Download Genetics Packet - Lakeland Regional High School

Name: _______________________
Date: ________
Genetics Packet Practice Problems
Part 1: A Dog Called Spot
Imagine this microscopic drama: a sperm cell from a male dog
fertilizes an egg cell from the female dog. Each dog’s gamete contain 39 chromosomes
and the zygote (which will eventually develop into a puppy) will have a total of 78
chromosomes, one set from the mother and one from the father.
Chromosome
From Mother
Chromosome
From Father
L
h
a
T
l
H
a
t
Two of the puppy’s chromosomes are shown above. It is a homologous pair because each
chromosomes contains alleles (versions of a gene) that code for the same traits. One of the
chromosomes in the pair came from the mother and one came from the father.
The only difference between the two is that one may have a dominant allele (capital letter) and
the other a recessive allele (lower case) for a given trait. To have a dominant trait the puppy
only needs to have one copy of the dominant allele. However, to have a recessive trait, they
puppy must have both copies of the recessive allele.
Using the chromosomes above, the chart below, and your vocabulary list to answer the following
questions.
TRAIT
Hair Length
Hair Texture
Hair Curliness
Coat Pattern
DOMINANT
Short = L
Wiry = T
Curly = H
Spotted = A
RECESSIVE
Long = l
Silky = t
Straight = h
Solid = a
a. What is the texture of the puppy’s coat? How do you know? Explain.
b. What is the texture of the father’s coat? How do you know? Explain.
c. What is the texture of the mother’s coat? How do you know? Explain.
d. What is the pattern of the puppy’s coat? How do you know? Explain.
e. Is the pattern of the puppy’s coat the same as pattern of the parent’s coat? How
do you know? Explain.
f. Does either parent have curly hair? Which one(s)? How do you know? Explain.
g. List the traits for which the puppy is homozygous. Tell the genotype (letters) and
the phenotype (the trait/appearance).
h. List the trait for which the puppy is heterozygous. Tell the genotype (letters) and
the phenotype (trait).
i. Based on the information provided in this scenario, why can’t you completely
describe the puppy’s parents even though you can accurately describe the puppy?
I. Dominant Recessive Traits
1. Cystic fibrosis (CF) is an inherited chronic disease that affects the lungs and
digestive systems of about 30,000 children and adults in the United States. A
defective gene causes the body to produce unusually thick, sticky mucus that clogs the
lungs and leads to life-threatening lung infections and obstructs the pancreas. It is
recessive trait, meaning you only show signs of the disease if you’ve inherited two
recessive alleles from your parents.
Jennifer and Tim are a young married couple planning a family. Tim’s younger sister had
CF and died before she finished high school. It is possible Tim carries the gene for CF.
They have decided to have genetic tests before trying to conceive in order to determine
whether they could have a child affected by the diseases. The couple received their
test results and was devastated to find out that they are both carriers. Carriers are
people who have one cystic fibrosis allele and one normal allele. They are not affected
by the disease, but have a chance of giving it to their child.
Perform a Punnett Square below to predict the probability that Jen and Tim’s
children will have CF. What is the probability that their child will have CF?
Jennifer:
Note: Use ‘D’ for the healthy allele
since it is dominant over ‘d’ the
cystic fibrosis allele.
Egg
Egg
Sperm
Tim:
Sperm
Write a sentence that answers the question from above. The first sentence
has been done for you.
There is a 25% chance that their child will inherit Cystic Fibrosis
2. Huntington's Disease is a devastating, degenerative brain disorder for which
there is, at present, no effective treatment or cure. Huntington’s slowly diminishes
the affected individual's ability to walk, think, talk and reason. Eventually, the person
with the disease becomes totally dependent upon others for his or her care. Signs of
the disease don’t usually show up until age 30 or 40. However, Huntington’s disease
is a dominant trait- which means you only need to inherit one copy of the allele
to have the disease.
Sheila does not show any signs of having Huntington’s disease right now. Sheila’s
father does have the disease, even though his mother does (grandma Lucy) does not
have the disease. Sheila’s mother is healthy and does not have Huntington’s disease.
What is Sheila’s probability of having the gene for Huntington’s and therefore
developing the disease later in life?
Note: use ‘H’ for the Huntington’s allele & ‘h’ = healthy allele.
Complete the chart below for Huntington’s disease and finish with a one sentence
written response to the original question.
