Download MA STATE Frameworks: (This is what the state of

Name: ________________________________ Date: ____________ Class: ______
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2009-2010 CP2 GENETICS UNIT PACKET
FOR COMPLETE DOMINANCE
MA STATE Frameworks: (This is what the state of MA says you need to be able to do on your MCAS test)
Broad Concept: Genes allow for the storage and transmission of genetic information. They are a set of instructions
encoded in the nucleotide sequence of each organism. Genes code for the specific sequences of amino acids that
comprise the proteins that are characteristic of that organism.
3.3 Explain how mutations in the DNA sequence of a gene may or may not result in phenotypic change in an
organism. Explain how mutations in gametes may result in phenotypic changes in offspring.
3.4 Distinguish among observed inheritance patterns caused by several types of genetic traits (dominant, recessive,
incomplete dominance, codominant, sex-linked, polygenic, and multiple alleles).
3.5 Describe how Mendel’s laws of segregation and independent assortment can be observed through patterns of
inheritance (such as dihybrid crosses).
3.6 Use a Punnett Square to determine the probabilities for genotype and phenotype combinations in monohybrid
crosses.
Name: ________________________________ Date: ____________ Class: ______
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GENETICS: COMPLETE DOMINANCE (10.1-10.2)
Exploring Life concept 10.1: Genetics developed from curiosity about inheritance
Exploring Life concept 10.2: Mendel discovered that inheritance follows rules of chance
TOPICS:
o
o
o
o
Mendel
Monohybrid cross
Test Cross
Dihybrid cross
OBJECTIVES:
Date:
_________ 1. Describe the methods Mendel used in his plant-breeding experiments
_________ 2. Tell what the F in F1 and F2 stand for and what the P in “P generation” stands for.
_________ 3. Describe Mendel’s 3 laws
_________ 4. Predict the possible offspring of a monohybrid cross by using a Punnett Square
and calculate the probability of each type (genotype and phenotype) being born.
_________ 5. Model a test cross to prove the genotype of a dominant individual.
_________ 6. Contrast genotype and phenotype
_________ 7. Predict the possible offspring of a dihybrid cross by using a Punnett Square.
KEY TERMS:
Allele: alternative form of a gene
Complete Dominance: inheritance pattern in which a heterozygote expresses the dominant
phenotype
Dominant: description of an allele in a heterozygous individual that appears to affect the trait.
Dihybrid Cross: crossing organisms differing in two characters
F1 generation: first generation of offspring from P generation
F2 generation: second generation of offspring from P generation
Genetics: the study of heredity
Genotype: an organism’s combination of alleles
Heterozygous: having different alleles for a gene
Homozygous: having the same alleles for a gene
Hybrid: offspring of two different true-breeding varieties
Law of Dominance: in every pair of contrasting traits, one trait is dominant
Monohybrid cross: mating of two organisms that differ in only one character
P generation: true-breeding parents
Phenotype: observable traits of an organism
Punnett Square: diagram showing the probabilities of the possible outcomes of a genetic cross
Name: ________________________________ Date: ____________ Class: ______
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Recessive: description of an allele in a heterozygous individual that does not affect a trait.
Test cross: mating of an individual of unknown genotype (but dominant phenotype) with an
homozygous recessive individual
NOTES: Mendel and Rules of Inheritance (10.1, 10.2)
Traits: A trait is a variation of a particular character
o Example: one plant might have the trait of red flowers, while another might have
the trait of yellow flowers.
Mendel’s Plant Breeding Experiments
 In the 1800’s, a scientist named Gregor Mendel applied an experimental approach to
study inheritance
 His work eventually gave rise to genetics: the study of heredity.
 For seven years, Mendel bred pea plants and recorded inheritance patterns in the
offspring. He found that parents pass on to their offspring packages of traits (today called
genes) that are responsible for inherited traits.

Mendel used garden pea plants because they….
o are small
o are easy to grow
o produce large numbers of offspring
o mature quickly
o can be cross or self-fertilized
o have many varieties available

Mendel studied seven traits:
o flower color (purple or white)
o seed color (yellow or green)
o seed shape (round or
wrinkled)
o pod color (green or yellow)
o pod shape (inflated or
constricted)
o flower position on stem
(terminal or axial)
o plant height (tall or short)
Name: ________________________________ Date: ____________ Class: ______

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Before he started…
o He allowed plants to self fertilize for many
generations to ensure true-breeding plants.
