Heredity and Genetics
Your Genes:
Genes determine whether or not you possess certain physical traits. It is largely your genes that
determine if you are blue eyed or brown eyed, or have brown or blond hair. These traits are highly
complex, and involve the interaction of many genes. However, several traits are determined by
only one gene. Some examples of these simple traits are shown below.
For these simple traits only one gene is involved. But for this gene you have two copies or
versions of each gene. We call these gene versions alleles. You get one allele from your mother
and one allele from your father. Certain alleles are dominant, and you only need one of these to
give you a particular trait. Other alleles are recessive and you need to get that recessive allele
from both your mother and your father in order to have that trait. Dominant alleles are
represented as capital letters and recessive alleles as lower-case letters. Circle which alleles you
possess for each of the following traits.
Tongue Rolling: Can you roll your tongue into a U-shape? Try it. If you can, then you possess
the dominant allele and should circle "T-". If you can't roll your tongue, you have two recessive
alleles, and should circle "tt".
Tongue Rolling
Ttt
(circle one)
Attached Earlobes: Have a partner examine your earlobes. If they hang free at the bottom, you
are dominant (E-). If they are attached, you are recessive (ee).
Attached Earlobes
E-
ee
Interlocking Fingers: Fold your hands together by interlocking your fingers. Which thumb is on
top? If the left thumb is on top, you are dominant (I-). If the right thumb is on top, you are
recessive (ii).
Interlocking Fingers
Iii
Dimples: Dimples are a dominant trait (D-). If you don't have dimples, you are recessive (dd).
Dimples
D-
dd
Gender: Males possess a "Y" chromosome and should circle XY. Females possess two "X"
chromosomes and should circle XX.
Gender
XY
XX
Bent Little Finger: Look at the little finger on each hand. If they bend in toward your ring finger,
you have the dominant gene.
Bent Little Finger
Lll
Widow's Peak: If your hairline is shaped in a downward "V", then you are dominant for that gene
(W-).
Widow's Peak
W-
ww
Lesson adapted from The University of Arizona (http://student.biology.arizona.edu.sciconn)