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

Fill in the Blanks

What two letters go in the box highlighted yellow?

Fill in the Blanks

What two letters go in the box highlighted yellow?

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%