Chapter 3
Heredity
NAME _______________________
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Chapter 3 Vocabulary
Gregor Mendel___________________________________________
_______________________________________________________
Heredity________________________________________________
_______________________________________________________
Dominant trait____________________________________________
________________________________________________________
Recessive trait____________________________________________
________________________________________________________
Genes___________________________________________________
________________________________________________________
Alleles_________________________________________________________________
__________________________________________
Genotype______________________________________________________________
__________________________________________
Phenotype______________________________________________________________
__________________________________________
Probability______________________________________________________________
__________________________________________
Sex
Cells__________________________________________________________________
_________________________________________
Sex
Chromosomes___________________________________________________________
__________________________________________
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The father of genetics is _________________________. He lived from the year __________ to the year
_____________. As a profession, he was a _________________ in the country _________________. He
worked in the garden and studied _________ plants to show that the inheritance of traits follows particular
laws.
_______________________ – a characteristic of an organism
___________________ – the study of how traits are passed from parents to offspring
Why Mendel used pea plants:
1. __________________________________________
2. __________________________________________
3. __________________________________________
4. __________________________________________
__________________________________________– have offspring that always show the same form of the trait
__________________________________________– a process in which one plant fertilizes the egg in a flower of a
different plant
__________________________ – tiny grains containing sperm; the male plant gamete
Mendel’s experiments:
_______ generation – parental generation
_______ generation – offspring in first cross – hybrids
__________________________ – the offspring of two different true breeding plants
__________________________ – a cross between two plants that differ in only one trait
_______ generation – the offspring that result when 2 hybrid plants are crossed
Mendel’s P cross (Parental cross) involved a true breeder short and a true breeder long. Resulted in
_______________________ Mendel’s F1 cross = F1 x F1 = ________% of the offspring were long and ______% were
short.
_____________________ – the factor that controls traits
_________________ – the possibilities of a gene (e.g. A or a)
__________________________ – one allele is dominant to a recessive allele
__________________________ – the allele that masks any other allele in a heterozygous situation (A in Aa) (symbolized
by the first letter in the dominant trait’s name, always capital)
__________________________ – the allele that is masks by another allele in a heterozygous situation (a in Aa)
(symbolized by the first letter in the dominant trait’s name, always lower case)
__________________________ – having two identical alleles for a trait (AA or aa) (Mendel called this “true-breeding”)
_________________________________ ___________________ – having two dominant alleles for a trait (AA) (Mendel
called this “true breeding dominant”)
__________________________ __________________________ – having two recessive alleles for a trait (aa) (Mendel
called this “true breeding recessive”)
__________________________ – having two different alleles for a trait (Aa)
__________________________ - the visible traits of an organism (long or short)
__________________________ - the alleles that an organism carries (AA, Aa, or aa)
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__________________________ – a model used to represent crosses between organisms
Steps to doing a Punnett Square:
1. identify the gametes of the parents
2. draw a square with 4 boxes
3. put the gametes from one parent on the top of the box and the gametes from the other parent on the side of the box
4. cross multiply to find the genotypes of the children
5. write the phenotypes of each child in the boxes
6. calculate genotypic and phenotypic ratios
Try these Punnett Squares:
1. GG
(homozygous green plant) x gg (homozygous recessive yellow plant)
Phenotypic ratio:
Green = _______%
Yellow = _______%
Genotypic ratio:
GG = _______%
Gg = _______%
gg = _______%
2. Gg (heterozygous green plant) x gg (homozygous recessive yellow plant)
Phenotypic ratio:
Green = _______%
Yellow = _______%
Genotypic ratio:
GG = _______%
Gg = _______%
3. Gg
(heterozygous green plant) x Gg (heterozygous green plant)
Phenotypic ratio:
Green = _______%
Yellow = _______%
Genotypic ratio:
GG = _______%
Gg = _______%
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Practice Punnett Squares
NAME ______________________________________________________________
1. Widow’s peak is a dominant trait in humans. If a parent does not have a widow’s peak, what are the genes that the
parent has?
2. If a parent does have a widow’s peak, what are the genes that the parent might have?
3. Long eyelashes are dominant in humans. What are the genes for a person who is a hybrid for long eyelashes?
4. The ability to roll your tongue is a dominant human trait. What are the genes for a person who is a pure dominant
person?
