Genetics STAAR Review

Which of the following is homozygous dominant?

• Mm

• MM
• mm

Tags

NGSS.HS-LS3-1

Achondroplasia is an inherited condition that affects the formation of bone in humans. The allele for achondroplasia (A) is dominant to the unaffected allele (a).

If a person who is homozygous dominant has children with a person who is homozygous recessive, what percentage of their children will likely have achondroplasia?

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-3

In domesticated dogs, hair type is controlled by two different alleles. The allele for wire hair is (H) and the allele for smooth hair is (h).

When two heterozygous dogs are crossed, what percentage of the offspring is expected to be homozygous for smooth hair?

• 0%

• 25%

• 50%

• 75%

Tags

NGSS.HS-LS3-3

What is the phenotype probability of the offspring?

(A = Brown hair; a = blonde hair) 

• 50 % Brown Hair and 50% Blonde Hair 

• 25 % Brown Hair and 75% Blonde Hair 

• 75 % Brown Hair and 25% Blonde Hair 

• 0% Brown Hair and 100% Blonde Hair 

Tags

NGSS.HS-LS3-3

The cross between two individuals with the genotype SsRr is shown in the Punnett square.

How many out of 16 offspring would be expected to be homozygous recessive for both traits?

Tags

NGSS.HS-LS3-3

Chickens can have different types of feathers. Frizzled feathers curl toward a chicken’s head.

The allele for frizzled feathers is dominant over the allele for straight feathers. In a cross between two chickens with straight feathers, what percentage of the offspring can be expected to have frizzled feathers?

• 0%

• 25%

• 50%

• 75%

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-3

In cattle the allele for cloven hooves (H) is dominant over the allele for mule-foot hooves (h). The phenotype for each trait is shown in this picture.

What is the probability of cloven hooves in the offspring of parents that are heterozygous for the trait?

• 25%

• 50%

• 75%

• 100%

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-3

In Holstein cattle the allele for black hair color (B) is dominant over the allele for red hair color (b), and the allele for polled (P), or lacking horns, is dominant over the allele for having horns (p).

What is the expected phenotypic ratio of the offspring of a BbPp × BbPp cross if these alleles sort independently?

• 16 black/polled :

  0 black/horned :

  0 red/polled :

  0 red/horned

• 12 black/polled :

  0 black/horned :

  0 red/polled :

  4 red/horned

• 4 black/polled :

  4 black/horned :

  4 red/polled :

  4 red/horned

• 9 black/polled :

  3 black/horned :

  3 red/polled :

  1 red/horned

Tags

NGSS.HS-LS3-3

In humans blood type is determined by the A, B, and O alleles. The A and B alleles are codominant to each other and dominant over the O allele. An individual with the AO genotype and an individual with the BO genotype can produce offspring with which of the following phenotypes?

• O only

• A or B only

• A, B, or O only

• A, B, AB, or O

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

What is the probability of having heterozygous offspring?

• 25%
• 50%
• 0%
• 100%

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-3