Genetics Quiz: Punnett Squares and More

In a cross between two heterozygous pea plants (Tt), what is the probability of obtaining a homozygous recessive offspring?

• 25%

• 50%

• 75%

• 100%

Answer explanation

In a cross of two heterozygous pea plants (Tt x Tt), the possible genotypes are TT, Tt, Tt, and tt. The homozygous recessive genotype (tt) occurs in 1 out of 4 combinations, giving a probability of 25%.

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NGSS.HS-LS3-1

In a case of incomplete dominance, if a red flower (RR) is crossed with a white flower (WW), what will be the phenotype of the offspring?

• Red

• White

• Pink

• Red and White

Answer explanation

In incomplete dominance, the traits blend. Crossing a red flower (RR) with a white flower (WW) results in offspring with a pink phenotype (RW), as neither color is completely dominant.

Which of the following is an example of codominance?

• A pink flower from red and white parents

• A red flower from red and white parents

• A flower with both red and white patches from red and white parents

• A white flower from red and white parents

Answer explanation

Codominance occurs when both alleles are expressed equally. The flower with both red and white patches shows this, as it displays traits from both red and white parents, unlike the other options which show only one color.

What is the difference between genotype and phenotype?

• Genotype is the physical appearance, phenotype is the genetic makeup(alleles)

• Genotype is the genetic makeup(alleles), phenotype is the physical appearance

• Both are the same

• Genotype is the environment, phenotype is the genetic makeup

Answer explanation

The correct choice states that genotype refers to the genetic makeup (alleles) of an organism, while phenotype describes the physical appearance resulting from that genetic makeup. They are distinct concepts in genetics.

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NGSS.HS-LS1-1

If a homozygous dominant plant (TT) is crossed with a homozygous recessive plant (tt), what will be the genotype of the offspring?

• TT

• Tt

• tt

• Tt and tt

Answer explanation

When a homozygous dominant plant (TT) is crossed with a homozygous recessive plant (tt), all offspring will inherit one dominant allele (T) and one recessive allele (t), resulting in the genotype Tt.

Tags

NGSS.HS-LS3-1

In incomplete dominance, if a black chicken (BB) is crossed with a white chicken (WW), what will be the phenotype of the offspring?

• Black

• White

• Grey

• Black and White

Answer explanation

In incomplete dominance, the traits blend. A black chicken (BB) crossed with a white chicken (WW) produces offspring with a grey phenotype (BW), as neither black nor white is fully expressed.

Tags

NGSS.HS-LS3-1

Which of the following scenarios best illustrates codominance?

• A grey rabbit from black and white parents

• A rabbit with black and white spots from black and white parents

• A black rabbit from black and white parents

• A white rabbit from black and white parents

Answer explanation

Codominance occurs when both alleles are expressed equally. A rabbit with black and white spots from black and white parents shows both colors, illustrating codominance, unlike the other options which show dominance of one color.

What is the expected phenotypic ratio of the offspring when two heterozygous individuals are crossed?

• 1dominant: 1 recessive

• 3 dominant: 1 Recessive

• 1 dominant to 2 recessive to 1 dominant

• 2dominant : 2 recessive

Answer explanation

When two heterozygous individuals (Aa x Aa) are crossed, the expected phenotypic ratio of the offspring is 3:1. This means 3 offspring will show the dominant trait for every 1 that shows the recessive trait.

Which of the following best describes a phenotype?

• The genetic makeup of an organism

• The observable characteristics of an organism

• The DNA sequence of an organism

• The environment of an organism

Answer explanation

A phenotype refers to the observable characteristics of an organism, such as physical traits and behaviors, which result from the interaction of its genotype and environment.

Which of the following must be the father's genotype?

• RR

• Rr

• rr

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2