Genetics Chapter 4: Chromosomes and Inheritance
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Questions and Answers

What was significant about Morgan's use of Drosophila melanogaster in his experiments?

  • They produce few offspring.
  • They can be bred quickly and produce many offspring. (correct)
  • They have a long lifespan.
  • They are resistant to genetic mutations.
  • Why are certain traits, such as white eyes, only expressed in male Drosophila in Morgan's experiments?

  • Males lack the Y chromosome.
  • It is a sex-linked trait located on the X chromosome. (correct)
  • The trait is dominant.
  • It is a result of environmental factors.
  • What does recombination refer to in genetic terms?

  • Crossing over between linked genes.
  • The inheritance of all genes separately.
  • Both A and B. (correct)
  • Independent assortment of unlinked genes.
  • What is the consequence of genes located on the same chromosome?

    <p>They tend to be inherited together.</p> Signup and view all the answers

    How does crossing over affect genetic inheritance?

    <p>It allows for new combinations of traits.</p> Signup and view all the answers

    What genetic phenomenon did Morgan's results violate?

    <p>Mendelian inheritance predictions.</p> Signup and view all the answers

    Which of the following options describes a structural anomaly in chromosomes?

    <p>A portion of a chromosome is missing.</p> Signup and view all the answers

    In humans, where are most sex-linked genes typically found?

    <p>Only on the X chromosome.</p> Signup and view all the answers

    Study Notes

    Chromosomes and Inheritance

    • Early studies by Mendel identified particles of inheritance, but he did not have knowledge about chromosomes, meiosis, or DNA.
    • Morgan's work was the first to associate specific genes with specific chromosomes.
    • Morgan used the **fruit fly, Drosophila melanogaster ** for his experiments due to its short generation time and large number of offspring.
    • White-eyed mutant fly was isolated by Morgan and his experiments showed the recessive inheritance of this trait.
    • However, white eyes were only observed in male offspring of the F2 generation suggesting a link to sex chromosomes.

    Linkage and Sex-Linked Traits

    • Genes located on the same chromosome tend to be inherited together, known as linkage.
    • Sex-linked genes are located on the sex chromosomes.
    • Morgan discovered the white eye gene was linked to the X chromosome, a sex-linked gene.
    • Females can carry the recessive trait without expressing it if they are heterozygous.

    Sex Determination

    • Sex determination varies across different organisms.
    • In humans, the Y chromosome carries few genes.
    • Most sex-linked genes in humans are found on the X chromosome (X-linked).
    • Females only express recessive traits if they are homozygous.

    Examples of Sex-Linked Traits

    • Color blindness, hemophilia, and immune system defects are human sex-linked traits.

    Crossing Over and Recombination

    • Morgan's experiment with body color and wing shape showed deviations from typical Mendelian inheritance.
    • Linked genes are usually inherited together but recombination can occur.
    • Independent assortment leads to recombination of unlinked genes.
    • Crossing over allows recombination of linked genes.

    Genetic Mapping

    • Recombination frequency can be used to determine the approximate order and distance of genes on a chromosome.
    • The greater the distance between genes, the more likely a crossover will occur.

    Structural Anomalies

    • Deletions occur when a portion of a chromosome is missing.
    • Duplications arise when a portion of a chromosome is duplicated, leading to gene dosage effects.
    • Inversions involve a portion of the chromosome being flipped in orientation

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    Description

    Explore the fundamental concepts of chromosomes and inheritance as established by early geneticists like Mendel and Morgan. This quiz covers linkage, sex-linked traits, and the significant findings from Morgan's experiments with fruit flies, illuminating the understanding of genetic inheritance and chromosome behavior.

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