Mother:
Genotype Ratio:
Egg
Egg
Phenotype Ratio:
Sperm
Father:
Sperm
Write a sentence that answers the question from above.
_____________________________________________________________
3. Hypercholesterolemia is a disorder that causes excess cholesterol in the blood
and heart disease. This disorder is caused by a dominant allele. If each of your
parents had the disorder and had 12 children, how many of those children will not
have the disorder? Hint: it is possible for these parents to have a child without
the disorder. Show your work in the punnett square below. (assume both
heterozygous)
Mother:
Egg
Egg
Genotype Ratio:
Sperm
Phenotype Ratio:
Father:
Sperm
Write a sentence that answers the question from above.
4. Black hair is dominant to blonde hair. A man marries a woman and they have 24
kids; 18 of them have black hair and 6 have blonde hair. What is the genotype of
the dad? Mom? What is the probability of these two individuals having a child
heterozygous for black hair? Heterozygous for blonde hair?
Mother:
Egg
Genotype Ratio:
Egg
Sperm
Phenotype Ratio:
Father:
Sperm
Sentence to answer questions: ______________________________________
_____________________________________________________________
_____________________________________________________________
5. A woman who has freckles and black hair, had a father without freckles and had
blonde hair. The woman marries a man who is heterozygous for freckles and black
hair. What is the probability of having a child with freckles and blonde hair?
Mother:
Egg
Mother:
Egg
Egg
Sperm
Father:
Egg
Sperm
Father:
Sperm
Sperm
Sentence to answer questions: ______________________________________
_____________________________________________________________
II. Incomplete Dominance Traits
6. If traits are inherited through incomplete dominance, then they can be a blend
of one another. For example, mixing a red rose and white rose makes a pink rose.
Cross a pink rose and a white rose. What is the probability that the offspring will
be heterozygous?
Mother:
Genotype Ratio:
Egg
Egg
Sperm
Phenotype Ratio:
Father:
Sperm
Write a sentence that answers the question from above.
_____________________________________________________________
7. Human’s hair type is an example of Incomplete Dominance. If you have either
of the two possible homozygous combinations for hair type, then you either have
straight hair, or curly hair. If you are heterozygous then you have wavy hair.
Develop a punnett square problem for hair type where you have a genotypic ratio
of 1:2:1. Then complete the problem.
Mother:
Egg
Genotype Ratio: 1:2:1
Egg
Sperm
Phenotype Ratio:
Father:
Sperm
Write a sentence that answers the question from above.
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
III. Codominance
8. Codominance is just like incomplete dominance, except that the trait doesn’t
show up like a blend. In incomplete dominance, a white chicken and a black chicken
would make a gray one (WB), but in CODOMINANCE, a white chicken and a black
chicken make a black and white spotted chicken (WB).
In your own words define the term codominance: ____________________________
_______________________________________________________________________
9. Cross a white–and-black feathered chicken with another white-and-black
feathered chicken? Draw the square. What’s the chance of getting a white-andblack chicken?
Mother:
Genotype Ratio:
Phenotype Ratio:
Egg
Sperm
Father:
Sperm
Egg
Write a sentence that answers the question from above.
_____________________________________________________________
10. Horse hair color is codominant as well. White horses can breed with Red
horses and make roan horses. Based off of your understanding of codominance,
what would a roan horse look like?
____________________________________________________________
Perform a cross between a two roan horses. Draw the square. What is the
probability that the offspring will be white?
Mother:
Genotype Ratio:
Phenotype Ratio:
Egg
Egg
Sperm
Father:
Sperm
Probability White:
Codominance: Blood Types
There are many different ways to classify blood types, but the most common
blood type classification system is the ABO (said "A-B-O") system. There are
four types of blood in the ABO system: A, B, AB, and O. These blood types refer
to different versions of a carbohydrate molecules, complex sugars, which are
present on the surface of red blood cells. People with Type A blood have Type A
carbohydrate molecules, people with Type B blood have Type B carbohydrate
molecules, and people with Type AB blood have both Type A and Type B
carbohydrate molecules on their red blood cells. People with Type O blood do not
have either the A or B carbohydrate molecules on their red blood cells.
The Type A and Type B carbohydrate molecules are called antigens because they
can stimulate the body to produce an immune response, including antibodies.
