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Packet #12 – Mendelian Genetics Summer 2014
This Activity Packet belongs to:
_________________________
At the end of the unit you will turn in this packet. Record the completion due dates in the chart below.
You should expect a variety of quizzes: announced, unannounced, open-notes and closed-notes.
If this packet is LOST, please: drop it off at the BHS Science Dept. (rm 365) OR
drop it off in Ms. Brunson’s classroom (rm 351) OR
call the Science Dept. at (617) 713-5365.
Packet
page Activity
Points
Earned Available
Human Genetic Traits 5
Chances' Choices 14
Probability and Genetics (plus notes) 14
Notes: Patterns of Inheritance --- ---
Solving Genetics Problems 15
Mendelian Genetics Test Review 5
Total
What is Genetics?______________________________________
____________________________________________________
____________________________________________________
____________________________________________________
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Human Genetic Traits
Introduction: It does not matter what animal or plant you examine, virtually no two individuals of a
species are exactly alike. Every individual of a species has variations; variations are the product of genes
being passed from parent to offspring. For example, pea plants can vary in the color of their seeds,
carnations vary in the color and size of their flowers, gorillas vary in the wrinkles on their nose, and bears
can vary in the thickness and length of their coats. These are, in no way, the only variations between
individuals of these species, they are one in ten, hundreds, or thousands of variations.
What is the source for the variations we observe between and within species? Life is intimately linked to
molecular interactions. Is there a molecule that is responsible for the biological variations that we can
observe? How is it possible that a single molecule could code for biological differences?
In this journal, you will have the opportunity to examine some of the many variations within a single
species... humans. Using the biology class as a sample population, you will identify a few of the many
variations. Upon completion of the activity, you will take a few selected traits to determine your genetic
number and find your biology class twin or triplet or maybe quadruplet.
Pre-activity questions: (Do NOT use a book. Instead, answer with what you THINK you know!)
1. What are genes made of?
2. What do genes do?
3. How much of your DNA came from your biological Mother? From your biological Father?
4. How much of your DNA do you share with siblings (if you have them)?
5. Name 2 variations you get from DNA and 2 variations that don’t come from DNA.
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Procedure:
1. Your teacher will guide you through the list of traits. First, circle your version for the trait.
2. Next, compile the class frequency for each trait (in percentage).
Trait
Variation #1 Variation #2
Variation Class frequency
(%) Variation
Class frequency
(%)
Gender Male Female
Tongue Rolling Yes No
Cheek Dimples Yes No
Earlobe Ends Attached Free
Chin Cleft Yes No
Freckles Yes No
Hair color Dark Light
Widow’s Peak Yes No
Hair curl Straight Nonstraight
Eye Color Non-blue Blue
Color Vision Normal Color-blind
Finger Interlocking Right on top Left on top
Mid-digit finger hair Yes No
Hitchhiker’s thumb Yes No
PTC taster Yes No
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Chances' Choices
1. How to read a pedigree:
= =
=
=
=
Paul and Stacy:
2. What is state-mandated testing of newborns? Give some examples of diseases tested for.
3. What is PKU? Below is a schematic of what happens in this disease. Describe the symptoms.
4. Describe dominant vs. recessive traits and genotypes.
5. Explain why it makes sense that PKU is recessive (at a molecular level).
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6. Do Frank and Alan have the gene for this enzyme? _____
7. Do Frank and Alan carry the allele that causes PKU?
a. Let’s review meiosis (spermatogenesis in Paul):
Before After Metaphase I
Interphase Interphase
Prophase II Metaphase II
Sperm cells
b. What are Paul and Stacy’s genotypes? Remember – they each have TWO copies of this gene
________ x ________
c. Which alleles could be in Paul’s sperm? How many copies of this gene will go into the sperm?
____ or ____
d. Which alleles could be in Stacy’s eggs? How many copies of this gene will go into the egg?
____ or ____
e. Using a Punnett square to make predictions:
f. What fraction of Paul and Stacy’s children do we expect to have PKU? ________
g. What are the chances of Paul and Stacy having another child with PKU? ________
8. What does each row or column in a Punnett square represent? ___________________
9. What does each individual box represent? ____________________
P
p
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Scene 2: Will Alan ever play for the Celtics?