(offspring produced only one form of a trait – like,
only green pods, or only yellow pods)
o Mendel called the true-breeding plants the
parental generation (P)

o Parental generation were true breeding yellow and true breeding green
First Experiment:
o Cross-fertilize the P (parent)
generation (cross the pure
yellow with the pure green)
o Mendel called the offspring
of the P generation the first
filial generation (F1)
o (filial comes from the Latin
word for “son”)
o F1 generation were all
yellow

Second Experiment:
o Allow the F1 generation to
self-fertilize.
o Mendel called the offspring of the F1 generation the second filial generation (F2)
o F2 generation were yellow and green in about a 3:1 ratio.
Rules of Inheritance
 Parents transmit traits to their offspring.
 Forms of a trait are called alleles.
 Individuals have 2 alleles for each trait; one from each parent.
 The presence of an allele does not guarantee the expression of that trait.
Mendel’s 3 Laws of Heredity:
 Law of Dominance: In every pair of contrasting traits, one trait is dominant.
 Law of Segregation: The two alleles an organism has for a trait separate randomly when
gametes are formed. (during meiosis) Remember, an organism gets one allele from
Mom, and one from Dad!
 Law of Independent Assortment: Alleles for different traits are inherited independently of
each other (…Which means that inheriting one does not affect the chance of inheriting
the other…unless they are on the same chromosome)
Name: ________________________________ Date: ____________ Class: ______
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o Example: Just because you inherit blond hair does not mean that you will inherit
blue eyes.
Name: ________________________________ Date: ____________ Class: ______
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THE LAW OF DOMINANCE:
In every pair of contrasting traits, one trait is dominant.
THE LAW OF SEGREGATION:
The two alleles an organism has for a trait separate randomly when gametes are formed.
THE LAW OF INDEPENDENT ASSORTMENT:
Alleles for different traits are inherited independently of each other (…Which means that
inheriting one does not affect the chance of inheriting the other…unless they are on the same
chromosome)

Example: Just because you inherit blond hair does not mean that you will inherit blue
eyes.
Name: ________________________________ Date: ____________ Class: ______
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NOTES: Inheritance of Traits - Complete Dominance
(Concept 10.1, 10.2)
Homozygous / Heterozygous
 For each inherited character, an organism has two alleles for the gene controlling that
character (one from mom and one from dad)
 If the two alleles are the same, the individual is homozygous (or pure)
 If the two alleles are different, the individual is heterozygous.
Dominant / Recessive
 Dominant alleles are those that keep recessive alleles from showing up in the phenotype.
 Dominant traits are represented by UPPER CASE LETTERS (BB)
 Recessive traits are represented by lower case letters (bb)
 Only ONE dominant allele needs to be present for the organism to show that Trait (Bb) or
(BB)
 If an individual has the phenotype BB, he is called homozygous dominant, or pure
dominant for the trait
 If an individual has the phenotype Bb, he is called heterozygous dominant.
 To show the recessive phenotype, BOTH alleles present must be recessive (bb)
 This individual is called homozygous recessive.
 Example
 Mom: Brown hair (BB)
 Dad: Blond hair (bb)
o They can only have children that have BROWN hair (Bb)
Name: ________________________________ Date: ____________ Class: ______
WS: Punnett Square – Widow’s peak
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Name: ________________________________ Date: ____________ Class: ______
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Punnett Square 26: Offspring From Two Heterozygous Parents
Name: ________________________________ Date: ____________ Class: ______
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MONOHYBRID CROSS COMPLETE DOMINANCE
PRACTICE PROBLEMS #1
1. In fruit flies, long wings are dominant over short wings. (Use W and w)
a. What letter(s) is/are used for long wings?
__________
b. What letter(s) is/are used for short wings?