Antibodies are special proteins that travel in the blood and help our bodies to
destroy viruses or bacteria that may have infected our bodies. Normally, our
bodies do not make antibodies against any molecules that are part of our own
bodies. For example, people with Type A blood do not make antibodies against the
Type A (carbohydrate) antigen which is present on their red blood cells, but they
do make antibodies against the Type B (carbohydrate) antigen.
Test your understanding of blood groups by completing the table below.
Blood Group
Antibodies in
plasma for which
blood type?
AB
A
B
B
O
Blood group A
If you belong to the blood group A,
you have A (carbohydrates)
antigens on the surface of your red
blood cells and antibodies in your
blood to fight off type B
(carbohydrates) antigens.
Blood group B
If you belong to the blood group B,
you have B (carbohydrates) antigens
on the surface of your red blood
cells and antibodies in your blood to
fight off type A (carbohydrates)
antigens.
Blood group AB
If you belong to the blood group
AB, you have both A and B
(carbohydrates) antigens on the
surface of your red blood cells and
no antibodies in your blood to fight
off type A and B (carbohydrates)
antigens.
Blood group O
If you belong to the blood group O,
you have neither A nor B
(carbohydrates) antigens on the
surface of your red blood cells, but
you have antibodies in your blood to
fight off BOTH A and B
(carbohydrates) antigens.
What about the Rh factor?
The Rh factor genetic information is also inherited from our
parents, but it is inherited independently of the ABO blood type
alleles. There are 2 different alleles for the Rh factor known as
Rh+ and Rh-. Like the ABO blood type RH+ will result in a Rh
carbohydrate (antigen) located on the outside of the cell were a
RH- will result in no carbohydrate (antigen).
Rh factor Possible genotypes
Someone who is "Rh positive" or "Rh+" has at least one Rh+ allele, but
could have two. Their genotype could be either Rh+/Rh+ or Rh+/Rh-.
Someone who Rh- has a genotype of Rh-/Rh-. Just like the ABO
alleles, each biological parent donates one of their two Rh alleles to
their child.
+
Rh+/Rh+
Rh+/Rh-
Rh-
Rh-/Rh-
Rh
Mother Father
Child
Rh-
Rh+
Rh+
Rh-
Rh-
Rh-
A mother who is Rh- can only pass an Rh- allele to her son or daughter. A father who is Rh+
could pass either an Rh+ or Rh- allele to his son or daughter. This couple could have Rh+ children
(Rh- from mother and Rh+ from father) or Rh- children (Rh- from mother and Rh- from father).
Blood transfusions — who can receive blood from whom?
If you are given a blood transfusion that does not match your blood type, antibodies present in
your blood will react with the antigens present on the donated red blood cells. For example, if a
person who has Type A blood is given a Type B blood transfusion, then this person's anti-B
antibodies will react with the Type B antigens on the donated red blood cells and cause a
harmful reaction. This reaction can cause the donated red blood cells to burst and/or clump
together and block blood vessels. This type of transfusion reaction is illustrated in the
following drawing.
Transfusion reactions can be fatal. To prevent this from happening, doctors test whether a
person's blood is compatible with the donated blood before they give a transfusion. The
general principle is that a person can be harmed by donated blood if it has blood cells with an
antigen that can react with the antibodies that the person has in his or her blood, since this will
produce a transfusion reaction.
j. Test your understanding of blood groups by completing the table below.
Blood Group
Antigens on
Antibodies
red blood cells in plasma
A+
A & Rh+
B
A-
A
B & Rh+
B+
B & Rh+
B-
B
AB+
A and B & Rh+
AB-
A and B
O+
Rh+
O-
None
Can give
blood to
Can receive
blood from
A+ and AB+
A+/- and O+/-
11. Which blood type would you say could be called a universal receiver of any blood type?
12. Which blood type would you say could be called the universal donor to any blood type?
13. If a man who is blood type AB is in an accident and is in need of a blood transfusion,
which parent or parent’s (Earnst - A, Denise - B, Michael - AB or Danielle - B) would be
able to donate blood to this individual? Explain.
Genetics of Blood Types
Your blood type is established before you are born, by specific genes inherited from your
parents. You receive one gene from your mother and one from your father. These two genes
determine your blood type by causing the presence or absence of the Type A and Type B
antigen molecules on the red blood cells.
