Sex-Linked Inheritance in Mammals
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Questions and Answers

What is the genotype of a male who expresses a sex-linked recessive trait?

  • Heterozygous Xa
  • Homozygous Xa
  • Hemizygous Xa (correct)
  • Homozygous XA
  • What is the probability that a son inherits an X-linked recessive allele from a carrier mother?

  • 25%
  • 50% (correct)
  • 100%
  • 75%
  • What is the notation for an X-linked dominant allele?

  • XxA
  • XA (correct)
  • Xa
  • XAX
  • A female who is homozygous for an X-linked dominant allele will transmit the allele to which of her offspring?

    <p>All sons and daughters</p> Signup and view all the answers

    What is the term used to describe males who have only one X chromosome in relation to sex-linked genes?

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

    A male who is affected by an X-linked recessive trait will transmit the allele to which of his offspring?

    <p>Only daughters</p> Signup and view all the answers

    What is the probability that a child will have the trait if a carrier mates with a male who has the trait?

    <p>50%</p> Signup and view all the answers

    What is the name of the gene on the human X chromosome that causes Duchenne muscular dystrophy?

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

    What is the name of the coagulation factor IX gene on the human X chromosome that causes Haemophilia B?

    <p>F9</p> Signup and view all the answers

    What is the notation for the genotype of a carrier female who has one copy of the X-linked recessive allele?

    <p>XA Xa</p> Signup and view all the answers

    What is the proportion of males affected by Haemophilia A?

    <p>1/10,000</p> Signup and view all the answers

    Why do many more males than females have sex-linked disorders?

    <p>Because males have XY chromosomes</p> Signup and view all the answers

    What is the expected phenotypic ratio if the genes controlling body colour and wing size are genetically unlinked?

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

    Why are the recombinant phenotypes underrepresented in Morgan's experiment?

    <p>Because the genes are closely physically linked</p> Signup and view all the answers

    What is the primary difference between Morgan's experiment and Mendel's dihybrid crosses in pea plants?

    <p>Genetic linkage of the genes</p> Signup and view all the answers

    What is the purpose of studying genetic linkage in Drosophila melanogaster?

    <p>To understand genetic inheritance patterns</p> Signup and view all the answers

    What increases the likelihood of recombination between linked genes?

    <p>Physical distance between the genes</p> Signup and view all the answers

    What can be inferred about the genes controlling body colour and wing size in Drosophila melanogaster?

    <p>They are located close together on the same chromosome</p> Signup and view all the answers

    What is the primary purpose of the fluorescent yellow dye in the image?

    <p>To tag a specific gene on the chromosomes</p> Signup and view all the answers

    What was the significant discovery made by Thomas Hunt Morgan in the 1900s?

    <p>The association of a specific gene with a specific chromosome</p> Signup and view all the answers

    What is the main concept that explains how genes are inherited?

    <p>The chromosomal basis of Mendel's laws</p> Signup and view all the answers

    What is the term for a segment of DNA that carries information necessary for the development of an organism?

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

    What is the term for a variation of a gene that results in a different phenotype?

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

    What is the organism that was used by Thomas Hunt Morgan to study the chromosomal basis of inheritance?

    <p>Drosophila melanogaster</p> Signup and view all the answers

    What is the genotype of the wild type Drosophila melanogaster female in the experiment?

    <p>b+ b+ vg+ vg+</p> Signup and view all the answers

    What is the phenotype of the offspring if the genes for body colour and wing size are not linked?

    <p>All offspring will have a combination of grey bodies and vestigial wings or black bodies and normal wings.</p> Signup and view all the answers

    What is the purpose of crossing the wild type female with a male that has both mutant phenotypes in the experiment?

    <p>To determine the genetic linkage between the body colour and wing size genes.</p> Signup and view all the answers

    What is the notation for the mutant allele of the body colour gene?

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

    Why are the genes for body colour and wing size not sex-linked in Drosophila melanogaster?

    <p>Because they are on an autosomal chromosome.</p> Signup and view all the answers

    What is the result of the experiment performed by Thomas Hunt Morgan and his team?

    <p>The genes for body colour and wing size are linked.</p> Signup and view all the answers

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