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Take Home Lab:
What Are Some Traits in Your Family?

Donald Galen
1994 Woodrow Wilson Collection


Introduction

This lab should follow the study of pedigree designs and human genetics. Four pedigree designs will be prepared of your family's genetics. You will construct the pedigree representing two, three, or four generations. The traits that you will follow are: ear lobe attachments, tongue rolling, hitchhiker's thumb, and mid-digital hair. Begin at the bottom of the pedigree design with you and your genetic brothers and sisters. A square is used to represent a male person and a circle a female. 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. Please review the pedigree shown to understand how relationships may be indicated.

A. PICTURE OF A PEDIGREE:

The picture shows you one example of a pedigree family.

B. PROCEDURE AT HOME:

Take this lab home and make four pedigree designs of your family for the traits listed in Part C. You may go back as many generations as you can determine; for example, to great-grand parents. Draw each pedigree on a separate 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.

  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 (Ff) or Jane (SS) or Sue (?)]

  3. Remember, Part A is only a picture example listing the family pedigree design method and 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.

  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: If your family has a very unusual trait, do an extra pedigree to show how it has gone through your family.

C. TRAITS TO FOLLOW:

  1. Ear lobe attachment: (See Fig. 1) 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 (F), while attached earlobes are caused by having two recessive genes (ff).

  2. Tongue rolling: (See Fig. 2) Some people have the ability to roll their tongue into a distinct U-shape when they extend their tongue from their mouth. This ability to roll the tongue is due to a dominant gene (R). Those who have the two recessive genes (rr) can only curve their tongue slightly.

  3. Hitchhiker's thumb: (See Fig. 3) 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 (S) cannot do this and could be called a straight thumbed person or close to it.

  4. Mid-digital hair: (See Fig. 4) The mid-digital hair trait is determined by a dominant gene (M) for each finger causing hair to grow on the top 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).

D. PICTORIAL VIEW OF PART C:


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