Introduction to Punnet Squares

Monohybrid punnet squares

What does dominant mean?

• Dominant means the stronger of the two genes.

•  It will mask the effect of the other gene.

What does recesssive mean?

• Recessive means a trait that is overpowered by the dominant trait.

How are dominant and recessive traits written? 

• Dominant traits are written with a capital letter.

• Recessive traits are written with a lowercase letter.

Multiple Select

Which of these are dominant? (Click all that apply)

• H

• h

• B

• b

Multiple Select

Which of these are recessive? (click all that apply)

• B

• b

• h

• H

• a

Homozygous versus Heterozygous

What is the difference???

What does homozygous mean???

• Homozygous means that an individual has 2 genes that alike - BOTH are dominant or BOTH are recessive.

• BOTH are capital or BOTH are lower case.

What does heterozygous mean???

• Heterozygous means that an individual has different genes-one dominant and one recessive.

• One letter is capital and the other one is lower case.

• Examples: Bb, Cc. Mm, Tt, Hh

Multiple Choice

What does homozygous mean?

• It means that an individual has 2 genes that alike - BOTH are dominant or BOTH are recessive.

• It means that an individual has different genes-one dominant and one recessive.

Multiple Choice

What does heterozygous mean?

• It means that an individual has 2 genes that alike - BOTH are dominant or BOTH are recessive.

• It means that an individual has different genes-one dominant and one recessive.

How are homozygous dominant traits written?

• Homozygous dominant traits are written with 2 capital letters.

• Examples: LL, TT, JJ 

How are homozygous recessive traits written?

• Homozygous recessive traits are written with 2 lowercase letters.

• Examples: tt, rr, jj

Multiple Choice

How are heterozygous traits written?

• hh

• WW

• Gg

Multiple Choice

Which of the following is an example of a homozygous dominant trait?

• gg

• Gg

• GG

Multiple Choice

Which of the following is an example of a homozygous recessive trait?

• hh

• WW

• Gg

Multiple Choice

Which of the following is an example of a homozygous recessive trait?

• RR

• rr

• Gg

Multiple Choice

Which of the following is an example of a homozygous dominant trait?

• RR

• rr

• Gg

Understanding Punnett Squares

Fill in the squares

​

​Making Punnet Squares

Recall, mom and dad each donate ONE allele

AA (mom) x Aa (dad)

doesn't matter WHO goes where, but each allele segregates

​

​Making your punnet square

Multiple Choice

T - tall and t = short

In the Punnett square, what belongs in the missing square?

• tt

• Tt

• TT

Multiple Choice

What allele combination should go in the missing box?

• AA

• Aa

• aa

• none of these

Multiple Choice

How many boxes would say BB?

• 1

• 2

• 4

• 0

Multiple Choice

What is the probability of homozygous dominant offspring?

• 0%

• 100%

• 50%

• 25%

Multiple Choice

What is the probability of heterozygous offspring?

• 25%

• 50%

• 0%

• 100%

Multiple Choice

What is the phenotype of the offspring? (A-Brown hair; a-blond hair) 

• 50 % Brown Hair and 50% Blond Hair 

• 25 % Brown Hair and 75% Blond Hair 

• 75 % Brown Hair and 25% Blond Hair 

• 0% Brown Hair and 100% Blond Hair 

Multiple Choice

If B = brown hair and b = blonde hair, what is the probability of brown hair?

• 25%

• 50%

• 0%

• 75%

Multiple Choice

If B = brown hair and b = blonde hair, what is the probability of brown hair?

• 25%

• 50%

• 0%

• 75%

Multiple Choice

Both parents in this Punnet square

• are homozygous dominant

• are homozygous recessive

• are heterozygous

• have blue eyes

Multiple Choice

What is the dominant trait?

• yellow pea seeds

• green pea seeds

• there is no dominant seed

• Jolly green giant

Multiple Choice

Which of the following genotypes is homozygous dominant?

• A

• Aa

• AA

• aa

Multiple Choice

Which of the following genotypes is heterozygous?

• Bb

• BB

• bb

• B

Multiple Choice

Which of the following is homozygous dominant?

• Yy

• Y

• yy

• YY

Multiple Choice

Which of the following is homozygous recessive?

• Tt

• tt

• TT

• T

Multiple Choice

In pea plants, tall is dominant to short. If 2 heterozygous plants are crossed, what % of the offspring will be short?

• 0%

• 25%

• 50%

• 75%

Multiple Choice

What are the phenotype percentages of the offspring?

(A-Brown fur color; a-white fur color)

• 50 % Brown fur and 50% White fur

• 25 % Brown fur and 75% White fur

• 75 % Brown fur and 25% White fur

• 0% Brown fur and 100% White fur

Multiple Choice

In mice, black fur (B) is dominant to white fur (b). According to the Punnett square shown, the offspring in box 4 would:

• be white.

• be heterozygous.

• be gray.

• be homozygous.

Multiple Choice

In mice, black fur (B) is dominant to white fur (b). According to the Punnett square shown, how many offspring would be black?

• 0

• 1

• 2

• 3

• 4

Multiple Choice

What allele combination should go in the missing box?

• AA

• Aa

• aa

• none of these

Multiple Choice

In a certain species of plant, the color purple (P) is dominant to the color white (p).
According to the Punnett Square, what is the probability of an offspring being purple?

• 25%

• 0%

• 100%

• 50%

Multiple Choice

In the punnett square shown, what must the genotype of the missing parent be?

• BB

• Bb

• bb

• Tt

Multiple Choice

What is the probability of heterozygous offspring?

• 25%

• 50%

• 0%

• 100%