Punnett Square Quiz
Punnett Squares – Basic Introduction
Quiz Answers
1. Tall is dominant to short. A homozygous tall plant is crossed with a short plant. What will be the phenotypes of the offspring?
- 100% tall
- 50% tall, 50% short
- 75% tall, 25% short
- 25% tall, 75% short
2. Green is dominant to yellow. Two heterozygous green plants are crossed. What are the genotypes of the offspring?
- 100% Gg
- 50% GG, 50% Gg
- 25% GG, 50% Gg, 25% gg
- 75% Gg, 25% gg
3. Purple is dominant to white. A heterozygous purple flower is crossed with a white flower. What are the genotypes and phenotypes of the offspring?
- 100% Pp (purple)
- 50% Pp (purple); 50% pp (white)
- 75% Pp (purple); 25% pp (white)
- 25% PP, 50% Pp, 25% pp
- 75% purple, 25% white
4. In humans, brown eyes are dominant over blue eyes. What would be the allele key you would make from this information?
- B-brown b-blue
- B-blue b-brown
- BB-brown Bb-blue
- bb-brown Bb-blue
5. If brown eyes are dominant over blue eyes, what would be the parent genotypes if two heterozygous brown-eyed persons were crossed?
- BB and bb
- BB and Bb
- Bb and Bb
- bb and Bb
6. If brown eyes are dominant to blue eyes, what would be the genotype of the offspring if a homozygous brown-eyed individual is crossed with a homozygous blue-eyed?
- BB
- bb
- Bb
- BB and bb
7. G = green, g = yellow The genotype for a yellow plant is…
- GG
- Gg
- gg
- all of the choices result in yellow
8. B = brown fur b = white fur In the punnett square, what is the probability for white fur?
- 0%
- 25%
- 50%
- 75%
9. Which of the following alleles is homozygous (purebred) recessive?
- Tt
- tt
- TT
- t
10. Aa is
- homozygous (purebred)
- heterozygous (hybrid)
11. Which of the following is a phenotype?
- Aa
- red hair
- heterozygous
- DNA
12. If Spongebob is homozygous for a yellow body (yellow dominant over blue), then his genotype would be …
- Yy
- yy
- YY
- Yb
13. In the punnett square shown, what must the genotype of the missing parent be?
- BB
- Bb
- bb
- Tt
14. In the punnett square shown, what is the genotypes of the two parents?
- RW and RR
- RW and WW
- RR and WW
- RW and RR
15. T = tall an t = short TT and Tt would result in the following phenotype
- short
- tall
- both tall and short
- neither tall or short
16. An allele whose trait only shows up when no dominant allele is present.
- hidden allele
- dominant allele
- recessive allele
- present allele
17. Two brown-eyed parents (Bb) have a baby. What is the chance the baby is blue-eyed?
- 0 %
- 25%
- 50%
- 75%
Punnett Square Terms to Learn
The trait that shows outwardly in the first (F1) generation (offspring).
dominant
The one trait that did not show outwardly but is still in the genes.
recessive
Codes for a trait. Each cell has two copies.
gene
Single copy of a gene. Each gene has two alleles.
allele
An individual who has two of the same alleles for a trait. Both capital or both lower case
homozygous
An individual with two different alleles for a trait. One capital and one lower case.
heterozygous
The set of genes (alleles) a person possesses.
genotype
The physical appearance that is determined by the genes.Phenotype
phenotype
Tall is dominant (T). Short is recessive (t). What is the phenotype of “Tt”?
tall
Tall is dominant (T). Short is recessive (t). What is the phenotype of “TT”?
tall
Tall is dominant (T). Short is recessive (t). What is the phenotype of “tt”?
short
Purple flowers are dominant (P). White flowers are recessive (p). What is the phenotype of “PP”?
purple
Purple flowers are dominant (P). White flowers are recessive (p). What is the phenotype of “Pp”?
purple
Purple flowers are dominant (P). White flowers are recessive (p). What is the phenotype of “pp”?
white
Yellow is dominant (Y). Green is recessive (y). What is the genotype of a heterozygous parent?
Yy
Yellow is dominant (Y). Green is recessive (y). What is the genotype of a homozygous dominant parent?
YY
Yellow is dominant (Y). Green is recessive (y). Create a Punnet Square to answer. What is the probability of an offspring of homozygous dominant parent and a heterozygous parent being yellow.
100%
Yellow is dominant (Y). Green is recessive (y). Create a Punnet Square to answer. What is the probability of an offspring of homozygous dominant parent and a heterozygous parent being green.
0%
Yellow is dominant (Y). Green is recessive (y). What is the genotype of a homozygous recessive parent?
yy
Round eye shape is dominant (R). Oval eye shape is recessive (r).
What trait will be expressed (seen/phenotype) in a heterozygous parent?
What trait will be expressed (seen/phenotype) in a heterozygous parent?
round
Round eye shape is dominant (R). Oval eye shape is recessive (r).
What trait will be expressed (seen/phenotype) in a homozygous recessive parent?
What trait will be expressed (seen/phenotype) in a homozygous recessive parent?
oval
Round eye shape is dominant (R). Oval eye shape is recessive (r).
What trait will be expressed (seen/phenotype) in a homozygous dominant parent?
What trait will be expressed (seen/phenotype) in a homozygous dominant parent?
round
Round eye shape is dominant (R). Oval eye shape is recessive (r).
What trait will be expressed in “Rr”?
What trait will be expressed in “Rr”?
round
Round eye shape is dominant (R). Oval eye shape is recessive (r).
What trait will be expressed in “rr”?
What trait will be expressed in “rr”?
oval
Round eye shape is dominant (R). Oval eye shape is recessive (r).
What trait will be expressed in “RR”?
