Punnett Square Practice Quiz & Answers To Learn
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 (correct answer)
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(correct answer)
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)(correct answer)
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(correct answer)
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(correct answer)
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(correct answer)
BB and bb
7. G = green, g = yellow The genotype for a yellow plant is…
GG
Gg
gg(correct answer)
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%(correct answer)
75%
9. Which of the following alleles is homozygous (purebred) recessive?
Tt
tt(correct answer)
TT
t
10. Aa is
homozygous (purebred)
heterozygous (hybrid)(correct answer)
11. Which of the following is a phenotype?
Aa
red hair(correct answer)
heterozygous
DNA
12. If Spongebob is homozygous for a yellow body (yellow dominant over blue), then his genotype would be …
Yy
yy
YY(correct answer)
Yb
13. In the punnett square shown, what must the genotype of the missing parent be?
BB
Bb(correct answer)
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(correct answer)
RW and RR
15. T = tall an t = short TT and Tt would result in the following phenotype
short
tall(correct answer)
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(correct answer)
present allele
17. Two brown-eyed parents (Bb) have a baby. What is the chance the baby is blue-eyed?
0 %
25%(correct answer)
50%
75%
The trait that shows outwardly in the first (F1) generation (offspring).
Answer: dominant
The one trait that did not show outwardly but is still in the genes.
Answer: recessive
Codes for a trait. Each cell has two copies.
Answer: gene
Single copy of a gene. Each gene has two alleles.
Answer: allele
An individual who has two of the same alleles for a trait. Both capital or both lower case
Answer: homozygous
An individual with two different alleles for a trait. One capital and one lower case.
Answer: heterozygous
The set of genes (alleles) a person possesses.
Answer: genotype
The physical appearance that is determined by the genes.Phenotype
Answer: phenotype
Tall is dominant (T). Short is recessive (t). What is the phenotype of “Tt”?
Answer: tall
Tall is dominant (T). Short is recessive (t). What is the phenotype of “TT”?
Answer: tall
Tall is dominant (T). Short is recessive (t). What is the phenotype of “tt”?
Answer: short
Purple flowers are dominant (P). White flowers are recessive (p). What is the phenotype of “PP”?
Answer: purple
Purple flowers are dominant (P). White flowers are recessive (p). What is the phenotype of “Pp”?
Answer: purple
Purple flowers are dominant (P). White flowers are recessive (p). What is the phenotype of “pp”?
Answer: white
Yellow is dominant (Y). Green is recessive (y). What is the genotype of a heterozygous parent?
Answer: Yy
Yellow is dominant (Y). Green is recessive (y). What is the genotype of a homozygous dominant parent?
Answer: 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.
Answer: 1
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.
Answer: 0
Yellow is dominant (Y). Green is recessive (y). What is the genotype of a homozygous recessive parent?
Answer: yy
Round eye shape is dominant (R). Oval eye shape is recessive (r). What trait will be expressed (seen/phenotype) in a heterozygous parent?
Answer: 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?
Answer: 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?
Answer: round
Round eye shape is dominant (R). Oval eye shape is recessive (r).What trait will be expressed in “Rr”?
Answer: round
Round eye shape is dominant (R). Oval eye shape is recessive (r).What trait will be expressed in “rr”?
Answer: oval
Round eye shape is dominant (R). Oval eye shape is recessive (r).What trait will be expressed in “RR”?
Answer: round
Which is the dominant allele? “Tt”
Answer: T
Which is the recessive allele? “Tt”
Answer: t
Is the allele pair heterozygous, homozygous dominant, or homozygous recessive? “OO”
Answer: homozygous dominant
Is the allele pair heterozygous, homozygous dominant, or homozygous recessive? “rr”
Answer: homozygous recessive
Is the allele pair heterozygous, homozygous dominant, or homozygous recessive? “Pp”
Answer: heterozygous
Traits represented by a lowercase letter (b).
Answer: recessive
Traits represented by a CAPITAL letter (B).
Answer: dominant
Genetics
Answer: Scientific study of heredity.
Trait
Answer: A characteristic that an organism can pass on to its offspring through its genes.
