Download GENETIC TRAITS

GENETIC TRAITS
GOAL: Learn about the basic definitions regarding genetics (genotypes) and
inherited traits (phenotypes), as well as about the role of DNA in determining
traits.
MATERIALS:
• Multi-colored popsicle sticks, labeled with dominant and recessive alleles
• Dragon baby worksheets; one per student
• Human traits worksheet; one per group
VOCABULARY:
• Allele: The form (or identity?) of a gene/genes having a known trait
• DNA (deoxyribonucleic acid): The genetic material of all living organisms
(including strawberries!)
• Gene: The basic unit of heredity.
• Genotype: All of the inherited genes in an organism.
• Phenotype: Observable traits of an organism.
• Dominant: Alleles for which having a single copy results in that trait being
observed.
• Recessive: Alleles for which having a single copy results in that train being
observed if the second copy is also recessive, or being hidden if the second copy
is dominant.
• Trait: A genetically determined characteristic
CLASS: Discussion (~ 5 minutes)
• What is a trait? Anything that identifies as both unique (e.g. hair color, eye color,
height) and human (e.g. face, one heart, brain)
• Where do people get their traits? These traits are encoded into our DNA, which we
get from our parents.
• How many genes are there for a trait? It depends, we have genes from both Mom
and Dad, but only certain genes get expressed and some traits require multiple
genes. We call these sets of genes, alleles.
• How do we know what trait we will have? We don’t, we only know what is definitely
possible by looking at our parents; these are phenotypes. To know for sure the
likelihood of having a trait, we have to know our genotype AND know which
alleles are dominant and which alleles are recessive.
EXPERIMENT ONE: Human Traits (~15 minutes)
1. For each trait listed, explain how to identify that trait (see attached sheet).
2. For each student, have them write in YES or NO under their name (one
worksheet per group).
3. Report the fraction that answered YES in your group.
4. Discuss whether or not the trait is dominant or recessive.
EXPERIMENT ONE: How to Identify Traits
Trait
Description
Dominant or
Recessive?
Bent pinky
Hold out hand, look at top (distal) segment of Dominant
pinky. Does it bend inward toward the ring finger?
Tongue rolling
Can you roll your tongue into a tube shape? Dominant
Homozygous recessives are non-rollers and
cannot learn to roll their tongues.
Widow’s Peak
V-shaped hairline (can be subtle, just look to see Dominant
if there is a ‘point’ in the middle of the forehead).
Attached
ear
Recessive
lobes
Homozygous
recessives
have attached ear lobes.
Hitchhiker’s
thumb
Can you bend the distal joint
of the thum backward to
nearly a 90deg angle?
Recessive
Thumb crossing
On the count of three, clasp your hand together,
with fingers overlocking. Is your left thumb over
your right thumb?
Small indentation of the skin, commonly located in
cheeks and chin.
Is your second toe longer than your big toe?
Is your hair curly? Wavy? Straight?
Dominant, left
over right
Dimples
Short big toe
Curly hair
PTC taster
Dominant
Dominant
Curly, DD
Wavy, Dd
Straight, dd
Place the Phenylthiocarbamide (PTC) paper on Dominant
your tounge. Does it taste bitter?
EXPERIMENT TWO: Dragon Babies (~30 minutes)
Adapted from: Dragon Genetics Protocol
1. Have all the students pair up (does not have to be boy/girl, but each pair will have
a male and female popsicle stick).
2. Each student picks up five Popsicle sticks, one of each color.
3. Start with one color stick (allele) and have each student drop his or her stick onto
the table. The side of the stick that is up gets passed on to the baby. Record the
results for each color in the allele. Note: A CAPITAL LETTER = DOMINANT
allele, while lower case letter = recessive allele. Example for PURPLE
ALLELE (BODY) is shown below.
BABY GENOTYPE (Step 4):
MOM
DAD
BABY PHENOTYPE
(Step 5):
G
G
GREEN BODY
r
R
ORANGE SPOTS
t
T
SPOTS ON BACK ONLY
4. Use the decoding chart on the board to figure out the phenotype associated with
your baby’s genotype and write phenotype into chart.
5. Once students have correctly written in a Phenotype, pass out one dragon sheet
per student and color in/draw a Dragon Baby.
6. Share results with the group/class; discuss the prevalence of dominant, mixed, or
recessive traits.
GENOTYPE TO PHENOTYPE DECONDING CHART
Popsicle Stick Allele
Green Writing
Red Writing
Blue Writing
Purple Writing
Black Writing
Dominant
A. Spikes along spine
B. No tail spike
D. No eyelids
E. Round eyes
F. Fangs
H. External ear
J. Brown horn
G. Green body
R. RR – red spots, Rr – orange
spots
T. Spots on back only
X. Fire breathing
Y. Male
Recessive
a. No spikes along spine
b. Tail spike
d. Eyelids
e. Almond eyes
f. No fangs
h. Internal ear
j. Yellow horn
g. Purple body
r. Rr – organge spots; rr –
yellow spots
t. Spots on back & wings
x. Non-fire breathing