What trait will be expressed in “RR”?
round
Which is the dominant allele? “Tt”
T
Which is the recessive allele? “Tt”
t
Is the allele pair heterozygous, homozygous dominant, or homozygous recessive? “OO”
homozygous dominant
Is the allele pair heterozygous, homozygous dominant, or homozygous recessive? “rr”
homozygous recessive
Is the allele pair heterozygous, homozygous dominant, or homozygous recessive? “Pp”
heterozygous
Traits represented by a lowercase letter (b).
recessive
Traits represented by a CAPITAL letter (B).
dominant
Genetics
Scientific study of heredity.
Trait
A characteristic that an organism can pass on to its offspring through its genes.
Cross-fertilization
Fertilization of a plant by pollen from a different plant
Hybrid
2 different alleles
Monohybrid Cross
A cross between two individuals, concentrating on only one definable trait
Allele
An alternative form of a gene.
Homozygous
An organism that has two identical alleles for a trait
Heterozygous
An organism that has two different alleles for a trait
Dominant
Describes a trait that masks the other
Recessive
An allele for a trait that will be masked unless the organism is homozygous for this trait.
Punnett Square
A tool to predict the probability of certain traits in offspring that shows the different ways alleles can combine
Phenotype
An organism’s physical appearance, or visible traits.
Genotype
An organism’s genetic makeup, or allele combinations.
Testcross
An individual of unknown genotype is crossed with a homozygous recessive individual
Dihybrid cross
Cross between two organisms where two distinct traits are being studied.
The principals of dominance, segregation, and independent assortment were described by _________________ .
Gregor Mendel
When chromosomes do not split correctly and can result in a genetic disorder, this is a cause of ___________________
Nondisjunction
Genetic diversity is a result of
Crossing over
A cross between homozygous purple-flowered and a homozygous white-flowered pea plants results in offspring with purple flowers. This demonstrates _________________
Dominance
Genotype
The genes of a organism that for one specific trait we use 2 letters to represent the genotype
Genes in an organism
Genes in an organism
Capital Letter
Represents the dominant form of a gene
Lower Case Letter
Abbreviation for the recessive form of the gene
Phenotype
Physical appearance of a trait in an organism
Alleles
Two forms of the same gene
Alleles for a trait are located at corresponding positions on homologs chromosomes
Alleles for a trait are located at corresponding positions on homologs chromosomes
Symbol
Genotype Name
Phenotype
Genotype Name
Phenotype
RR
Homozygous (Pure Dominat)
Red Thoat
Homozygous (Pure Dominat)
Red Thoat
Symbol
Genotype Name
Phenotype
Genotype Name
Phenotype
Rr
Heterogenous (Hybrid)
Red Thoat
Heterogenous (Hybrid)
Red Thoat
Symbol
Genotype Name
Phenotype
Genotype Name
Phenotype
rr
Homozygous (Pure Recessive)
White Thoat
Homozygous (Pure Recessive)
White Thoat
Why do we use two codes for the same trait?
We use two forms of the same Capital and Lower Case Letter
What are the steps to accurately make a Punnett Square?
1. Determine genotypes of the parent organisms
2. Write down cross
3. Draw a square
4. Split the letters of the genotype for each parent and put them outside the “P” square
5. Determine the possible genotypes of the offspring by filling in the “P” square
6. Summarize the results
2. Write down cross
3. Draw a square
4. Split the letters of the genotype for each parent and put them outside the “P” square
5. Determine the possible genotypes of the offspring by filling in the “P” square
6. Summarize the results
What are the Parent Pea Plants?
P Generations
What is the Genotype for the Parent Pea Plants?
Tt x tt
What is the Phenotype for the Parent Pea Plants?
Tall x Short
What are the Offsprings?
F1 Generations
What is the Genotype for the Offsprings?
50% (2/4) = Tt
50% (2/4) = tt
50% (2/4) = tt
What is the Phenotype for the Offsprings?
50% = Tall
50% = Short
50% = Short
TT
Homozygous= Pure
Tt
Heterogenous= Hybrid
tt
Homozygous= Pure
Hair texture exists at two alleles
One curly code; One straight code
aBcdeF
ABcDef
ABcDef
Each letter on the diagram stands for a allele gene
These are a pair of homologous chromosomes
These are a pair of homologous chromosomes
Homologous Chromosomes
Same size and same genetic info
What can letters be?
Capital or Lower Case
Homozygous
Two of the same alleles in the genotype (2 big letters or 2 little letters)
Heterozygous
One allele in the genotype
Ex: Cc
Ex: Cc
Mendel’s First Law: Law of Dominance
Cross parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. Offspring that are are hybrids for a trait will have only dominant trait in the phenotype
Mendel’s Second Law: Law of Segregation
During the formation of gametes, the two alleles responsible for a trait separate from each other. After, traits are recombined at fertilization producing the genotype for the traits off the offspring
Done after F1 offspring
Done after F1 offspring
Miosis
Sex cells each separate
Mendel’s Third Law: Law of Independent Assortment
Alleles for different traits are distributed to sex cells independently off of one another
Dyhybird Cross
Parents are hybrid for two different traits
RrGg x RrGg = dealing with two different traits
RrGg x RrGg = dealing with two different traits
Law:
Parent Cross:
Offspring:
Parent Cross:
Offspring:
Dominance
TT x tt = Tall x Short
100% TT = Tall
TT x tt = Tall x Short
100% TT = Tall
Law:
Parent Cross:
Offspring:
Parent Cross:
Offspring:
Segregation
Tt x Tt = Tall x Tall
75% = Tall
25% = Short
Tt x Tt = Tall x Tall
75% = Tall
25% = Short
Law:
Parent Cross:
Offspring:
Parent Cross:
Offspring:
Independent Assortment
RrGg x RrGg
RrGg x RrGg
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