__________
c. What genotype and phenotype will each of the following have:
Genotype
phenotype
Pure dominant
___________
_____________________
Pure recessive
___________
_____________________
Heterozygous
___________
_____________________
d. What are the gametes of the pure dominant fly? ________________
e. What are the gametes of the pure recessive fly? ________________
f. What are the gametes of the heterozygous fly? ________________
g. Complete the Punnett square below for a cross between the pure dominant and the pure
recessive fly.
Possible genotypes of offspring: ___________________________
Possible phenotypes of offspring: _________________________
Name: ________________________________ Date: ____________ Class: ______
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2. In pea plants, purple flowers are dominant over white flowers. (Use P and p)
a. What letter(s) is/are used for purple flowers? __________
b. What letter(s) is/are used for white flowers?
__________
c. What genotype and phenotype will each of the following have:
Genotype
phenotype
Pure dominant
___________
_______________________
Pure recessive
___________
_______________________
Heterozygous
___________
_______________________
d. What are the gametes of the pure dominant plant? ________________
e. What are the gametes of the pure recessive plant? ________________
f. What are the gametes of the heterozygous plant? ________________
g. Complete the Punnett square below for a cross between the pure dominant and the
heterozygous plant.
Possible genotypes of offspring: ___________________________
Possible phenotypes of offspring: _________________________
Name: ________________________________ Date: ____________ Class: ______
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Should This Dog Be Called Spot???
A sperm cell from a male dog fuses with an egg cell from a female dog. Each dog’s
gamete carries 39 chromosomes. The zygote that results from the fusion of the
gametes contains 78 chromosomes – one set of 39 chromosomes from each parent.
One homologous pair of the zygote’s 78 chromosomes are shown below:
Each chromosome of the homologous pair contains alleles for the same traits. But
one chromosome may have a dominant allele and the other a recessive allele. Use
the drawings and the table to answer the questions.
1. Will the puppy have a spotted coat?
2. Does the female dog have a spotted coat? Explain.
3. Does the male dog have a spotted coat? Explain.
4. What will the texture of the puppy’s coat?
Name: ________________________________ Date: ____________ Class: ______
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5. Will the texture of the puppy’s coat resemble that of either of its parents?
Explain.
6. Will the puppy have curly hair or straight hair?
7. Does the female dog have curly hair?
8. Does the male dog have curly hair?
9. Define the term heterozygous.
10. For which traits is the puppy heterozygous?
11. Define the term homozygous.
12. For which traits is the puppy homozygous?
13. Explain why you cannot completely describe the puppy’s parents even though
you can accurately describe the puppy.
Name: ________________________________ Date: ____________ Class: ______
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NOTES: Probability (10.1, 10.2 -??)
PROBABILITY
• Probability is the likelihood of a specific event occurring
• An event is a possible outcome
• For example: When a coin is flipped, one possible event (outcome) is “heads” and
another possible event (outcome) is “tails.”
PROBABILITY FORMULA
•
Probability =
•
For Example: What is the probability of a single coin landing on heads?
# of one kind of event
# of all possible events
Probability =
_____ Heads (1)____
Tails or Heads (2)
= 1 out of 2 = ½ = 0.5 = 50%
INFLUENCE
• If two coins are flipped, the outcome of one coin does NOT predict or influence the
outcome of the other coin.
PRODUCT RULE
• The probability of two or more events occurring simultaneously is the product of their
individual probabilities.
•
For example: What is the probability of getting heads on both coins when two coins are
flipped together?
–
We calculated the probability of flipping heads once as 50% (or ½).
–
To calculate the probability of flipping heads twice, we multiply each probability
together:
•
Probability of getting heads on coin 1 x coin 2 = % chance
•
½ x ½ = ¼ = 25%
WHY THIS IS IMPORTANT
• The parents’ alleles are like two sides of a coin, and a child receives one allele from mom
and one allele from dad.
•
In meiosis, these alleles are segregated (separated) independent of one another, like
flipping a coin.
Name: ________________________________ Date: ____________ Class: ______
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WS: PROBABILITY PROBLEMS #1
1. A man and a woman are heterozygous for freckles. Freckles (F) are dominant over no
freckles (f). What are the chances that their children will have freckles? Draw a Punnett
square below to prove your answer.