The blood type gene has three different versions or alleles: IA, IB, and i. i represents the allele
for type O blood and is recessive. IA, IB represents the alleles for blood type A and B and they
are both dominant. Since everybody has two copies of these genes, there are six possible
combinations:
IA IA and IA i - both resulting in Type A blood,
IB IB and IB i - both resulting in Type B blood,
IA IB - resulting in Type AB blood,
i i - resulting in Type O blood.
These combinations are called genotypes, and they describe the genes you got from your
parents.
Father
(Type AB)
Sperm
Each biological parent gives one of their two ABO alleles to their child. For example, a mother
who is blood type O has genotype ii and can only give an i allele to her son or daughter. A father
who is blood type AB could give either an IA or a IB allele to his son or daughter. This couple
could have children of either blood type A (i from mother and IA from father) or blood type B (i
from mother and IB from father). This is illustrated in the Punnett square below.
Mother
(Type O)
Eggs
i
i
A
A
I
I
IA
i
i
B
B
B
I i I i
I
14.If Michael Jr. grows up and marries a woman with blood type O, what is the probability of
him and his wife having a child with blood type O? Let’s say that Michael Jr. is heterozygous
for his blood type.
Genotype Ratio:
Mother:
Phenotype Ratio:
Egg
Egg
Sperm
Father:
Sperm
Write a sentence that answers the question from above.
_____________________________________________________________
15.If a universal donor marries a universal receiver what is the probability of them having a
child that is a universal donor or receiver?
Mother:
Genotype Ratio:
Phenotype Ratio:
Egg
Egg
Sperm
Father:
Sperm
Write a sentence that answers the question from above.
_____________________________________________________________
16.A person that is heterozygous for blood type A marries a man that is homozygous dominant
for blood type B. They both want to have children and really want to have a child that is a
universal receiver. As a friend who knows about genetics explain to them if they can have a
child that is a universal receiver and why they can or cannot.
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
IV. Sex-Linked Traits
17. Hemophilia is a genetic disease in which the victim’s blood does not clot well,
leading them to problems when they get cuts. They can easily lose too much
blood, and even a bruise can lead to serious internal bleeding. Hemophilia is a
Sex-Linked Recessive Disease. Cross a carrier female with a normal male. Fill in
the chart, and answer the questions below.
Mother:
Egg
Egg
XH
Xh
Sperm
XH
Father:
Sperm
Y
Offspring’s Genotype
Offspring’s Phenotype
(trait)
Percent of offspring
Male Hemophiliac
Normal Male
Female Hemophiliac
Normal Female
Based on the Punnett Square, how many of the sons have Hemophilia? _____________
How many of the daughters are normal? _________________________
How many of the daughters are carriers? __________________________
Can a male be a carrier for a sex-linked trait? Explain. _____________________________
_____________________________________________________________________
______________________________________________________________________
Mother:
18. Muscular Dystrophy is a disease that causes people to lose function of their
muscles, and can die from it. It is a Sex-linked Recessive trait. Cross a female
who has MD with a normal male, then fill in the chart.
Egg
Egg
Sperm
Father:
Sperm
Offspring’s Genotype
Offspring’s Phenotype
(trait)
Percent of offspring
Mother:
19. Color Blindness is a sex-linked recessive trait. Cross a male
who is color blind
with a homozygous dominant female. What is the probability that the male
offspring will be colorblind?
Egg
Egg
Sperm
Father:
Sperm
Sentence: ____________________________________________________
20. Hemophilia is a disease characterized by an individual whose blood does not
clot properly. Hemophiliac’s blood takes a very long time to clot, and in many
cases, hemophiliacs can die from internal or external bleeding. Hemophiliacs can
take pills that contain “clotting factors”, which are proteins that plug up bleeds in
your body. Hemophilia is a sex-linked recessive disorder. Roberta carries the
gene for hemophilia, and marries Jim, who is a hemophiliac. Circle all of the
statements that are true.
a. All of their children will be hemophiliacs
b. Half of their children of both sexes will be hemophiliacs (based on probability)
c. All of their female children will be hemophiliacs
d. Half of their female children will be carriers
e. 25% of their male children will be normal
V. Going further
After taking biology class, you realize that you want to pursue an
education and career in biology. You study genetics and ecology in college,
and wind up studying tree frogs in Peru. You discover a new species of
tree frog, and name it Kelly’s Tree Frog, after the teacher who first
influenced your decision to pursue a career in biology. You notice that the
frogs are capable of having orange spots on their back and legs, or yellow
spots on their back and legs. You are interested in the pattern of inheritance for spot color, so
you start to track the parent frogs and their offspring. You follow a family of frogs, and find
that the one parent has orange spots, and the other has yellow. After they breed, you are only
able to find four of their offspring, three of which are yellow, and one of which is orange.
