Download Heredity and Genetics

Heredity and Genetics
Purpose: This lesson is designed to provide students with a general understanding of
simple genetics and heredity.
Grade Level: The lesson is best suited to students who have had some background in
cell biology. Students who are not developmentally capable of abstract thought may have
a hard time understanding the concepts of genes and heredity. However, even very young
students can appreciate the fact that those around them are different, and that we get our
traits from our parents. They may not be able to understand the little letters assigned to
the genes, but they will still have fun comparing their traits with others. We did the lesson
for an eighth grade class and it proved very successful.
Materials: The only materials you will need are:
1. The worksheet provided here (print it out!)
2. PTC and Sodium Benzoate taste strips (available from Carolina Biological Supply,
2700 York Road, Burlington, NC 27215, 800-334-5551, very cheap, instructions
included)
NOTE: You can do the lesson without the taste strips.
Lesson prepared by Science Connector Bill Binder
Student Worksheet
The University of Arizona
Determining Your Genes:
Did you know that your genes determine whether or not you possess certain physical
traits? Well, they do. It's your genes that make you 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, and if you have the gene
then you have the trait.
You have two genes for every trait. You get one from your mother and one from your
father. Certain genes are dominant, and you only need one of the pair to give you its trait.
If you don't have a dominant gene, then you are recessive for that trait. Dominant genes
are represented as capital letters and recessive genes as lower-case letters. Circle which
genes 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 gene and should circle "T-". If you can't roll your tongue, you have
two recessive genes, and should circle "tt".
Tongue Rolling
T-
tt
(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
I-
ii
Dimples: Dimples are a dominant trait (D-). If you don't have dimples, you are recessive
(dd).
Dimples
D-
dd
Sex: Males possess a "Y" chromosome and should circle XY. Females possess two "X"
chromosomes and should circle XX.
Sex
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
L-
ll
Double Jointed Thumb: If you have double jointed thumbs, you have the dominant
gene.
Double Jointed Thumb
J-
jj
Freckles: If you have freckles then you have a dominant gene (F- ). If you don't have
freckles then you are recessive (ff).
Freckles
F-
ff
PTC Taste: Chew a taste strip. Some people can taste PTC, and others cannot. If the
strip tastes bitter to you, you are a "taster" and have the dominant gene for this trait (P-).
If the strip doesn't taste like anything, you are recessive (pp). 70% of the people in the
United States are "tasters". Is anyone in the room a "non-taster"??
PTC Taste
P-
pp
Sodium Benzoate Taste: Different genes determine if you can taste sodium benzoate. If
it tastes salty, bitter, or sweet to you, then you have the dominant gene (S-). If you don't
taste anything, you are recessive (ss).
Sodium Benzoate Taste
S-
ss
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
Teacher Notes
The University of Arizona
http://student.biology.arizona.edu/sciconn