Date ______
Human Traits Lab
Name ________________
Introduction
Heredity is the passing of traits or characteristics from parents to offspring. The units of heredity are
called genes. Genes are found on the chromosomes in a cell. The combinations of genes for each trait
occur by chance.
An alternate form of a gene is called an allele. For example, if the gene is height, the two alleles are tall
and short. When one allele in a pair is stronger than the other allele, the trait of the weaker allele is
masked, or hidden. The stronger allele is the dominant and the allele that is masked is the recessive allele.
Dominant alleles are written as capital letters and recessive alleles are written as lowercase letters. If both
alleles in a pair are the same, the trait is said to be homozygous, or pure. If the alleles in a pair are not
similar, the trait is said to be heterozygous, or hybrid. Sometimes alleles are neither dominant nor
recessive. The result of such a situation is a blending of traits in the heterozygous condition.
The genetic makeup of an individual is known as its genotype. The observable physical characteristics of
an individual that are the result of its genotype are known as its phenotype. In humans, the sex of an
individual is determined by the particular combination of the two sex chromosomes. Individuals that have
two X chromosomes (XX) are females; those with an X and a Y (XY) are males. In this investigation,
you will observe how the results of different allele combinations produce certain traits.
Problem: How are traits inherited?
Procedure:
1. Determine which partner will toss for the female and which will toss for the male. Remember that
there are two alleles per trait.
2. Have the partner who is representing the male flip a coin into the well to determine the sex of the
offspring. If the coin lands head up, the child is a female. If tails, a male. Record the sex on the
sheet.
3. For all the coin tosses you make, HEADS will represent the DOMINANT allele and TAILS the
RECESSIVE.
4. You and your partner should now flip your coins into the well at the same time. NOTE: the coins
should be flipped only once for each trait except for hair color, eye color and skin color.
5. Continue to flip, record the allele for mother and father, the combination of alleles and the
phenotype for each trait in the appropriate boxes on the Data Table.
6. Using the recorded traits, both of you draw the facial features for your offspring on the face
template sheet. You can also use an online face generator, such as http://flashface.ctapt.de/, but
you will still have to color in the face.
Date ______
Human Traits Lab
Name ________________
Data Table
Parents Names ___________________________ and _________________________
Child’s Name ____________________ Sex _________________________
#
Trait
1
Face Shape
2
Cleft Chin
3
Hair Type
4
Widow’s Peak
5
Eyes (Distance Apart)
6
Eyes (Shape)
7
Eyes (Slantedness)
8
Eyes (Size)
9
Lower Lip
10
Color of Eyebrows
11
Nose Shape
12
Ear Attachment
13
Length of Eyelashes
14
Shape of Eyebrows
15
Position of Eyebrows
16
Size of Nose
17
Shape of Lips
18
Size of ears
19
Size of Mouth
20
Freckles
21
Dimples
22
Eye Color
23
Hair Color
24
Skin Color
Allele From
Mother
Allele From
Father
Genotype
Phenotype
Draw YOUR OFFSPRING on the face template. Remember to include all 24 traits in your child.
Date ______
Human Traits Lab
Name ________________
Analysis and Conclusions
1. What percent change did you and your partner have of “producing” a male offspring? Explain your
answer. _______________________________________________________
_____________________________________________________________
2. Would you expect the other pairs of students in your class to have an offspring similar to yours?
Explain. _______________________________________________________
_____________________________________________________________
3. What is the difference between a genotype and a phenotype? ________________________
_____________________________________________________________
4. Most traits in this lab followed a dominant and recessive pattern. For example RR and Rr both give
your child a round face, but rr gives a square face. Which traits in this investigation did not follow
this pattern, but showed a blending of genes? _________________________________
_____________________________________________________________
Critical Thinking
Looking at the meiosis
diagram to the right, the
chromosomes contain the
gene for baldness. Bald is
the dominant trait and
therefore represented by a
“B,” and normal hair is
recessive, “b.”
Use the diagram to answer
the following questions:
5.
________
__________________________________________________________
Looking at the alleles on the chromosomes, is this person bald? How can you tell?
6. Which cells represent diploid cells and which cells represent haploid cells? Explain how you can
tell the difference between haploid and diploid cells. __________________________
___________________________________________________________
Date ______
Human Traits Lab
Name ________________
7. What is the name of the structure formed by the chromosomes in cell B? How many chromatids
does this structure contain?__________________________________________
8. How many alleles for each gene does the sperm cell contain? ____________________________
9. What percentage of sperm cells carry the allele for baldness?
_____________________
10. Explain how passing down alleles from one generation to the next is like flipping a coin.
___________________________________________________________
___________________________________________________________
___________________________________________________________