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INVESTIGATING INHERITED TRAITS OF AN UGLY BABY
INTRODUCTION
Heredity is the passing on of traits, or characteristics, from parent to offspring. The units
of heredity are called genes. Genes are found on the chromosome in the cell. The
combination of genes for each trait occurs by chance.
When one gene is stronger than the other gene, the trait of the second gene is masked or
hidden. The stronger gene is the dominant gene. The gene that is hidden is the recessive
gene. Dominate genes are written as capital letters and recessive genes are written as
lower case letters. If both genes are the same, that is either both capital or both lower
case, the trait is said to be pure. Some other terms for this are purebred, homozygous, and
homeogenus. If the genes are not the same, that is one is capital and one is lower case, the
trait is said to be hybrid, heterozygous, or heterogeneous-most of the time. Some traits
can blend instead of one gene being stronger than the other. This is called incomplete
dominance. The genetic makeup of an individual is their genotype. What the trait looks
like is the phenotype. In humans, the sex of an individual is determined by the male gene.
Individuals with the genotype XX are females and XY are males.
PURPOSE
In this investigation students will observe how the results of different gene combinations
produce different phenotypes. The students will be exposed to inheritance patterns that
are governed by Mendel’s Principles. Each pair of students will assume the role of
mother and father.
SAFETY
Caution students about throwing coins.
MATERIALS
1 coin of type per group of 2 students
Copies of worksheets
PROCEDURES
1. If the gender of both individuals in your group is the same, flip the coin to see
who will assume the opposite role.
2. Who ever is the father flip the coin to determine the gender of the baby. If the
coin lands head up, the baby is female. If it lands tails up, it is a boy. There is no
need for the mother to flip since she can only offer an X chromosome. Write
the gender (boy or girl) in the phenotype box on your lab sheet. In the Genotype
box, write XX or XY, which ever is the case.
3. Each member of the group will flip the coin once to determine the genotype of
their half of the gene pair (allele). Two alleles together make a gene pair.
HEADS IS ALWAYS CAPITAL(DOMINANT) AND TAILS IS ALWAYS
LOWERCASE (RECESSIVE)
4. Note which letter you are to use with each trait and notice that the letter changes
with each trait.
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5. As you go through the traits, be sure to write both the phenotype and genotype
on your lab sheet. Phenotype will always be a word and genotype will always be
letters.
6. When you come to a double letter such as hair and eye color each person will
flip the coin two times. These are examples of traits that are made of more than
one gene pair.
7. When you have completely filled out your lab sheet. Look at the second trait,
shape of face to see which face shape your baby has. When you have
determined this, ask your teacher for the correct shape.
8. Draw your baby using the phenotypes on your lab sheet. Another words, if your
baby is HH for curly hair, then your drawing should have curly hair. You can
look at the pictures for help. Notice which traits are truly dominant and
recessive and which ones blend, like hair texture.
9. Some traits are controlled by more than one pair of genes. We call these
polygenic traits. Examples of polygenic traits are skin color, eye color, and hair
color. Use the following instructions for determining these traits:
Dark is dominant over light, to determine the genotype flip the coins for two
complete sets then look the phenotype up on the chart below.
SKIN COLOR
AABB
AABb
AAbb
AaBB
AaBb
Aabb
aaBB
aaBb
aabb
very dark brown
dark brown
light brown
dark tan
EYE COLOR
medium tan
light tan
AABB
beige
AABb
light beige
AAbb
ivory
AaBB
AaBb
Aabb
HAIR COLOR
aaBB
aaBb
AABB
black
aabb
AABb
black
AAbb
red
AaBB
dark brown
AaBb
brown
Aabb
strawberry blonde
aaBB
light brown
aaBb
blonde
aabb
light blonde
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nearly black
dark brown
brown
green with brown flecks
green
hazel (brownish or grayish green)
grayish blue
blue
light blue
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DATA SHEET
Student Name___________________________
Partner Name___________________________
Class Period____________Date____________
TRAIT
GENOTYPE
PHENOTYPE
Gender
Shape of face
Cleft in chin
Hair type
Widow’s Peak
Spacing of eyes
Shape of eyes
Position of eyes
Size of eyes
Length of eyelashes
Shape of eyebrow
Position of eyebrow
Size of nose
Shape of lips
Size of ears
Size of mouth
Freckles
Dimples
Skin color
Hair color
Eye color
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Questions:
1. Would you expect the other pairs of students in your class to have an offspring
similar to yours?
Explain.________________________________________________________
_________________________________________________________
_________________________________________________________
2. If a man who has long eyelashes (LL) marries a lady who has long eyelashes (Ll),
what are the possible genotypes and phenotypes of their children?
Genotypes_________________
Phenotypes________________
3. What are the possible genotypes of the parents of a child who has wavy hair
(Hh)? ________________
4. Which traits in the investigation showed blending of genes? ______________
________________________________________________.
This is called _________ dominance.
5. Can the actual traits of the offspring be determined by knowing the traits of the
parents? Expalin.__________________________________________
6 . A woman received the genes aBcD from her mother and AbCd from her father.
Which of the following gene combinations could be present in her gametes:
ABCD, abcd, ABCDD, aBccD, ABcd, AaBb. Circle the correct answer(s).
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TEACHER ANSWER SHEET
1. Would you expect the other pairs of students in your class to have an offspring
similar to yours? Explain. The chances are not good that another group would flip
for the same phenotypes for all of the characteristics.
2. If a man who has long eyelashes (LL) marries a lady who has long eyelashes (Ll),
what are the possible genotypes and phenotypes of their children?
Genotypes LL, L1
Phenotypes: only long
3. What are the possible genotypes of the parents of a child who has wavy hair
(Hh)? HH and Hh, or HH and hh or Hh and Hh or Hh and hh
4. Which traits in the investigation showed blending of genes? Hair, spacing of eyes,
size of eyes, size of nose, shape of lips, size of ears, hair color and eye color
This is called incomplete dominance.
5. Can the actual traits of the offspring be determined by knowing the traits of the
parents? Explain. No, you would have to know the genotypes to determine for
sure.
6 . A woman received the genes aBcD from her mother and AbCd from her father.
Which of the following gene combinations could be present in her gametes:
ABCD, abcd, ABcd, AaBb. Circle the correct answer(s).
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