5. Draw a Punnett square for a cross between a person who is WW and a person who is Ww for widow’s peak.
6. Draw a Punnett square for a cross between two people who are both Rr for the ability to roll their tongues.
7. In the Punnett square you drew in number 6, were the parents able to roll their tongues?
8. In the Punnett square you drew in number 6, how many of the 4 children were able to roll their tongues?
9. In the Punnett square you drew in number 6, how many of the 4 children has the same genes as their parents?
10. In the Punnett square you drew in number 6, how many of the 4 children are pure recessive?
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1. Pink hair is dominant over blue hair in smurfs. Cross a homozygous dominant hair smurf with a homozygous
recessive hair smurf.
2. Orange skin is dominant over blue skin in oranges. Cross a heterozygous skin orange with a homozygous
dominant skin orange.
3. Black hair is dominant over red hair in Labrador retrievers. Cross a homozygous dominant hair retriever with a
heterozygous hair retriever.
4. Green pods are dominant over yellow pods in string beans. Cross 2 heterozygous pod string beans.
5. Curly hair is dominant over straight hair in poodles. Cross a purebred dominant with a true breed recessive
poodle.
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Punnett Square Practice
NAME __________________________________
CLASS ___
DATE _______
Please circle your final answer.
1. A pea plant which is heterozygous for long (Long is dominant, short is recessive) is crossed with a pea plant which is
homozygous recessive. What are the genotypic and phenotypic ratios of the offspring?
2. A person who is heterozygous for widow’s peak (Widow’s peak is dominant, no peak is recessive) has children with
another heterozygote. What are the genotypic and phenotypic ratios of the offspring?
3. A guinea pig which is homozygous dominant (black is dominant, white is recessive) is crossed with another guinea pig
which is heterozygous. What are the genotypic and phenotypic ratios of the offspring?
4. A person who does not have the ability to roll his tongue (rolling is dominant, not rolling is recessive) has children with
a person who is heterozygous for tongue rolling. What are the genotypic and phenotypic ratios of the offspring? (Hint: if
you can’t roll your tongue, and rolling is dominant, what must the genotype of a non-roller be?)
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5. Two organisms, which are heterozygous for long eyelashes, have children. (Having long eyelashes is dominant, short
eyelashes is recessive). What are the genotypic and phenotypic ratio of the offspring?
6. Two pea plants are crossed. One is homozygous recessive for long (Long is dominant and short is recessive) and the
other is heterozygous. If 100 pea plant offspring are produced, how many of them will be long?
7. A person without freckles (Freckles is dominant, no freckles is recessive) has children with a person who is
homozygous dominant for freckles. How many of their children will have freckles if they have 4 children?
8. In pea plants, green pods are dominant over yellow. If yellow plant (known to be homozygous recessive) is crossed
with a green plant (could be homozygous dominant or could be heterozygous), and the offspring are all green, what was
the genotype of the green parent?
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9. A person with a widow’s peak could be homozygous dominant or could be heterozygous. If that person is crossed with
a person without a widow’s peak, and 50% of their children do not have widow’s peaks, what was the genotype of the
parent with the widow’s peak?
10. Non-red hair is dominant over red hair. A person with red hair is crossed with a person with non-red hair. All of the
offspring have non-red hair. What was the genotype of the non-red haired parent?
11. If a pea plant which is heterozygous long is crossed with another heterozygous long pea plant, and they produce 200
offspring, how many of those offspring will be short?
12. Make up your own word problem involving free and attached ear lobes (free ear lobes are dominant over attached).
Solve the word problem.
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SpongeBob Genetics Quiz
Name ____________________________
1. For each genotype below, indicate whether it is a heterozygous (He) OR homozygous (Ho).
TT _____ Pp _____ dd _____ Ff _____ Tt _____ FF _____
Which of the genotypes listed above would be considered purebred? _____________________
2. In Squidward’s family, a blue body color (B) is dominant to green (b). Determine the phenotype for each
genotype below based on this information.
BB _________________ Bb _________________ bb _________________
3. If tall eyeballs (T) are dominant to short eyeballs(t), give the genotypes that are possible for members of
Mr. Krabbs’ family.
Tall eyeballs = ___________________ Short eyeballs = ______________________
4. SpongeBob is known for his big round eyes (R), which is dominant over an oval eye shape (r). If he is
heterozygous for his round eye shape and marries a woman with oval eye shape, what type of eyes might the
kids have?