Cross-fertilization
Answer: Fertilization of a plant by pollen from a different plant
Hybrid
Answer: 2 different alleles
Monohybrid Cross
Answer: A cross between two individuals, concentrating on only one definable trait
Allele
Answer: An alternative form of a gene.
Homozygous
Answer: An organism that has two identical alleles for a trait
Heterozygous
Answer: An organism that has two different alleles for a trait
Dominant
Answer: Describes a trait that masks the other
Recessive
Answer: An allele for a trait that will be masked unless the organism is homozygous for this trait.
Punnett Square
Answer: A tool to predict the probability of certain traits in offspring that shows the different ways alleles
can combine
Phenotype
Answer: An organism’s physical appearance, or visible traits.
Genotype
Answer: An organism’s genetic makeup, or allele combinations.
Testcross
Answer: An individual of unknown genotype is crossed with a homozygous recessive individual
Dihybrid cross
Answer: Cross between two organisms where two distinct traits are being studied.
The principals of dominance, segregation, and independent assortment were described by _________________ .
Answer: Gregor Mendel
When chromosomes do not split correctly and can result in a genetic disorder, this is a cause of ___________________
Answer: Nondisjunction
Genetic diversity is a result of
Answer: Crossing over
A cross between homozygous purple-flowered and a homozygous white-flowered pea plants results in offspring with purple flowers. This demonstrates _________________
Answer: Dominance
Genotype
Answer: The genes of a organism that for one specific trait we use 2 letters to represent the genotype
Capital Letter
Answer: Represents the dominant form of a gene
Lower Case Letter
Answer: Abbreviation for the recessive form of the gene
Phenotype
Answer: Physical appearance of a trait in an organism
Alleles
Answer: Two forms of the same gene Alleles for a trait are located at corresponding positions on homologs chromosomes
Symbol Genotype Name Phenotype
Answer: RR Homozygous (Pure Dominat) Red Thoat
Symbol
Genotype Name
Phenotype
Answer: Rr
Heterogenous (Hybrid)
Red Thoat
Symbol
Genotype Name
Phenotype
Answer: rr
Homozygous (Pure Recessive)
Answer: White Thoat
Why do we use two codes for the same trait?
Answer: We use two forms of the same Capital and Lower Case Letter
What are the steps to accurately make a Punnett Square?
Answer: 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
What are the Parent Pea Plants?
Answer: P Generations
What is the Genotype for the Parent Pea Plants?
Answer: Tt x tt
What is the Phenotype for the Parent Pea Plants?
Answer: Tall x Short
What are the Offsprings?
Answer: F1 Generations
What is the Genotype for the Offsprings?
Answer: 50% (2/4) = Tt
50% (2/4) = tt
What is the Phenotype for the Offsprings?
Answer: 50% = Tall
50% = Short
TT
Answer: Homozygous= Pure
Tt
Answer: Heterogenous= Hybrid
tt
Answer: Homozygous= Pure
Hair texture exists at two alleles
Answer: One curly code; One straight code
aBcdeF
Answer: ABcDef
Each letter on the diagram stands for a allele gene
Answer: These are a pair of homologous chromosomes
Homologous Chromosomes
Answer: Same size and same genetic info
What can letters be?
Answer: Capital or Lower Case
Homozygous
Answer: Two of the same alleles in the genotype (2 big letters or 2 little letters)
Heterozygous
Answer: One allele in the genotype
Ex: Cc
Mendel’s First Law: Law of Dominance
Answer: 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
Answer: 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
Miosis
Answer: Sex cells each separate
Mendel’s Third Law: Law of Independent Assortment
Answer: Alleles for different traits are distributed to sex cells independently off of one another
Dyhybird Cross
Answer: Parents are hybrid for two different traits
RrGg x RrGg = dealing with two different traits
Law:
Parent Cross:
Offspring:
Answer: Dominance
TT x tt = Tall x Short
100% TT = Tall
Law:
Parent Cross:
Offspring:
Answer: Segregation
Tt x Tt = Tall x Tall
75% = Tall
25% = Short
Law:
Parent Cross:
Offspring:
Answer: Independent Assortment
RrGg x RrGg