2. A man heterozygous for a widow's peak (W) marries a woman with a straight hairline (w).
A widow's peak is dominant over a continuous hairline. What is the chance their children
will have a Widow’s peak? Draw a Punnett square below to prove your answer.
3. Look at problems 1 and 2 above. Assume the two people in both problems are the same
couple. What is the probability that this man and woman will have…
a. A child with freckles and a widow’s peak?
b. A child with freckles and no widow’s peak?
c. A child with no freckles and a widow’s peak?
d. A child with no freckles and no widow’s peak?
4. Suppose a pea plant has two alleles for flower-color, purple (F) and white (f). Purple is
dominant to white. If a plant with one purple allele and one white allele is mated to a plant
with two white alleles, what percentage of the offspring will have purple flowers? Draw a
Punnett square below to prove your answer.
5. The chance for the pea plants above also having yellow peas vs. green peas is 50%.
What is the chance of the above plants producing offspring that have yellow peas AND
purple flowers?
Name: ________________________________ Date: ____________ Class: ______
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WS: PROBABILITY PROBLEMS #2
Using the traits for dog fur listed below, answer the following questions.
1. If dogs with these two genotypes (Male: HH and Aa, Female: Hh and Aa) mate, what are
their chances of having puppies who have… (you will need to do TWO crosses… one for
HHx Hh and one for Aa x Aa)
a. Spotted, curly fur
b. Spotted, straight fur
c. Solid, curly fur
d. Solid, straight fur
2. If a male dog who is heterozygous for short hair and has straight hair and a female dog
who has long hair and is pure for curly hair breed, what are their chances of having a
puppy who has….
a. Short, curly fur
b. Long, curly fur
c. Short, straight fur
d. Long, straight fur
Name: ________________________________ Date: ____________ Class: ______
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NOTES: TEST CROSS
A test cross is used to determine the GENOTYPE of a PHENOTYPICALLY DOMINANT
individual by looking at the offspring it has already had with a RECESSIVE individual.
A test cross is two pretend matings on paper that look at the types of offspring an individual has
already had and compares it to the two possible outcomes of a mating between a phenotypically
dominant individual and a recessive individual.
There are ALWAYS two test crosses:
 One between the homozygous dominant individual with a recessive individual
 One between the heterozygous dominant individual with a recessive individual
One of the test crosses will show the genotype of the individual.
Sample Problem
 A male mouse with black fur is mated with a female mouse with white fur. Seven
offspring result, three black and four white. Black fur (B) is dominant to white fur (b). What
is the genotype of the father?
Sample Test Cross:
Genotypes
%
Genotypes
%
Phenotypes
%
Phenotypes
%
Name: ________________________________ Date: ____________ Class: ______
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Using Punnett Squares: Practicing Skills (Some Test Cross)
Show the results of the following crosses using Punnett squares and the information in the
accompanying figure above.
1. Heterozygous short hair x heterozygous short hair
2. Heterozygous tabby x stripeless
Name: ________________________________ Date: ____________ Class: ______
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3. Colorpoint x homozygous normal
4. Homozygous tabby x homozygous tabby
5. In order to determine the genes of a tabby cat, you could perform a test cross by crossing
it with a homozygous recessive cat. Show what the expected kittens would be if the tabby
is heterozygous and if the tabby is homozygous.
Heterozygous tabby x recessive stripeless:
Homozygous tabby x recessive stripeless:
Genotype and Phenotype of offspring:
Genotype and Phenotype of offspring:
6. If the above tabby cat had 12 kittens, 3 of whom were stripeless, could you determine
what its genotype is? If yes, what is it? If not, tell why.
7. If the above tabby cat had 12 kittens, none of whom were stripeless, could you determine
what its genotype is? If yes, what is it? If not, tell why.
Name: ________________________________ Date: ____________ Class: ______
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Test Cross Problems #1
1. Brown eyes (B) is dominant to blue (b). A mother with blue eyes and a father with brown
eyes have four children. Three with brown eyes, on with blue. What is the genotype of
each parent? Show your work.
2. In pea plants, purple flowers (P) are dominant to white (p). A purple-flowered plant is
crossed with a white-flowered plant and 37 offspring result, all with purple flowers. Show
your work and answer the questions below.
a. What is the genotype of the white flower?
b. What is the genotype of the purple flower?