A. List the genotypes for each:
Heterozygous round eyes - _______ Oval eyes - _______
B. Complete the Punnett square to show the possibilities that would
result if SpongeBob had children with an oval-eyed woman.
C. List the possible genotypes and phenotypes for their children.
D. What are the chances of a child with a round eye shape? ____%
E. What are the chances of a child with an oval eye shape? ____%
5. Patrick recently married Patti, a cute girl he met at a local dance. He is considered a purebred for his tall
head shape (T), which is dominant over a short head (t). If Patti is a short-headed woman, what type of
heads would their children have?
A. List the genotypes for each: Patrick - ______ Patti - _______
B. Complete the Punnett square to show the possible offspring.
C. Which type of head is most likely: tall or short? Explain.
D. Would the children be considered purebreds? Explain.
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Worksheet created by T. Trimpe 2003 http://sciencespot.net/
Design a Dragon
Name__________________________________________
In this lab you and a partner will flip a penny 10 times each and record the number
of the
heads and tails combinations for each flip. A “heads” flip represents a dominant
allele (H)
and a “tails” flip represents a recessive allele (h). When you are done,
look at
the Trait Key telling you which traits are dominant and recessive for
dragons.
Then, you will draw a dragon according to the alleles that you flipped
for. For
example, if a red body color is dominant and you flip a heads and
your partner
flips tails, you will color your dragon red because the genotype would
be Hh. You
will still color it red if your partner flips a heads, because red body color is
dominant
making an HH genotype. If a green body color is recessive, you AND your
partner will have to flip
tails to have your dragon express the green body color trait to make the genotype hh. Make sure to hand in
your flip chart and the picture of your genetically designed dragon.
Flip Trial #
Genotype (HH, Hh, hh)
Example: 1
I flipped heads (H) and my partner flipped tails (h) so the genotype
would be Hh
1
2
3
4
5
6
7
8
9
11
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Trait Key:
Trait #
Dominant
Recessive
1. Body Color
Red
Green
2. Body Spots
Colored Body Spots
NO Body Spots
3. Fire Breather
Breathes Fire
Does not Breathe Fire
4. Tail Spikes
No Tail Spikes Present
Spikes Present on Tail
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5. Teeth
Pointy Teeth
Square Teeth
6. Ear Shape
Round Ears
Pointy Ears
7. Claw Length
Short Claws
Long Claws
8. Tongue Length
Long
Short
9. Wing Color
Black
Blue
10. Stomach Color
Yellow
Orange
Name ______________________________________________________________
Punnett Squares –
Crosses Involving One Trait
In a certain species of animal, black fur (B) is dominant over brown fur (b). Using the
following Punnett square, predict the genotypes and phenotypes of the offspring whose
parents are both Bb or have heterozygous black fur.
Genotypes:
B
b
_____% homozygous black fur (BB)
_____% heterozygous black fur (Bb)
B
b
_____% homozygous brown fur (bb)
Phenotypes:
_____% black fur
_____% brown fur
Now do the same when one parent is homozygous black ()BB) and the other is homozygous
brown (bb).
Genotypes:
_____% homozygous black fur (BB)
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Repeat this process again when one parent is heterozygous (Bb) black and the other is
homozygous brown (bb).
Genotypes:
_____% homozygous black fur (BB)
_____% heterozygous black fur (Bb)
_____% homozygous brown fur (bb)
Phenotypes:
_____% black fur
Section 3-1
_____% brown fur
Review and Reinforce
Mendel’s Work
Understanding Main Ideas
Study the figure. Then answer the following questions on a separate sheet of paper.
P generation
F1 Generation
F1 Generation
F2 Generation
1. What trait in pea plants is being studied in the cross above?
2. What are the two alleles of this trait?
3. Which allele is the dominant allele? Explain how you know.
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4. Which allele is the recessive allele? Explain.
5. What alleles do the F1 offspring have? Explain which allele was inherited from which
parent.
Building Vocabulary
Match each term with its definition by writing the letter of the correct definition on the line
beside the term.
