Human Heredity Lab
Although human DNA is 99.9% the same, the 0.1% difference in our DNA
account for differences in hair, skin and eye color, height, etc., In this lab,
we will be using Mendel’s Laws of dominance and recessiveness to identify
individual phenotypes, and, when possible, individual genotypes for ten
human traits. The traits that we will look at, unlike most human traits, have a
tendency to follow Mendel’s laws of simple dominance and recessiveness.
We will conclude the lab by determining the frequency of these traits among
the members of the class.
11.
Data Chart & Analysis
Phenotype is the appearance of an organism. Genotype is the actual genetic code
for traits. Keep in mind that the traits listed describe the tendency of how they
appear and are transmitted. There can be exceptions to these general rules.
Individual Data
Trait
Lab Directions
1.
Determine your phenotype for the following human traits that
follow simple Mendelian inheritance. Record your data on the
chart, as well as the class analysis chart.
2.
Determine if your earlobes are attached or unattached. Attached
earlobes are attached directly to the side of the face while
unattached earlobes appear to be lobed. Unattached earlobes are
dominant, E to attached, e.
3.
Having hair on the middle joint of the hand, M is dominant over
not having mid-digital hair, m. Look for the presence of hair or
hair follicles above the middle joint of the fingers.
4.
Having freckles on the face, F is dominant to not have freckles.
5.
A cleft chin means that you have a dimple in the middle of your
chin. Even small ones count! A cleft chin, C is dominant, d to
having a rounded chin.
6.
If the back of your thumb forms a smooth curve when you bend
it back, then you have a hitchhikers thumb. A hitchhikers thumb
is recessive, s, to having a straight thumb, S.
7.
Try to roll your tongue into a distinct U-shape. Tongue rollers
carry a dominant, R.
8.
Put your hands together as if holding your own hands with your
fingers interlocking each other. If you placed your left thumb on
top or your right thumb, you carry a dominant allele, L. If you
placed your right thumb on top, you carry two recessive alleles.
Try to interlock your hands in the opposite way.
9.
Having dimples on the face is dominant, D, to not having
dimples, d.
10.
Have a big toe that is shorter than the second toe, B is dominant
to having a big toe that is longer than the second toe.
Look at your hairline on your forehead. Hair that is attached
straight across the forehead is recessive, w, to hair that is
attached in a distinct V-shape, known as a Widow’s Peak, W.
Phenotype
Genotype
Class Data
Dominant
Recessive
Total
#
%
dominant
%
recessive
Earlobe
Mid-digital
hair
Freckles
Cleft Chin
Hitchhikers
Thumb
Tongue
Roller
Hand clasp
Dimples
Big Toe
Hairline
Questions:
1.
If a trait is classified as a dominant trait, does that mean it
shows up in more people in the population? Use the data
above to justify your answer.
2.
Two people who can roll their tongues have a child who
cannot roll his tongue. Use a cross between the two
individuals to explain why.
3.
A woman heterozygous for freckles marries a man without
freckles. What is the likelihood their children will have
freckles?