Basic Genetics: Epistasis Overview
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Basic Genetics: Epistasis Overview

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Questions and Answers

What phenotype is expressed when the genotype is homozygous recessive (aa)?

  • Only black code color
  • The phenotypes of both B and b (correct)
  • Only brown coat color
  • No phenotype expressed

    • What is the phenotypic ratio produced by the dominant epistasis in the example given?

  • 3:1:3
  • 12:3:1 (correct)
  • 9:3:4
  • 16:0:0

    • In the context of dogs' coat colors, which genotype would produce a black coat color?

  • iiBB
  • IiBb
  • IiBB or IiBb (correct)
  • IIBb

    • Which potential explanation was given for the inheritance of the Cream-Eye allele in Drosophila?

    <p>Mutation of the eosin allele into a cream allele</p> Signup and view all the answers

    Which combinations of alleles produce the same phenotype in the example of dominant epistasis?

    <p>A-B- and A-bb</p> Signup and view all the answers

    What is an exception to Mendel's laws related to inheritance?

    <p>All of the above</p> Signup and view all the answers

    Which of the following describes nondisjunction?

    <p>Failure of chromosomes to separate properly during cell division</p> Signup and view all the answers

    What phenomenon occurs when one gene affects multiple phenotypic traits?

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

    Which of the following is NOT a type of epistasis?

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

    In Mendelian genetics, what does epistasis often lead to?

    <p>Modified ratios in inheritance patterns</p> Signup and view all the answers

    Which of the following correctly describes the chromosomal basis of sex determination in humans?

    <p>Sex is determined by the presence of Y chromosome</p> Signup and view all the answers

    What is a common result of nondisjunction in humans?

    <p>Genetic disorders such as Down syndrome</p> Signup and view all the answers

    Which of the following best describes epistasis in genetic interactions?

    <p>The effect of one gene masking the effect of another gene</p> Signup and view all the answers

    What type of epistasis is represented by a phenotypic ratio of 12:3:1?

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

    In which type of epistasis would recessive alleles at one locus override expression of alleles at another locus?

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

    What is the phenotypic ratio associated with duplicate dominant genes?

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

    Which term describes the situation where one gene affects multiple traits?

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

    What is the phenotypic ratio indicative of duplicate recessive genes?

    <p>9:7</p> Signup and view all the answers

    Which interaction occurs when two or more different genes influence the outcome of a single trait?

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

    Which of the following ratios represents the cumulative effects of duplicate genes?

    <p>9:6:1</p> Signup and view all the answers

    What is the ratio typically associated with dominant and recessive interactions in epistasis?

    <p>13:3</p> Signup and view all the answers

    What is the phenotypic ratio resulting from a cross between RRBB and rrbb?

    <p>9:6:1</p> Signup and view all the answers

    In a cross that leads to a 15:1 ratio, what phenotype is produced by all combinations except for one?

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

    Which of the following genotypes produces a white phenotype when both alleles are recessive?

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

    What type of gene interaction occurs when identical phenotypes are produced by both homozygous recessive genotypes in a ratio of 9:7?

    <p>Duplicate recessive genes</p> Signup and view all the answers

    When two dominant alleles act independently but lead to the same phenotype, which phenotypic ratio is typically observed?

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

    In the context of gene interactions, what is meant by 'enzyme redundancy'?

    <p>Two enzymes produce the same product</p> Signup and view all the answers

    Which crossings pair will produce a purple phenotype in a 9:7 ratio?

    <p>C_P_ and C_pp</p> Signup and view all the answers

    What color is produced by the genotype RrBb?

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

    What ratio is typically produced from a dihybrid cross involving two independent loci?

    <p>9:3:3:1</p> Signup and view all the answers

    Which of the following best describes the term 'epistatic' in genetics?

    <p>An allele that can mask the expression of another allele</p> Signup and view all the answers

    What can be concluded if a genetic interaction results in a phenotypic ratio of 12:3:1?

