Download Human Traits Lab

Mrs. Keadle
JH Science
Name__________________________________ period _____
date assigned_____________ date due ______________ date returned _____________
Human Traits Lab
Introduction
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 short-sighted 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 in the table below.
2. For each trait, circle which one you express.
3. Answer the questions that follow.
Trait
Dominant
Recessive
Dimples
No Dimples
Straight Thumb
Curved Thumb
Possible
Genotype
Dimples
D
Thumbs
C
Rolling Tongue
R
Rolling Tongue
Non-Rolling Tongue
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Human Traits Lab
Mrs. Keadle
Trait
Dominant
Recessive
Unattached
Attached
Widow's Peak
Smooth Hairline
White Forelock
No White in Hair
Bent pinkies
Straight Pinkies
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Possible
Genotype
Ear Lobes
U
Hairline
S
White Forelock
W
Pinky Fingers
B
Data
1. How many recessive traits did you exhibit?____________________________________
2. How many dominant traits did you exhibit?____________________________________
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Human Traits Lab
Mrs. Keadle
JH Science
Class Data
# of students in
class exhibiting the
trait
Trait
# of students in
class exhibiting the
trait
Trait
Dimples
No Dimples
Straight Thumbs
Bent Thumbs
Rolling Tongue
Non-Rolling
Tongue
Unattached
Earlobes
attached Earlobes
Widow’s Peak
Straight Hairline
White Forelock
Non-White Forelock
Bent Pinky Fingers
Straight Pinky
Fingers
Create a bar graph using the class data.
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Number of Students with
the Trait (by twos)
22
20
18
16
14
12
10
8
6
4
2
Straight Pinky
Fingers
Bent Pinky
Fingers
Non-white
Forelock
White Forelock
Straight
Hairline
Widow’s Peak
Attached
Earlobes
Unattached
Earlobes
Non-Rolling
Tongue
Rolling
Tongue
Curved Thumb
Straight
thumbs
No Dimples
Dimples
0
Dominant and Recessive Human Traits
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Human Traits Lab
Mrs. Keadle
JH Science
Genes determine traits. An allele is a form of a gene. Each gene occurs in pairs. Each gene may
occur in one of two forms, either dominant or recessive alleles. 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 below, 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.
Complete the table:
trait
handedness (R)
dominant expression
symbol
right handed
hair line (W)
widow’s peak
straight hairline
ear lobes (F)
free (unattached)
attached
hand folding (L)
left thumb on top
right thumb on top
chin features (C)
cleft chin
no cleft
toes (S)
second toe longer than big toe
second toe shorter than big
toe
R
recessive expression
symbol
left handed
r
PART 2: Determining the Phenotype
Genes come in pairs. 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 below, identify what trait will be seen. The trait that can be seen is called a phenotype.
the first example has been done for you.
Genotype
RR
ww
FF
cc
Tt
Ss
Ll
Phenotype (what you can see)
the person will be right handed
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Human Traits Lab
Mrs. Keadle
JH Science
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 below with the possible genotypes for each phenotype. The first one has been done
for you.
Genotype
RR or Rr
Phenotype (what you can see)
the person will be right handed
left handed
widow’s peak
straight hairline
attached ear lobe
free earlobe
right thumb on top
left thumb on top
cleft chin
no cleft
second toe shorter than big toe
second toe longer than big toe
55 An offspring inherited a dominant allele from one parent and a recessive allele from the other
parent for the same trait. Which of the following is a possible explanation for what will be
exhibited by the offspring for that trait?
A The offspring will exhibit the recessive trait with the dominant trait being masked.
B The offspring will exhibit the dominant trait with the recessive trait being masked.
C The offspring will not exhibit that trait because the dominant and recessive traits he received
will each mask the other.
D The offspring will combine the recessive allele with the dominant allele and exhibit an
entirely new trait.
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Human Traits Lab
Mrs. Keadle
56 The ability to roll your tongue is an inherited
trait. There are more people who can roll
their tongues than people who can’t roll
their tongues. Which of the following could
be a correct assumption to explain this?
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58 Different forms of a gene are called
A mutations
B alleles
A The ability to tongue roll is a rare trait.
C chromosomes
B The ability to tongue roll is a recessive
trait.
D phenotype
C The ability to tongue roll is a dominant
trait.
D The ability to tongue roll is a submissive
trait.
57 Why does a person who inherits an
allele for curly hair and an allele for
straight hair have curly hair?
A The allele for curly hair is recessive.
B The allele for curly hair is dominant.
C The allele for straight hair is
dominant.
D The allele for curly hair is inherited
from both parents.
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Human Traits Lab