Dominant and Recessive Alleles

Description: This quiz evaluates your understanding of dominant and recessive alleles, which are fundamental concepts in genetics. Test your knowledge of how these alleles interact to determine the traits of an organism.
Number of Questions: 15
Created by:
Tags: genetics dominant alleles recessive alleles allele interactions traits
Attempted 0/15 Correct 0 Score 0

In a pea plant, the allele for purple flowers (P) is dominant over the allele for white flowers (p). If a homozygous purple-flowered plant (PP) is crossed with a homozygous white-flowered plant (pp), what will be the genotype and phenotype of the offspring?

  1. All offspring will be heterozygous (Pp) and have purple flowers.

  2. All offspring will be homozygous dominant (PP) and have purple flowers.

  3. All offspring will be homozygous recessive (pp) and have white flowers.

  4. Half of the offspring will be heterozygous (Pp) and have purple flowers, and the other half will be homozygous recessive (pp) and have white flowers.


Correct Option: A
Explanation:

Since the dominant allele (P) for purple flowers masks the expression of the recessive allele (p) for white flowers, all offspring will inherit one dominant allele (P) from the purple-flowered parent and one recessive allele (p) from the white-flowered parent, resulting in a heterozygous genotype (Pp). This genotype will express the dominant trait, which is purple flowers.

In humans, the allele for brown eyes (B) is dominant over the allele for blue eyes (b). If a heterozygous brown-eyed parent (Bb) is crossed with a homozygous blue-eyed parent (bb), what is the probability of having a blue-eyed child?

  1. 0%

  2. 25%

  3. 50%

  4. 75%


Correct Option: B
Explanation:

The heterozygous brown-eyed parent (Bb) can produce two types of gametes: B (carrying the dominant allele for brown eyes) and b (carrying the recessive allele for blue eyes). The homozygous blue-eyed parent (bb) can only produce one type of gamete: b (carrying the recessive allele for blue eyes). When these gametes combine, there is a 25% chance of inheriting two recessive alleles (bb), resulting in a blue-eyed child.

In a certain species of plant, the allele for red flowers (R) is dominant over the allele for white flowers (r). If a red-flowered plant (RR) is crossed with a white-flowered plant (rr), what will be the genotype and phenotype of the F1 generation?

  1. All offspring will be heterozygous (Rr) and have red flowers.

  2. All offspring will be homozygous dominant (RR) and have red flowers.

  3. All offspring will be homozygous recessive (rr) and have white flowers.

  4. Half of the offspring will be heterozygous (Rr) and have red flowers, and the other half will be homozygous recessive (rr) and have white flowers.


Correct Option: A
Explanation:

Since the dominant allele (R) for red flowers masks the expression of the recessive allele (r) for white flowers, all offspring will inherit one dominant allele (R) from the red-flowered parent and one recessive allele (r) from the white-flowered parent, resulting in a heterozygous genotype (Rr). This genotype will express the dominant trait, which is red flowers.

In a genetic cross, the genotype of an individual is determined by the:

  1. Alleles inherited from both parents.

  2. Alleles inherited from the mother only.

  3. Alleles inherited from the father only.

  4. Alleles inherited from the grandparents.


Correct Option: A
Explanation:

In a genetic cross, each parent contributes half of the genetic material to the offspring. Therefore, the genotype of an individual is determined by the alleles inherited from both parents.

Which of the following is an example of a dominant allele?

  1. Blue eyes

  2. Brown eyes

  3. White flowers

  4. Red flowers


Correct Option: B
Explanation:

A dominant allele is an allele that expresses its trait even when paired with a recessive allele. In the case of eye color, brown eyes are dominant over blue eyes. Therefore, brown eyes are an example of a dominant allele.

Which of the following is an example of a recessive allele?

  1. Brown eyes

  2. Blue eyes

  3. Red flowers

  4. White flowers


Correct Option: B
Explanation:

A recessive allele is an allele that only expresses its trait when paired with another identical recessive allele. In the case of eye color, blue eyes are recessive to brown eyes. Therefore, blue eyes are an example of a recessive allele.

In a genetic cross, the phenotype of an individual is determined by the:

  1. Genotype of the individual.

  2. Environment in which the individual lives.

  3. Interaction between the genotype and the environment.

  4. All of the above.


Correct Option: D
Explanation:

The phenotype of an individual is determined by the interaction between the genotype of the individual and the environment in which the individual lives. Therefore, all of the above factors contribute to the phenotype of an individual.

Which of the following is an example of a codominant allele?

  1. Brown eyes

  2. Blue eyes

  3. Red flowers

  4. White flowers


Correct Option: C
Explanation:

A codominant allele is an allele that expresses its trait even when paired with a different allele. In the case of flower color, red flowers are codominant to white flowers. Therefore, red flowers are an example of a codominant allele.

Which of the following is an example of an incomplete dominant allele?

  1. Brown eyes

  2. Blue eyes

  3. Red flowers

  4. Pink flowers


Correct Option: D
Explanation:

An incomplete dominant allele is an allele that expresses its trait partially when paired with a different allele. In the case of flower color, pink flowers are incompletely dominant to white flowers. Therefore, pink flowers are an example of an incomplete dominant allele.

Which of the following is an example of a polygenic trait?

  1. Eye color

  2. Height

  3. Skin color

  4. All of the above


Correct Option: D
Explanation:

A polygenic trait is a trait that is controlled by multiple genes. Eye color, height, and skin color are all examples of polygenic traits. Therefore, all of the above are examples of polygenic traits.

Which of the following is an example of a monogenic trait?

  1. Eye color

  2. Height

  3. Skin color

  4. Blood type


Correct Option: D
Explanation:

A monogenic trait is a trait that is controlled by a single gene. Blood type is an example of a monogenic trait. Therefore, blood type is an example of a monogenic trait.

Which of the following is an example of a sex-linked trait?

  1. Eye color

  2. Height

  3. Skin color

  4. Color blindness


Correct Option: D
Explanation:

A sex-linked trait is a trait that is carried on the X or Y chromosome. Color blindness is an example of a sex-linked trait. Therefore, color blindness is an example of a sex-linked trait.

Which of the following is an example of an autosomal trait?

  1. Eye color

  2. Height

  3. Skin color

  4. Color blindness


Correct Option: A
Explanation:

An autosomal trait is a trait that is carried on an autosome (a chromosome that is not a sex chromosome). Eye color is an example of an autosomal trait. Therefore, eye color is an example of an autosomal trait.

Which of the following is an example of a homozygous genotype?

  1. Aa

  2. Bb

  3. CC

  4. Dd


Correct Option: C
Explanation:

A homozygous genotype is a genotype that has two identical alleles for a particular gene. CC is an example of a homozygous genotype. Therefore, CC is an example of a homozygous genotype.

Which of the following is an example of a heterozygous genotype?

  1. Aa

  2. Bb

  3. CC

  4. Dd


Correct Option: A
Explanation:

A heterozygous genotype is a genotype that has two different alleles for a particular gene. Aa is an example of a heterozygous genotype. Therefore, Aa is an example of a heterozygous genotype.

- Hide questions