10. What is an X-linked trait?
11. How do you show an X-linked trait in a genotype?
12. What is hemophilia?
13. What are the chances of Paul and Stacy have a child with hemophilia AND PKU?
Parent's genotypes: _________ x _________
Paul Stacy
Chromosomes in metaphase I of Meiosis:
Paul: Stacy:
OR OR
Gametes: ______, ______, ______, ______ ______, ______, ______, ______
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Too complicated? Another way to do it using probability:
PKU: Hemophilia: Sex:
Multiply fractions to get overall probability!
So...
A. What are the chances of Paul and Stacy having a child with hemophilia AND PKU?
B. What are the odds of an individual child being a boy?
C. What are the chances of having a girl with hemophilia?
D. What are the chances of having a girl that is a carrier of hemophilia and a carrier of PKU?
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Probability and Genetics
Introduction: If someone flips a coin, you know that there are two possible outcomes: heads or tails.
You can predict how likely either is to happen. Can you make similar predictions about the outcomes of
genetic events? In this activity, you will use biological data to explore the concept of probability.
Probability is a mathematical tool that enables us to make predictions. We will provide you with
information about the offspring of two rabbits, and you will look for patterns in the results. This activity
is an altered version of “Game of Chance” on page 420 of the BSCS textbook.
Pre-Journal Discussion:
Genes and alleles
Genotypes and Phenotypes
Heterozygous and Homozygous
Law of Dominance
Procedure: (2 pt)
1. When flipping a coin, what is the probability, in percent, that a single coin toss will result in
heads? In tails?
2. Why is a coin toss a good way to represent allele combinations that occur in nature?
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Materials: one penny per student
Procedure:
1. Solve the following problems. (1 pt)
a. A pair of rabbits mated and produced 10 offspring. How many males and how many females
would you predict are in those offspring? (statistically – not a guess) (Fill into table below)
b. Even if you are reasonably confident that your prediction is correct, can you guarantee how
many males and females will be born in the litter? Explain your answer.
2. Test your prediction by using a coin to simulate the sex of the 10 offspring. (1 pt)
3. Look at the data below – these show the results of 3 rabbit matings. (2 pt)
Small sample size
Trial # of offspring Males Females
1
2
3
10
10
10
4
6
6
6
4
4
a. Do these results match your predictions or test results from step 1?
4. Next investigate the relationship between probable outcomes, actual results, and sample size.
Examine the data below. Note that the total number of offspring is 600. Calculate the percentage of
male rabbits for each group of 600 offspring. Record these results in the table. (Percentage males =
[(# males) / (# total offspring)] x 100)
Large sample size
Trial # of offspring # Males # Females % Males
1
2
3
600
600
600
279
296
316
321
304
284
5. Answer the following questions: (2 pt)
a. Are these results generally closer to 50 percent than those in the small sample size (step 3)?
b. Based on your observation, what effect does sample size have on the match between probable
outcomes and actual results?
Predicted Actual
Heads (girls)
Tails (boys)
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Analysis and Discussion: (1 pt each)
1. Use what you have learned about the importance of sample size (number of trials) to evaluate the
following medical study reported in a local newspaper.
“A study reported in a medical journal Acta Artifacta appears to link ownership
of fast cars with premature balding. The study, consisting of 17 men who own
sports cars, found that nearly 70 percent suffered from premature balding. The
authors of the study conclude that because this percentage of balding is much
higher than in the general population, there is an increased chance of suffering
from premature baldness if one owns a fast car.”
2. If you flip a coin five times and get heads every time, what is the probability that you will get tails
on the next flip?
3. Restate the following accurately: One out of every two offspring that results from a cross between
parents with the Genotypes Hh and hh definitely will have Huntington’s disease. [Hint:
Huntington’s disease is a dominant trait]
4. Evaluate the following claims. Who is right? Explain.
Marcia – “I really think we should have another child. I know we already have 5 boys, but I’ve
always wanted a little girl. Since I’ve had 5 boys already, probability says that I am overdue for a
girl. I am much more likely to have a baby girl this time.”
