BIO207H5S Introductory Genetics Winter 2024 Lecture 4: Gene Interactions
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Questions and Answers

Which type of gene interaction refers to the phenomenon where the expression of one gene masks or modifies the expression of another gene?

  • Supplementary/Additive genes
  • Duplicate gene action
  • Epistasis (correct)
  • Complementary gene action
  • What is gene-gene interaction?

  • It refers to the cellular function of numerous gene products contributing to a common process or pathway (correct)
  • It involves the mutation of a specific gene pair altering the expression of other genes
  • It refers to the inheritance pattern based on a single gene governing a trait
  • It occurs when two or more genes physically interact with each other
  • What are the phenotypic ratios observed in the F2 generation in a dihybrid cross involving genes showing complementary gene action?

  • 9:3:3:1
  • 1:1:2:4
  • 1:2:1 (correct)
  • 12:3:1
  • In the example given, which gene is epistatic and responsible for wing formation in Drosophila?

    <p>Wingless gene</p> Signup and view all the answers

    What is the molecular basis for normal wild-type coat color in mice?

    <p>Black allele is dominant to agouti allele</p> Signup and view all the answers

    Which type of gene interaction involves two genes at different loci contributing to a single phenotype without physically interacting with each other?

    <p>Supplementary/Additive genes</p> Signup and view all the answers

    What term describes genes that affect multiple, apparently unrelated, phenotypes?

    <p>Pleiotropy</p> Signup and view all the answers

    Which gene-gene interaction involves an interaction between two or more genes that govern a trait?

    <p>Epistasis</p> Signup and view all the answers

    What is the term for a metabolic disorder in humans caused by a deficiency of the enzyme phenylalanine hydroxylase?

    <p>Phenylketonuria (PKU)</p> Signup and view all the answers

    What is the term for genes that converge to result in a single phenotype, such as skin color?

    <p>Polygenic traits</p> Signup and view all the answers

    What is the phenomenon called when one gene masks the phenotype of another gene at a different locus?

    <p>Dominant epistasis</p> Signup and view all the answers

    In females, what is responsible for mosaicism for X-linked characters?

    <p>X inactivation (Barr body)</p> Signup and view all the answers

    "Late onset diseases may show age-related penetrance." What does this statement imply about late onset diseases?

    <p>&quot;The expression of late onset diseases may depend on age.&quot;</p> Signup and view all the answers

    "Genes that affect multiple, apparently unrelated, phenotypes are called pleiotropic genes." Which disorder is presented as an example of pleiotropy?

    <p>&quot;Phenylketonuria (PKU)&quot;</p> Signup and view all the answers

    "Pleiotropy should not be confused with gene-gene interactions like epistasis." Why should pleiotropy not be confused with gene-gene interactions like epistasis?

    <p>&quot;Pleiotropy involves only one gene, while epistasis involves multiple genes.&quot;</p> Signup and view all the answers

    In the inheritance of flower color in the given example, what is the phenotype ratio of the F2 generation?

    <p>9:3:4</p> Signup and view all the answers

    Which gene is epistatic to gene B in recessive form in the inheritance of flower color?

    <p>Gene A</p> Signup and view all the answers

    What type of gene interaction is demonstrated in the cross for kernel color in wheat?

    <p>Complementary gene interaction</p> Signup and view all the answers

    What is the phenotypic ratio observed in the cross for kernel color in wheat?

    <p>15:1</p> Signup and view all the answers

    In the example of summer squash color inheritance, which gene is epistatic to gene Y in dominant form?

    <p>Gene W</p> Signup and view all the answers

    What type of gene interaction is demonstrated in the example of summer squash color inheritance?

    <p>Dominant Epistasis</p> Signup and view all the answers

    What is the phenotypic ratio observed in the example of summer squash color inheritance?

    <p>12:3:1</p> Signup and view all the answers

    What type of gene interaction is demonstrated in a cross between two true-breeding strains of white-flowered sweet peas?

    <p>Complementary gene interaction</p> Signup and view all the answers

    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.

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    Description

    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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