Genetics: Part 1 - Practice Quiz

If you cross a white flower (pp) with a purple flower (PP), the possible genotypes of the offspring are

• PP and pp

• All Pp

• All PP

• All pp

Answer explanation

Crossing a white flower (pp) with a purple flower (PP) results in all offspring having the genotype Pp. This is because each offspring inherits one allele from each parent, leading to the genotype Pp.

Each gene in an individual's genome has ____ alleles.

• 1

• 2

• 4

• 23

• 46

Answer explanation

Each gene has 2 alleles, one inherited from each parent. This diploid nature means individuals typically have two versions of each gene, making '2' the correct answer.

If T = Tall and t = not tall (short), what is the phenotypic ratio?

• 1:3

• 3:1

• 1:2:1

• 2:2

Answer explanation

In a monohybrid cross of Tt x Tt, the offspring genotypes are TT, Tt, Tt, and tt. This results in a phenotypic ratio of 3 Tall (TT, Tt, Tt) to 1 not tall (tt), giving a 3:1 ratio.

A ________________ trait masks the alternate form of the trait and is always expressed.

• recessive

• incomplete

• codominant

• dominant

Answer explanation

A dominant trait masks the alternate form, known as the recessive trait, and is always expressed in the phenotype. This is why the correct answer is 'dominant'.

The letters "A" and "a" are used to represent eye color in dragons (A=red, a=purple). Mama dragon is heterozygous for eye color and papa dragon is homozygous recessive for eye color. 
What is the genotypic ratio of the offspring? 

• 1 (100% AA)

• 1 (100% aa)

• 1:2:1 (25% AA; 50% Aa: 25% aa)

• 1:1 (50% AA; 50% Aa)

• 1:1 (50% Aa; 50% aa)

Answer explanation

Mama dragon (Aa) can pass either A or a, while papa dragon (aa) can only pass a. This results in 50% Aa (red) and 50% aa (purple) offspring, giving a genotypic ratio of 1:1 (50% Aa; 50% aa).

The letters "A" and "a" are used to represent eye color in dragons (A=red, a=purple). Mama dragon is heterozygous for eye color and papa dragon is homozygous recessive for eye color. 
What is the genotype of mama dragon? 

• Purple eyes

• Red eyes

• AA

• Aa

• aa

Answer explanation

Mama dragon is heterozygous, meaning she has one dominant allele (A) and one recessive allele (a). Therefore, her genotype is Aa, which corresponds to red eyes.

In tree frogs, green coloring is dominant. A black frog is crossed with a homozygous green frog. What percentage of the offspring are expected to be black?

• 50%

• 0%

• 75%

• 100%

• 25%

Answer explanation

In this cross, the black frog (homozygous recessive) is crossed with a homozygous green frog (dominant). All offspring will inherit a green allele, resulting in 0% black frogs.

Erminette chickens have codominant alleles for white (W) and black (B) feathers. What is the genotype and phenotype of a heterozygous chicken?

• WW; white

• BB; black

• BW; black and white

• Ww; white and black

• Bb; black and white

Answer explanation

Heterozygous chickens have one white (W) and one black (B) feather allele (BW). In codominance, both traits are expressed, resulting in a phenotype of black and white feathers.

If T = Tall and t = not tall (short), what is the genotypic ratio?

• 1:3

• 3:1

• 1:2:1

• 2:2

Answer explanation

In a monohybrid cross (Tt x Tt), the genotypic ratio is 1 TT : 2 Tt : 1 tt, which simplifies to 1:2:1. This indicates one homozygous tall, two heterozygous tall, and one homozygous short offspring.

If a true-breeding male plant with wrinkled seeds (ww) is crossed with a true-breeding female plant with round seeds (WW), what are the probable phenotypes of the offspring?

• 100% wrinkled seeds

• 100% round seeds

• 75% round seeds, 25% wrinkled seeds

• 50% round seeds, 50% wrinkled seeds

Answer explanation

The male plant (ww) has wrinkled seeds and the female plant (WW) has round seeds. All offspring (Ww) will inherit one round seed allele from the mother, resulting in 100% round seeds.