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

    How does complementary gene action differ from epistasis?

    <p>Complementary gene action requires alleles from both loci to express a phenotype</p> Signup and view all the answers

    In the inheritance of comb morphology in chickens studied by Bateson and Punnett, which combination produces a single comb phenotype?

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

    What occurs when either locus is homozygous for a null mutation in an epistatic interaction?

    <p>None of the enzymes for the pathway will be produced</p> Signup and view all the answers

    Which of the following ratios can potentially result from epistatic alleles affecting the same trait?

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

    Which of the following statements best describes the relationship between enzymes C and P in complementary gene action?

    <p>Both enzymes must be present to produce a specific phenotype</p> Signup and view all the answers

    What flower color is produced by the genotype AAbb?

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

    In the context of duplicate recessive genes, what is the resulting genotypic ratio of AABB, AABb, AaBB, AaBb in F2?

    <p>9:7</p> Signup and view all the answers

    Which of the following combinations produces a color white flower in the context of dominant and recessive gene interaction?

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

    What phenotypic ratio corresponds to dominant epistasis?

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

    Which genotype produces a red flower according to the given epistatic interactions?

    <p>A-bb</p> Signup and view all the answers

    In the context of epistatic ratios, what is the classical ratio of A-B- genotypes?

    <p>9</p> Signup and view all the answers

    Which of the following ratios describes the outcome of duplicate dominant genes?

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

    Which pairing of parental genotypes will result in AaBb offspring that are white?

    <p>AAbb x aaBB</p> Signup and view all the answers

    What is the outcome of the genotype combination A-B- at F2 generation?

    <p>Purple flowers</p> Signup and view all the answers

    How many distinct phenotypes result from the F2 generation when crossing A- with bb?

    <p>2</p> Signup and view all the answers

    Study Notes

    Course Information

    • Course name: Basic Genetics/Genetics
    • Course codes: SSCG 2753/SSCY 2733
    • Learning objective 1 (CLO1): Identifying exceptions to Mendel's Laws, understanding chromosomal inheritance (sex determination, nondisjunction), chromosome variations, and principles of Mendel's laws with exceptions (pleiotropy and epistasis).

    Epistasis

    • Definition: The effect of one gene pair masking or modifying another gene pair's effect.
    • Six types of epistasis:
      • Dominant epistasis (12:3:1)
      • Recessive epistasis (9:3:4)
      • Duplicate genes with cumulative effect (9:6:1)
      • Duplicate dominant genes (15:1)
      • Duplicate recessive genes (9:7)
      • Dominant and recessive interaction (13:3)
    • Complementary gene action: Enzymes cooperate to produce a product, thus complementing each other.
    • Quantitative loci: Loci that control quantitatively measurable traits.
    • Pleiotropy: One gene affecting multiple traits.

    Examples of Epistasis

    • Comb morphology in chickens (9:3:3:1 ratio)
      • Four different comb morphologies: rose, pea, walnut, single
    • Coat colors of dogs (12:3:1 ratio)
      • Epistatic gene inhibits expression of coat color genes
    • Flower color of peas (9:3:4 ratio)
    • Color of wheat kernels (9:6:1 ratio)
    • Sex-linked genes and the cream-eye allele in Drosophila (12:3:1)

    Summary of ratios for the different types of Epistasis

    • Classical ratio is 9:3:3:1

    • Dominant epistasis: 12:3:1

    • Recessive epistasis: 9:3:4

    • Duplicate genes with cumulative effect: 9:6:1

    • Duplicate dominant genes: 15:1

    • Duplicate recessive genes: 9:7

    • Dominant and recessive interaction: 13:3

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    CLO1 Part 4 PDF - Basic Genetics

    Description

    This quiz focuses on the concept of epistasis and its six different types, including dominant and recessive epistasis. Additionally, it examines how gene interactions can affect phenotypic expressions and the principles of complementary gene action. Test your understanding of these key genetic concepts!

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