23 Questions
Which type of gene interaction refers to the phenomenon where the expression of one gene masks or modifies the expression of another gene?
Epistasis
What is gene-gene interaction?
It refers to the cellular function of numerous gene products contributing to a common process or pathway
What are the phenotypic ratios observed in the F2 generation in a dihybrid cross involving genes showing complementary gene action?
1:2:1
In the example given, which gene is epistatic and responsible for wing formation in Drosophila?
Wingless gene
What is the molecular basis for normal wild-type coat color in mice?
Black allele is dominant to agouti allele
Which type of gene interaction involves two genes at different loci contributing to a single phenotype without physically interacting with each other?
Supplementary/Additive genes
What term describes genes that affect multiple, apparently unrelated, phenotypes?
Pleiotropy
Which gene-gene interaction involves an interaction between two or more genes that govern a trait?
Epistasis
What is the term for a metabolic disorder in humans caused by a deficiency of the enzyme phenylalanine hydroxylase?
Phenylketonuria (PKU)
What is the term for genes that converge to result in a single phenotype, such as skin color?
Polygenic traits
What is the phenomenon called when one gene masks the phenotype of another gene at a different locus?
Dominant epistasis
In females, what is responsible for mosaicism for X-linked characters?
X inactivation (Barr body)
"Late onset diseases may show age-related penetrance." What does this statement imply about late onset diseases?
"The expression of late onset diseases may depend on age."
"Genes that affect multiple, apparently unrelated, phenotypes are called pleiotropic genes." Which disorder is presented as an example of pleiotropy?
"Phenylketonuria (PKU)"
"Pleiotropy should not be confused with gene-gene interactions like epistasis." Why should pleiotropy not be confused with gene-gene interactions like epistasis?
"Pleiotropy involves only one gene, while epistasis involves multiple genes."
In the inheritance of flower color in the given example, what is the phenotype ratio of the F2 generation?
9:3:4
Which gene is epistatic to gene B in recessive form in the inheritance of flower color?
Gene A
What type of gene interaction is demonstrated in the cross for kernel color in wheat?
Complementary gene interaction
What is the phenotypic ratio observed in the cross for kernel color in wheat?
15:1
In the example of summer squash color inheritance, which gene is epistatic to gene Y in dominant form?
Gene W
What type of gene interaction is demonstrated in the example of summer squash color inheritance?
Dominant Epistasis
What is the phenotypic ratio observed in the example of summer squash color inheritance?
12:3:1
What type of gene interaction is demonstrated in a cross between two true-breeding strains of white-flowered sweet peas?
Complementary gene interaction
Study Notes
Gene Interactions
- Epistasis is the phenomenon where the expression of one gene masks or modifies the expression of another gene.
- Gene-gene interaction refers to the phenomenon where the expression of one gene affects the expression of another gene.
Types of Gene Interactions
- Complementary gene action involves two genes at different loci contributing to a single phenotype without physically interacting with each other.
- Pleiotropy refers to genes that affect multiple, apparently unrelated, phenotypes.
- Epistatic gene interaction involves an interaction between two or more genes that govern a trait.
Examples of Gene Interactions
- In Drosophila, the gene responsible for wing formation is epistatic.
- In mice, the molecular basis for normal wild-type coat color is due to the interaction of multiple genes.
Phenotypic Ratios
- In a dihybrid cross involving genes showing complementary gene action, the phenotypic ratios observed in the F2 generation are 9:3:3:1.
- In the inheritance of flower color, the phenotypic ratio of the F2 generation is 9:3:3:1.
- In the cross for kernel color in wheat, the phenotypic ratio observed is 12:3:1.
- In the example of summer squash color inheritance, the phenotypic ratio observed is 12:3:1.
Mosaicism and Late-Onset Diseases
- In females, mosaicism for X-linked characters is responsible for the mixture of two types of cells with different genotypes.
- Late onset diseases show age-related penetrance, implying that the disease symptoms may appear later in life.
Pleiotropy
- Pleiotropy should not be confused with gene-gene interactions like epistasis, as it refers to genes that affect multiple, apparently unrelated, phenotypes.
- Phenylketonuria (PKU) is an example of pleiotropy, where a deficiency of the enzyme phenylalanine hydroxylase leads to multiple symptoms.
This quiz covers the topic of gene interactions in genetics, specifically focusing on how genes at multiple loci determine a single phenotype. It discusses how the cellular function of gene products contributes to common processes or pathways and the development of a common phenotype.
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