Download Human Traits Lab - Education Service Center, Region 2

Human Traits
Lab
The characteristics that an organism
inherits from its parents are called
traits. In humans, traits include the
color of a person's hair, skin, and eyes,
the blood group, the shape of the nose
and lips, and the tendency to be shortsighted or bald. Some of the traits that
humans acquire can be modified by
the environment, while others cannot.
Traits are usually considered to be
dominant or recessive. In a dominant
trait, only one allele is necessary to see
the trait. In a recessive trait, both
copies of the allele must be present to
see the trait.
Procedure
1. Take a look at the human traits
listed on your paper.
2. For each trait, write down which
one you express (have).
3. Write whether it is dominant or
recessive and a possible genotype.
dimples or no dimples
dominant
DD or Dd
recessive
dd
straight or curved thumb
dominant
SS or Ss
recessive
ss
rolling or non-rolling tongue
dominant
RR or Rr
recessive
rr
unattached or attached earlobes
dominant
UU or Uu
recessive
uu
widow’s peak or straight hairline
dominant
WW or Ww
recessive
ww
bent or straight pinkies
dominant
BB or Bb
recessive
bb
cleft or no cleft chin
dominant
CC or Cc
recessive
cc
Procedure
4. Total up how many dominant traits
you have
5. Total up how many recessive traits
you have
Fill in the table on your paper
Create a bar graph using the class data
Genes determine traits. An allele is a
form of a gene. Each gene has at least
two alleles. Each allele may occur in
one of two forms, either dominant or
recessive. Complete the following to
practice understanding how scientists
work with alleles. Most traits are the
result of several genes, but we will
practice with some that are thought to
be controlled by a single gene.
PART 1: Symbolizing Alleles
In the table, several traits are listed. The two
forms of the gene are listed. Scientists use two
forms of the same letter to represent the two
alleles.
A dominant allele is represented by a capital
letter. A recessive allele is represented by a lower
case letter. If there is a capital letter, it is usually
written first.
For each trait, use the letter in parenthesis. The
first one has been done for you as an example.
PART 1: Symbolizing Alleles
PART 2: Determining the Phenotype
Genes have at least two alleles. There are
three possible combinations (genotype) of
alleles in each pair. If a dominant allele is
present, the dominant trait will appear in the
organism. In order for a recessive trait to be
expressed, both alleles of the gene pair must
be recessive.
In the table, identify what trait will be seen.
The trait that can be seen is called a
phenotype. The first example has been done
for you.
PART 2: Determining the Phenotype
PART 3: Determining the Genotype
The genotype refers to the alleles in the gene
pair. There are three possible combinations. If
an organism expresses a dominant trait, there
are two possible genotypes. If the organism
expresses a recessive trait, there is only one
genotype possible.
Fill in the table with the possible genotypes for
each phenotype. The first one has been done
for you.
PART 3: Determining the Genotype
complete the multiple choice questions
and turn it in.