3. In guinea pigs, black fur is dominant to brown. A male guinea pig with black fur is mated
with a female with brown fur. They have 26 baby guinea pits, 10 with brown fur and 16
with black. What is the genotype of each parent? Show your work.
Name: ________________________________ Date: ____________ Class: ______
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4. In dogs, having erect ears (E) is dominant to having droopy ears (e). A droopy-eared
male dog fathers a litter of puppies with an erect-eared mother. Eight puppies result,
seven erect eared dogs and one droopy-eared. What is the genotype of each parent?
Show your work.
5. In dogs, having a short coat (L) is dominant to having a long coat (l). A breeder is looking
for a dog that has a homozygous genotype for short coat. She has four dogs with short
coats but does not know their genotypes. What could she do to know for sure what the
genotype of each dog is? FULLY EXPLAIN your answer and include Punnett squares as
part of the explanation.
Name: ________________________________ Date: ____________ Class: ______
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WS: TEST CROSS #2 – Pea Plants and Cucumbers
Name: ________________________________ Date: ____________ Class: ______
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WS: GENETICS PROBLEMS IN AGRICULTURE
(TEST CROSS #3)
Name: ________________________________ Date: ____________ Class: ______
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Monohybrid Cross Complete Dominance Practice Problems 2 - NEW
(Complete Dominance, Test Cross.)
DIRECTIONS: Please complete a Punnett square for each of the problems below that has an empty square and
show your work. Make sure you answer each part of the question that is being asked of you and that I will be able to
distinguish your capital letters from your lower-case letters!
1. In pea plants, spherical seeds (S) are dominant to dented seeds (s). In a genetic cross of two plants that are
heterozygous for the seed shape trait, what percent of the offspring should have spherical seeds?
2. A genetic cross between a pea plant heterozygous for spherical seeds and a recessive plant will yield what
percent spherical-seeded plants in the next generation? Spherical is dominant over dented.
3. A genetic cross between a heterozygous pea plant and a green-seeded plant will yield what percent greenseeded plants in the next generation? Yellow seeds are dominant to green.
4. To identify the genotype of yellow-seeded pea plants as either homozygous dominant (YY) or heterozygous
(Yy), you could do a test cross with plants of genotype ________.
Name: ________________________________ Date: ____________ Class: ______
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5. A test cross is used to determine if the genotype of a plant with the dominant phenotype is homozygous or
heterozygous. If the unknown is homozygous, all of the offspring of the test cross have the _____________
phenotype. If the unknown is heterozygous, half of the offspring will have the _____________ phenotype.
Choose from the words: dominant, incompletely dominant, recessive, complimentary, co-dominant.
6. In humans, straight toes (S) is dominant over curled toes (s). What would be the result (genotypes and
phenotypes and their percentages of the offspring) of a cross between a recessive male and a heterozygous
female?
7. In dogs, erect ears (E) is dominant over droopy ears (e). What are the results (genotypes and phenotypes
and
their percentages of the offspring) if two heterozygous dogs have a litter of
puppies?
8. Ih humans, the gene for brown eyes (B) is dominant to the gene for blue eyes (b). Two individuals
heterozygous for this characteristic marry and have children. Complete a Punnett square and show the
expected genotypes and phenotypes (and percentages of each) of the
offspring.
Name: ________________________________ Date: ____________ Class: ______
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9. In humans, the gene for right-handedness (R) is dominant to the gene for left-handedness (r). A left-handed
man marries a left-handed woman. Complete the Punnett squares below to show all of the possibilities for
their children. Don’t forget the expected genotypes and phenotypes (and percentages) of the offspring!
10. In chimpanzees, straight fingers are dominant to bent fingers. Complete a Punnett square to show the
genotypes and phenotypes expected for the following cross: A heterozygous male and a homozygous bent
female.
11. In fruit flies, straight wings is dominant over curly. Show with Punnett squares how you would determine if a
straight-winged fly were heterozygous (Ww) or homozygous (WW). Then below, explain what you did.
Name: ________________________________ Date: ____________ Class: ______
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NOTES: DIHYBRID CROSSES
•
A genetic cross that involves looking at two different traits at the same time.