_____ 6. Genetics
a. the passing of traits from parents to offspring
_____ 7. Alleles
b. an organism with two different alleles for a trait
_____ 8. Traits
c. factors that control traits
_____ 9. Recessive allele
d. physical characteristics of organisms
_____10. Genes
e. an allele whose trait always shows up in the organism
_____11. Hybrid
f. the different forms of a gene
_____12. Heredity
g. the scientific study of heredity
_____13. Dominant allele
h. an allele whose trait is masked in the presence of a
dominant allele
Incomplete Dominance Punnett Squares
Unlike simple Mendelian dominance and recessiveness, SOME traits are inherited by INCOMPLETE dominance.
In some flowers, red (RR), white (WW), and pink (RW) colors can exist. RED and WHITE are incompletely
dominant. In some animals, fur can be black (BB), white (WW), or gray (BW). Try these:
pink flowers X white flowers
Black fur x white fur
Gray fur x gray fur
Multiple Alleles Punnett Squares
Some people have proteins on the outside of their blood cells, while other people do not.
Blood type Proteins on blood cells:
A
A
B
B
AB
A and B
O
none
Genotype
AA
AO
Phenotype
A
A
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Blood type is inherited by multiple alleles. A and B are co-dominant,
which means that they are equally dominant if they are both found
in the same person. There is one recessive allele, O. A person can
have any two of those three alleles. Genotypes and phenotypes are
summarized in the table:
Try these:
blood type AO X blood type BO
BO
BB
AB
OO
blood type AA X blood type BO
B
B
B
O
blood type BB X blood type AO
1. Fur color in huskies in INCOMPLETELY DOMINANT. Cross a brown with a white husky.
B=brown
W= white
What % of the offspring are white?_____brown?_________tan?___________
2. Cross 2 tan huskies
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What percent % of the of the offspring are
brown?____________white_________tan___________
3. HARRY AND HARRIET GOT MARRIED. HARRY HAS BLOOD TYPE O AND HARRIET
HAS BLOOD TYPE AB. THEIR BABY HAS BLOOD TYPE 0 AND IT DOES NOT LOOK
LIKE EITHER ONE OF THEM. IS LITTLE MARVIN THEIRS?
Use a punnet square to prove your answer
Hospital Mix-up!
The local hospital has reported a power outage. Unfortunately, three
babies were born during this power outage and they got mixed up!
See if you can determine which baby belongs to which set of parents based on their
blood type.
The three babies that were born are:
Baby 1 – Blood type O
Baby 2 – Blood type A
Baby 3 – Blood type AB
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Mother’s blood
type
A
Father’s
blood type
O
Lucy and Ricky
Ricardo
B
A
George and Jane
Jetson
O
B
Couple
Fred and Wilma
Flintstone
Which Baby?
Punnett Square Practice
Name: ________________________________
Date: _________ Period: _______
1. Let’s say that in seals, the gene for the length of the whiskers has two alleles. The
dominant allele (W) codes long whiskers and the recessive allele (w) codes for short
whiskers.
a. What percentage of offspring would be expected to have short whiskers from the
cross of two long-whiskered seals, on that is homozygous dominant and one that
is heterozygous?
b. If one parent seal is pure long-whiskered and the other is short-whiskered, what
percent of offspring would have short whiskers?
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2. In purple people eaters, one-horn is dominant and no horns is recessive. Draw a Punnett
square showing the cross of a purple people eater that is hybrid for horns with a purple
people eater that does not have horns. Summarize the genotypes and phenotypes of
the possible offspring.
3. In dogs, there is an hereditary deafness caused by a recessive gene, “d.” A kennel owner
has a male dog that she wants to use for breeding purposes if possible. The dog can
hear, so the owner knows his genotype is either DD or Dd. If the dog’s genotype is Dd,
the owner does not wish to use him for breeding so that the deafness gene will not be
passed on. This can be tested by breeding the dog to a deaf female (dd). Draw the
Punnett squares to illustrate these two possible crosses. In each case, what
percentage/how many of the offspring would be expected to be hearing? Deaf? How
could you tell the genotype of this male dog? Also, using Punnett square(s), show how
two hearing dogs could produce deaf offspring.
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4. In humans, brown eyes (B) are dominant over blue (b). A brown eyed man marries a
blue eyed woman and they have three children, two of whom are brown eyed and one
of whom is blue eyed. Draw the Punnett square that illustrates this marriage. What is
the man’s genotype? What are the genotypes of his children?