. Your
actual family pedigree will vary.
4. If grandma or grandpa or Uncle George is out of town, try calling them on the weekend and
have them check their genetic traits for you. This is why I gave you the project really early,
so that you can contact your relatives.
5. If you are adopted or don't live with either genetic parent or if you cannot contact any of your
relatives for any reason, select a friend or neighbor and do his/her family pedigree instead of
yours.
6. ADDED BONUS POINTS (10 points): If your family has a very unusual trait, research its
mode of transmission (dominant/recessive) and do an extra pedigree to show how it has gone
through your family.
7. ADDED BONUS POINTS (5 points): For the person in the class with the most people on
the pedigree, with the most neat and presentable pedigree.
D. ANALYSIS AND INTERPRETATIONS: (MUST BE IN COMPLETE SENTENCES)
1. Do you think that anyone in the class has all of the same traits that you have? Why?
2. Using a Punnett square, what is the percentage for two of your traits that you inherited from
you parents? For example, if you did not inherit the tongue rolling allele (rr) from your
parents, what was the chance in percentages that you would not receive this trait? Explain.
3. Can you accurately determine one of your relative’s genotype by observing its phenotype?
Explain your answer.
4. What color are your eyes? If brown, hazel, and green are dominant (E) and blue is recessive
(e), what is your genotype for your eyes? Was it your mother, your father or both that gave
you your eye color? Explain how you know.