Tom – “We have enough children already. Plus, you are no more likely to end up with a girl this
time than any other time. You could end up with 6 boys and then where would we be!?!”
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Probability and Genetics Notes
What role does probability play in genetics?
Sample size?
Accuracy of predictions?
What does meiosis have to do with inheritance?
(Law of Segregation)
How is variation guaranteed in offspring?
a.
b.
c.
Why do we use Punnett Squares?
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Types of Inheritance Notes
Simple Dominance
Incomplete Dominance (and an example)
Codominance (and an example)
Polygenic traits (and an example)
There are 3 alleles for blood type: ____, ____, ____.
The blood types (and their genotypes) are:
Type A blood: _______ or _______
Type B blood: _______ or _______
Type AB blood: _______
Type O blood: _______
Blood type is determined by which _______________ you have on your blood cells
If you are missing a certain antigen, the body develops ____________________ that attack that
antigen if they encounter it.
Type A blood has antibodies against _______ antigens
Type B blood has antibodies against _______ antigens
Type AB blood has antibodies against ______ antigens
Type O blood has antibodies against ______ antigens
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Solving Genetics Problems
When doing genetics problems, you should always: write all answers (neatly) on a separate piece of
paper. Number the problems and show all work/ explain your reasoning.
Mendelian Genetics – you should know: Law of Segregation, Law of Dominance, Law of Independent
Assortment, dominant, recessive, homozygous, heterozygous, genotype, phenotype, how to set up symbols,
the meaning of a Punnett square, probability.
Rules of probability:
Rule of multiplication
Rule of addition – not used often in genetics
Show all of your work on a separate piece of paper. Remember to use a strategy when you solve problems:
i. Establish an __________________.
ii. Write the parental ________________.
iii. Figure out what _____________ each parent can make.
iv. Set-up a Punnett Square.
v. Answer the stated question(s).
Simple Dominance
1. Long eye-lashes are dominant over short eye-lashes. Cross a heterozygous long eye-lashed mother with a
homozygous long eye-lashed father. What is the chance that these parents will have a long eye-lashed
offspring?
2. Normal skin is dominant over albino (the absence of pigment). Cross an albino mother with a heterozygous
father. What is the chance that these parents will have an albino child? What is the chance that these parents
will have an albino son?
3. If two animals heterozygous for a single trait are mated and have 200 offspring, about how many offspring
would you predict to have the dominant phenotype?
4. A male and a female, each with free earlobes (a dominant trait), give birth to a daughter with attached earlobes
(a recessive trait).
a.) If the couple has three more children, what is the chance that ALL of them will also have attached
earlobes?
b.) If the couple then has one more child (the first three are already born), what is the chance that this child
will also have attached earlobes?
c.) What is the chance that this fourth child will be a BOY with attached earlobes?
Alternate forms of inheritance
5. Suppose that red and white show incomplete dominance in a certain kind of flower. You cross a red flower
with a white flower. What percentage of the offspring do you expect to be pink? If you were to cross two of
these pink flowers, what ratios of color would you expect to see in the next generation?
6. Incomplete dominance is seen in the inheritance of hypercholesterolemia. Mack and Toni are both
heterozygous for this characteristic, and both have elevated levels of cholesterol. They give birth to a daughter,
Zoe, with a cholesterol level 6x higher than a “normal level,” and Zoe can be assumed to be homozygous for
this trait. If Mack and Toni have one more child, what is the probability that the child will suffer from the more
serious form of hypercholesterolemia seen in Zoe? (CL = low cholesterol, CH = high cholesterol)
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7. Redraw this pedigree and label the genotypes of everyone. If this couple has a fourth child, could it have blood
type B? Explain.
type A type B
type AB type A type O
8. Use the following table to answer the next question:
Phenotype/
Blood Type
Genotype Antibodies in the
blood
A
B
AB
O
IAIA or IAi
IBIB or IBi
IAIB
ii
Anti-B
Anti-A
None
Anti-A and Anti-B
What are the possible blood types of children born to the following couples? (You do not need to draw a
Punnett Square for each, but be careful to consider ALL possibilities!)
a.) type A female, type A male c.) type A female, type O male
b.) type B female, type AB male d.) type AB female, type AB male
Independent Assortment (Crosses with two or more traits)
Remember!