21. Based on the phenotypes of the parents, and the phenotype ratio of the offspring, how is
this trait (spots) inherited? Explain.
_____________________________________________________________
22. The same parents produce another clutch (group) of offspring, the following spring season.
This time you track 33 of the frogs, and find that 16 have yellow, and 17 have orange. Based on
the phenotypes of the parents, and the phenotype ratio of the offspring, how is this trait
(spots) inherited? Explain.
_____________________________________________________________
23. What could explain the difference in phenotype ratios from the first group of offspring to
the second in the question above? Which group should you use to draw your conclusion?
24. You bring males and females with both yellow and orange spots back to your lab to
investigate the genetics of spot color further. After breeding many combinations of mates, you
find that two yellow-spotted frogs will always produce yellow-spotted offspring. As for orangespotted frogs, you find that sometimes two orange spotted parents produced only orangespotted children, while other times orange spotted frogs could produce some yellow-spotted
offspring. Based on all the information you know, what conclusion can you draw about how spot
color is inherited? Explain.
25. A fellow biologist, Sandy, works with you in Peru. She breeds a yellow frog with an orange
frog, and finds that half the offspring are orange, and half are yellow. She exclaims, “Maybe
the trait is sex-linked. One color could be dominant, and the other could be recessive.” You
reply, “Give me some time, and I will let you know.” How would you go about testing whether the
trait is Sex-linked or not?
How would you test to see if Sandy’s prediction was right? (Hint: You can distinguish a male
Kelly’s Tree Frog from the female because the male has little spurs, or boney hooks, near their
ankles, for mating, while females do not.)
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
Make up your own ending to the story by writing a conclusion sentence. For example, because
the cross between a ________ male and a _______ female produced _________ offspring, I
conclude that color spot is inherited ____.
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
26. All of the above problems aimed to answer the question,
“What is the probability that offspring will have a certain
trait?” Well, what if we wanted to answer the question,
“What is the probability that offspring will have two traits
together?” For example, “What is the probability that my
child will have brown eyes and Cystic Fibrosis?” To solve this,
you will have to perform a dihybrid cross. What the %&*$#
is that, you ask? It is simple. All you have to do is multiply
the probability of one outcome with another. Let’s try.
The media won’t tell you the real reason that Brad Pitt and Angelina Jolie prefer to adopt
children, rather than conceive their own. You see, everyone thinks that they are so lucky
because of their fame, fortune. But buried beneath their good looks are devastating genes.
Unfortunately, Brad Pitt is heterozygous for Thalassemia, a disorder that results in anemia.
Anemia refers to any disease that causes the body to make fewer than normal healthy red
blood cells. Some of his cells are normal, some are ineffective. Thalassemia is codominant,
meaning the most severe version of the disease occurs if an individual receives two copies for
the Thalassemia gene, but a heterozygous individual will show symptoms as well (just not as
severe).
To make matters worse, Angelina is heterozygous for Sickle Cell Anemia, which causes
her red blood cells to be half-moon shaped, not round. Sickle cell anemia is also a recessive
disorder, but in the heterozygous condition displays codominant properties. In other words,
having two copies of the gene for either disease results in the most severe anemia, while only
having one copy of the gene will result in moderate anemia.
Long story short, Angelina and Brad visit a geneticist because they are interested in
having biological children (instead of adopting). The geneticist tells them that if their child was
to inherit a gene for Sickle Cell from Angelina, AND a gene for Thalassemia from Brad, then
the child will have severe, and possibly even life-threatening anemia. (None of this is true)
27. What are Brad and Angelina’s chances of having a baby who is BOTH heterozygous for
Thalassemia AND heterozygous for Sickle Cell? Show the Punnett Square(s)
28. Why would being heterozygous for both Sickle cell and Thalassemia be so dangerous?
What do you think the symptoms/dangers would be?
29. Angelina Jolie has a Widow’s Peak, like the picture to the right. Brad has no
Widow’s Peak, as his hairline is straight. Widow’s Peak is dominant to straight
hairline. If Angelina is heterozygous for Widow’s Peak, what is the probability
that Brangelina’s kids will have NO form of anemia, and STRAIGHT hairline.
Show the crosses.