Practice Monohybrid Crosses

A couple has three brown-eyed children. The parents are brown-eyed (Bb). The allele for brown eyes is dominant over the allele for blue eyes. They believe the fourth child they have will be blue-eyed. Which statement below explains what actually will happen?

• The couple will have a blue-eyed fourth child.

• The couple will have a brown-eyed fourth child.

• They have a 75% chance of having a blue-eyed child.

• They have a 25% chance of having a blue-eyed child.

Tags

NGSS.HS-LS3-3

What is the genotypic ratio of the offspring?

• 3 AA : 1 aa

• 1 AA : 3 aa

• 1 AA : 2 Aa : 1 aa

• 2 AA : 2 aa

Tags

NGSS.HS-LS4-3

What are the phenotype percentages of the offspring?

• 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

Tags

NGSS.HS-LS3-1

In cacti, long arms (A) are dominant to short arms (a).  Suppose 2 heterozygous cacti are crossed.  What percentage of their offspring are expected to have short arms?

• 0%

• 25%

• 75%

• 100%

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

In a monohybrid cross between two heterozygous pea plants (Tt), what is the probability of producing a pea plant with tall stems (T-)? Scarlett and Kai are experimenting in their biology class to understand how traits are passed in pea plants. (T is dominant for tall stems, t is recessive for short stems.)

• 25%

• 50%

• 75%

• 100%

Answer explanation

The probability of producing a pea plant with tall stems (T-) in a monohybrid cross between two heterozygous pea plants is 75% because there is a 3/4 chance of getting the dominant allele for tall stems (T) in the offspring.

Tags

DOK Level 2: Skill/Concept

What is the phenotypic ratio for the monohybrid cross between blue and brown eyes?

• 3:1

• 2:2

• 0:2:1

• 1:2:1

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

In Jessica's family gene pool, brown eyes are dominant, and blue eyes are recessive. Jessica is heterozygous for brown eyes and her husband is heterozygous for brown eyes. Complete the Punnett to show the possible genotypes for their baby.

e

f

g

d

c

a

b

B (top)

B (side)

BB

b (top)

Bb

b (side)

bb

Tags

112.34.c.6.F

having two of the same genes for the trait (sometimes called purebred).

• homozygous

• hetrozygous

• protein

• chromosome

Tags

NGSS.HS-LS3-1

Which of the following genotypes is a purebred?

• Bb

• Gg

• bb

• Dd

Which of the following alleles is homozygous recessive?

• Tt

• tt

• TT

• T