Unit 8.5 Quiz 5

What is the possible percentage of each genotype resulting from this cross?

• 100% brown eyes

• 50% blue eyes; 50% brown eyes

• 25% blue eyes; 75% brown eyes

• 25% bb; 50% Bb; 25% BB

• 50% BB; 50% bb

Answer explanation

The cross results in a 1:2:1 ratio of genotypes: 25% BB, 50% Bb, and 25% bb. Thus, the correct answer is 25% bb; 50% Bb; 25% BB, indicating the distribution of brown and blue eye genotypes.

Tags

NGSS.HS-LS3-2

NGSS.HS-LS3-1

NGSS.HS-LS3-3

What is the possible percentage of each phenotype resulting from this cross?

• 100% brown eyes

• 50% blue eyes; 50% brown eyes

• 25% blue eyes; 75% brown eyes

• 25% bb; 50% Bb; 25% BB

• 50% BB; 50% bb

Answer explanation

In a typical Mendelian cross, if brown eyes (B) are dominant over blue eyes (b), a Bb x Bb cross results in 25% BB, 50% Bb, and 25% bb. Thus, 75% will have brown eyes (BB and Bb) and 25% will have blue eyes (bb).

Tags

NGSS.HS-LS3-2

NGSS.HS-LS3-1

NGSS.HS-LS3-3

The dominant trait as seen in this Punnett square is:

• yellow peas

• green peas

• Jolly Green Giant peas.

• there is no dominant trait shown.

Answer explanation

In the Punnett square, yellow peas are typically dominant over green peas. Therefore, the presence of yellow peas indicates the dominant trait, making 'yellow peas' the correct answer.

Tags

NGSS.HS-LS3-2

NGSS.HS-LS3-1

Two brown-eyed parents are both heterozygous (Bb). What is the probability of the baby being blue eyed?

 

• 0 %

• 25 %

• 50 %

• 75 %

• 100 %

Answer explanation

Both parents are Bb, so the Punnett square shows a 25% chance (bb) for blue eyes. Thus, the probability of the baby being blue-eyed is 25%.

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-3

A pea plant has two dominant alleles for plant height – tall.  We say that this plant is:

• heterozygous dominant.

• heterozygous recessive.

• homozygous dominant.

• homozygous recessive.

Answer explanation

The pea plant has two dominant alleles for height, meaning both alleles are the same and dominant. This is defined as homozygous dominant, distinguishing it from heterozygous, which would involve different alleles.

A pea plant has two different alleles for flower color: a purple allele (which is dominant) and a white allele (which is recessive).  According to Mendelian genetics, the pea plant will have:

• white flowers.

• purple flowers.

• purple and white petals.

• pale purple flowers.

Answer explanation

The purple allele is dominant over the white allele. Therefore, any pea plant with at least one purple allele will exhibit purple flowers, making 'purple flowers' the correct answer.

Tags

NGSS.HS-LS3-2

In one box of a Punnett square, two identical capital letters indicate a gene which is:

• homozygous dominant.

• homozygous recessive.

• heterozygous dominant.

• heterozygous recessive.

Answer explanation

In a Punnett square, two identical capital letters (e.g., AA) represent a homozygous dominant genotype, indicating that both alleles are the same and dominant. Therefore, the correct answer is homozygous dominant.

The variance in a gene is called:

• a cell.

• a centromere.

• an allele.

• a nucleus.

Answer explanation

The variance in a gene refers to the different forms it can take, known as alleles. Each allele represents a variation of a gene, making 'an allele' the correct answer.

Tags

NGSS.HS-LS3-2