When dealing with 2 traits, a genotype has FOUR letters, representing 2 copies of each gene (example –
AaBb).
When a person makes a sperm or egg (gamete), they put one copy of EACH gene in the gamete. This
means the gamete would contain TWO letters (one of each).
You can set up a large 4x4 Punnett square (like we did with Chance’s Choices) or you can use multiple 2x2
Punnett squares and use the rules of probability.
9. In seeds, corn can be either yellow (Y) or purple (y). Seed texture can be either smooth (S) or wrinkled (s).
Suppose a heterozygous plant is crossed with a plant that is homozygous dominant for color and heterozygous
for texture. What percent of the offspring will be yellow and wrinkled?
10. Bill and Barbara both have freckles, and Barbara has a widow's peak while Bill has a straight hairline. They
give birth to a daughter, Sarah, has no freckles and a straight hairline. Freckles and a widow’s peak are both
dominant, whereas no freckles and no widow’s peak are both recessive.
a.) What is Bill's genotype? What is Barbara's genotype?
b.) What is the chance that they will give birth to a second child with freckles and a widow's peak?
c.) What is the chance that they will have a boy with freckles and a widow's peak?
11. In the animal called ipsywoodles,
B=black fur F=forked tongue H=hairy body N=normal wings L=long bristles
b=yellow fur f=plain tongue h=normal body n=straight wings l=short bristles
If you crossed a heterozygous black furred, plain tongued, homozygous hairy bodied, heterozygous normal
winged, heterozygous long bristled ipsywoodle (phew! – try saying that ten times fast!), with the same type of
ipsywoodle, how many of the offspring would have: (don’t even think about trying a large Punnett Square
here…use multiple smaller Punnett squares…)
a.) black fur, forked tongue, hairy body, normal wings, long bristles
b.) black fur, plain tongue, hairy body, normal wings, short bristles
c.) yellow fur, plain tongued, hairy body, straight wings, long bristles
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X-Linked Traits (Like Hemophilia in Chances’ Choices)
12. Red-green color blindness is a sex-linked trait, carried on the X chromosome. Why are there more color-blind
men than color-blind women?
13. Hemophilia is a disease caused by a recessive gene on the X chromosome. In a family, there are the following
children: 2 hemophiliac boys, a normal boy, a hemophiliac girl, and a normal girl. Draw a pedigree for this
family. What must the genotypes of the parents be? What is the genotype of each child?
Pedigrees:
14. Using the pedigrees below, predict the genotypes for all family members. For pedigree A, assume the shaded
trait is dominant and for pedigree B, assume the shaded trait is recessive. (Remember that you cannot fill in the
genotype of a dominant individual unless you KNOW for sure what his/her genotype is - don't guess!) Write
the letters on the lines provided.
15. Draw a pedigree for a family showing two parents and four children as follows:
(a) make the 2 oldest children boys and the two youngest girls.
(b) label the marriage line and the children line
(c) label the individuals and the generations with numbers
(d) Indicate person II-2 has attached earlobes (a recessive trait)
(e) Fill in the genotypes and symbols to indicate the remaining family’s traits
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Vocabulary
Genotype
Phenotype
Allele
Dominant
Recessive
Homozygote
Heterozygote
Autosome
Sex chromosomes
Crossing over
Homologous
Chromosomes
Quest Outline for Mendelian Genetics
1. What is the relationship between sample size and accuracy of prediction?
2. Explain the different causes of variation, including when they occur (mutations, independent
assortment, crossing over, random fertilization).
3. Define each of Mendel’s Laws (Law of Dominance, Law of Independent Assortment, Law of
Segregation) and give a concrete example of each.
4. Be able to solve genetics problems, including:
a. 1 trait Punnett squares (2x2)
b. 2 or more trait Punnett squares using probability
c. Incomplete dominance & co-dominance
d. Blood typing
5. What is the relationship between meiosis, fertilization, and chance of
inheritance?
6. What is crossing over and when does it occur?
7. What is the relationship between genetics and environment?
8. What patterns would you see in a pedigree for a trait that is:
a. Autosomal Dominant?
b. Autosomal Recessive?
c. Sex-linked Recessive?