Genetics: Codominance and Multiple Alleles

Questions and Answers

What is the outcome when a white chicken is crossed with a black chicken under codominance?

The offspring have black feathers only.

The offspring have white feathers only.

The offspring have gray feathers.

The offspring have both black and white feathers. (correct)

Which of the following best describes multiple alleles?

More than two variations of alleles are possible. (correct)

Alleles always result in a dominant phenotype.

Only two alleles are present for a trait.

The presence of only identical alleles.

What is epistasis?

An interaction between two or more genes affecting phenotype expression. (correct)

The dominance of a single gene over multiple genes.

The phenomenon of traits blending together.

A condition where all alleles are recessive.

In masking epistasis, what is the term used for the gene that causes another gene's expression to be masked?

Epistatic gene Signup and view all the answers

What genotype in labrador retrievers results in a yellow coat due to epistasis?

ee Signup and view all the answers

What antigen is present on the red blood cells of type B blood?

B Signup and view all the answers

Which genotype corresponds to the Himalayan phenotype in rabbits?

chch Signup and view all the answers

In the context of epistasis, what does the term hypostatic refer to?

A gene that is masked by another gene Signup and view all the answers

What type of epistasis occurs when one gene completely masks the expression of another gene?

Masking epistasis Signup and view all the answers

For a Labrador retriever to have chocolate brown fur, which alleles must be present?

eeBB or eeBb Signup and view all the answers

Which rabbit genotype indicates the presence of the agouti phenotype?

Cch Signup and view all the answers

What type of blood type has no antigens on the red blood cells?

Type O Signup and view all the answers

Which of the following coat colors in Labrador retrievers indicates the presence of dark pigment?

Black Signup and view all the answers

What is codominance?

Both alleles are equally strong and visible in the phenotype. Signup and view all the answers

Which statement describes multiple alleles?

More than two alleles can exist for a single gene. Signup and view all the answers

How does an antibody function in the immune system?

It detects and destroys foreign substances in the blood. Signup and view all the answers

What role do modifier genes play in epistasis?

They can be either epistatic or hypostatic. Signup and view all the answers

In masking epistasis, how does one allele affect another?

It masks the phenotype expression of the second allele. Signup and view all the answers

What phenotype will a labrador retriever with the genotype eeBB have?

Yellow fur because of the masking effect of the e allele. Signup and view all the answers

What defines human blood type variations?

Different types of antigens present on red blood cells. Signup and view all the answers

Which of the following is an example of epistasis?

A gene affecting coat color in labradors based on the presence of another allele. Signup and view all the answers

Study Notes

Codominance

Codominance occurs when two alleles are equally expressed in a hybrid genotype.
Example: Crossing a white chicken with a black chicken results in a chicken with both black and white feathers, not gray.

Multiple Alleles

Multiple alleles refer to more than two variations of a gene in a population.
Example: Human ABO blood types have four types based on antigens present on red blood cells (A, B, AB, O).
Antigens trigger antibody production, leading to immune responses against foreign substances.

ABO Blood Types

Blood type A: A antigens, produces antibodies against B.
Blood type B: B antigens, produces antibodies against A.
Blood type AB: A and B antigens, does not produce antibodies against A or B.
Blood type O: No antigens, produces antibodies against both A and B.

Epistasis

Epistasis involves interactions between two or more genes affecting a single phenotype.
Modifier genes can either mask or modify the expression of another gene.
Two types of epistasis exist:
- Masking epistasis: One gene masks the expression of another.
- Modifying epistasis: One gene alters the expression of another gene.

Example of Masking Epistasis

Labrador retriever coat color is influenced by two alleles for pigmentation (B for dark, b for yellow).
Genotype combinations (eeBB, eeBb) will result in a yellow coat due to masking by the e allele.
Phenotypes can range from yellow to black, depending on alleles present.

Rabbit Coat Color Inheritance

Coat color in rabbits is determined by multiple alleles in a hierarchical dominance order:
- Dominant: Agouti (C) > Chinchilla (cch) > Himalayan (ch) > Albino (c).
Phenotypes and their corresponding genotypes:
- Agouti (black): CC, Ccch, Cch, Cc
- Chinchilla: cchcch, cchch, cchc
- Himalayan: chch, chc
- Albino: cc

Key Terms

Antigen: A foreign substance that triggers antibody production.
Antibody: A protein produced by the immune system that targets foreign substances.
Epistatic gene: The gene that masks or modifies expression.
Hypostatic gene: The gene being masked or modified.

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Description

Explore the fascinating concepts of codominance and multiple alleles in genetics. Understand how these forms of inheritance work and see real-life examples such as chicken feather colors and human blood types. Test your knowledge with this quiz!