•
Example: Seed color and seed shape.
•
A plant heterozygous for both seed shape and seed color would produce gametes in the
following way:
Shape:
Color:
R = round
r = wrinkled
Y = yellow
y = green
Crosses between organisms heterozygous for both traits always have a phenotypic ratio of 9:3:3:1
Name: ________________________________ Date: ____________ Class: ______
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Dihybrid Cross Poster Instructions
1.
Think of an organism you can draw…Fish? Cats? Birds? Trees? Or you can make up an organism of your
own.
Your organism: _______________________________________________
2.
Now, how can you make this drawing different? Think of two traits or characteristics involved in the
drawing…and for each, think of two forms or alleles of each trait.
The traits you choose may be real or fictional. Just be creative! You may not use shapes and colors
as your traits (i.e. blue teeth are dominant over yellow teeth) OR items that are in the form of shapes
(i.e. wings, claws, eyes, etc…)
Trait #1: ______________________________________________________
Allele A: ____________________ Allele B: ____________________
Trait #2: ______________________________________________________
Allele A: ____________________ Allele B: ____________________
3.
In this activity, you will be crossing the possible gametes of two parents who are heterozygous for two traits
and drawing the possible offspring. You must include the following:
 Dihybrid cross between two heterozygous parents – possible gametes listed on the top and side
of each cross.
 Offspring of genotypes listed and phenotypes of offspring drawn out in each box
 Listed on the right of the poster:
o The genotypes of both parents listed
o Genotypic and phenotypic ratios (not percentages!) listed at the bottom of the poster
(Chances of having offspring with each trait)
o A key (dominant and recessive traits listed and drawn out)
 COLOR IS REQUIRED- BE NEAT!
Name: ________________________________ Date: ____________ Class: ______
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RUBRIC FOR DIHYBRID CROSS POSTER
30 points total
Unacceptable
Acceptable
0-1
2
0-1
0-1
2
2
Chart set up properly – Heterozygous parents
0-1
0-1
2
2
Genotypes of each individual included in each box
Two traits with two alleles each are being changed in cross
0-1
0-1
2
2
Title includes name of species and type of Punnett square
Name is on front of poster
Chart takes up at least half of the page
____/14
Unacceptable
Poor
Average
Above
Average
TOTAL
0-1 points
2 points
3 points
4 points
Genotype key
included (dominant
trait = FF, Ff /
recessive trait = ff)
No / partial / incorrect
key
Partial key /
partially correct
key
Key complete
and mostly
correct
Key is
complete and
correct
Easy to tell the
difference between
capital and lower
case letters
Impossible to tell
capital or lower case
letters from one
another, or used
incorrect letters
Difficult to tell
capital or lower
case letters from
one another
Could have made
capital or lower
case letters more
clear
Capital or lower
case letters
very clear
Organisms do not
look at all alike or are
incomplete
Organisms look
very different
Organisms look
pretty much alike
Organisms look
very / exactly
alike
One to none of these
criteria are met
Two of these
criteria are met
Three of these
criteria are met
All four of these
criteria are met
All traits not being
changed on
organisms are
exactly the same
(color, size, type,
etc.)
Chart, writing,
drawings and overall
setup have a neat
appearance overall
___/16
TOTAL
______ / 30 POINTS = _______ %
Name: ________________________________ Date: ____________ Class: ______
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DIHYBRID CROSSES #1
***Complete these problems on a separate sheet of paper
1. In humans, nearsightedness (myopia) and the enzyme disorder PKU (phenylketonuria) are both inherited as
independently assorting autosomal recessive traits. Use N to represent the dominant allele for normal vision
and n for the recessive allele for nearsightedness. Use P to represent the dominant allele for the normal
enzyme and p for the recessive allele for phenylketonuria. A phenotypically normal man who carries
recessive alleles for both traits marries a woman who has the same genotype with regard to these traits.
a. What are the expected phenotypes and percentages (frequencies) for their progeny?
b. What is the chance that their first child will have PKU?
c. What is the chance that any child they have will be nearsighted?
d. What is the chance that their first child will be nearsighted and have PKU?
2. A daughter of the couple described above is nearsighted and heterozygous for the normal enzyme. Her
husband has the normal phenotype for both traits, although his father was nearsighted and his mother had
PKU.
a. What is the genotype of the husband?
b. What is the probability that a child of this couple is nearsighted and phenylketonuric?
c. What is the probability that a child of this couple is normal for both traits?
d. What is the probability that a child of the couple has normal vision and PKU
e. What is the probability that a child of this couple is a girl who is nearsighted and phenylketonuric?
3. 1. In the garden pea, the allele for green seed pods (Y) is dominant to the allele for yellow seed pods (y) and
the allele for full pod shape (C is dominant to the recessive allele (c) for constructed pod shape. The genes
for these two traits are carried on different pairs of chromosomes. A plant homozygous for both green seed
pods and full pod shape is crossed with a plant that has yellow seed pods and constricted pod shape.
a. Give the genotype for each parent plant
b. Indicate the kind or kinds of gametes produced by each parent
c. Give the genotypes and phenotypes of the offspring, and the percentage expected of each.
Name: ________________________________ Date: ____________ Class: ______
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4. In the jimsonweed plant, the allele for smooth seed pods, s, is recessive to the allele for spiny pods, S. At
another independently assorting locus, the allele for white flowers, w is recessive to the allele for purple
flowers, W.
a. Two plants of unknown genotype are crossed and the following progeny result: smooth and white:
27. spiny and white: 85. spiny and purple: 256. Smooth and purple: 93. Identify possible genotypes
for the parent plants.
b. In another cross, two plants of unknown genotype are crossed and produce the following progeny:
smooth and white: 75, spiny and white:82. Spiny and purple: 69; smooth and purple:77. Identify
possible genotypes for the parent plants.
Name: ________________________________ Date: ____________ Class: ______
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Practice Problems for the Complete Dominance Quiz:
Monohybrid, Test Cross and Dihybrid Problems
1. In humans, tongue rolling is a dominant trait, those with the recessive condition cannot
roll their tongues. Bob can roll his tongue, but his mother could not. He is married to
Sally, who cannot roll her tongue. What is the probability that their first born child will not
be able to roll his tongue?
2. A dog breeder has two black labs that he breeds every year. He takes careful records of
the colors of offspring produced from the breeding. Over an eight year period, he has
recorded 19 chocolate pups and 62 black pups. What are the probable genotypes of the
two parents? Show the cross(es) to prove it.
3. In guinnea pigs, short hair is dominant to long hair. Also in guinnea pigs, black eyes are
dominant to red eyes. A male guinnea pig that is heterozygous for both traits is crossed
with a female that is long haired and red eyed. What are the expected phenotypes of their
offspring and in what proportion?
Name: ________________________________ Date: ____________ Class: ______
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Use the chart below to solve the following dihybrid crosses. List the possible outcomes for the
genotypes and phenotypes of the offspring.
4. Homozygous short, homozygous colorpoint X homozygous long, homozygous normal
5. Heterozygous short, heterozygous normal X heterozygous short, heterozygous normal
Name: ________________________________ Date: ____________ Class: ______
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6. Heterozygous tabby, heterozygous normal X stripeless colorpoint
7. In tomato plants, hairy stems are produced by a dominant allele, G, and non-hairy stems
arise from the expression of its recessive counterpart allele, h. For the trait of plant
height, a dominant allele, D, produces tall plants while expression of the recessive allele,
d, produces dwarf plants. Both genes are carried on separate pairs of chromosomes. You
are given a tomato plant which has a hairy stem and is tall. Nothing is known about the
specific genotype of this plant.
c. Identify all possible genotypes for this plant
d. What procedure could be used to identify the genotype of this plant?
e. Assume that the plant in question is crossed with a plant with non-hairy stems and
dwarfed height. Two phenotypes are found in roughly equal numbers among the
316 progeny plants. Based on this information, what can be concluded about the
genetic makeup of the hairy, tall parental plant? Complete the cross below to
prove your answer.
f. Of the 316 progeny plants, roughly half were hair, tall and the rest were hairy,
dwarf. With this additional information, what can be said about the genotype of the
hairy, tall parental plant?