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X-Inactivation quiz #1

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  • How does a calico cat obtain its unique coat pattern?
    A calico cat's unique coat pattern results from random X-inactivation in female cats, where different X chromosomes (carrying different fur color alleles) are inactivated in different cells, leading to patches of color.
  • Which X chromosome is inactivated in a female mammal?
    In female mammals, X-inactivation is random; either the maternal or paternal X chromosome can be inactivated in each cell.
  • Which of these sequences plays a critical role in Barr body formation?
    The XIST gene sequence plays a critical role in Barr body formation by producing RNA that coats and inactivates the X chromosome.
  • Which statement best describes how X chromosomes are inactivated in female mammals?
    X-inactivation in female mammals occurs randomly in each cell, with one X chromosome becoming inactive and forming a Barr body to achieve dosage compensation.
  • Which of the following statements best applies to the inactive X chromosome in mammalian females?
    The inactive X chromosome in mammalian females becomes a Barr body, is tightly packed into heterochromatin, and is not transcribed.
  • What are the odds that a grandmother will donate her mitochondrial DNA to a future grandson?
    A grandmother will always donate her mitochondrial DNA to all her grandchildren, including grandsons, because mitochondrial DNA is inherited maternally.
  • What is the result of the activation of the XIST gene in mammals?
    Activation of the XIST gene leads to the production of RNA that coats the X chromosome, resulting in its inactivation and formation of a Barr body.
  • Where is heterochromatin not commonly located?
    Heterochromatin is not commonly located in regions of actively transcribed genes, such as euchromatin.
  • All female mammals have one active X chromosome per cell instead of two. What causes this?
    This is caused by X-inactivation, a process that randomly inactivates one X chromosome in each cell to ensure dosage compensation.
  • Which of the following best describes the function of the XIST gene in X chromosome inactivation?
    The XIST gene produces RNA that coats the X chromosome, leading to its inactivation and preventing gene expression.
  • Which of the following events results in X-inactivation in female mammals?
    Expression of the XIST gene and subsequent coating of the X chromosome with XIST RNA results in X-inactivation in female mammals.
  • In eukaryotic cells, which processes are prevented by heterochromatin formation?
    Heterochromatin formation prevents transcription and gene expression in eukaryotic cells.
  • If two X chromosomes are present in a mammalian cell, one of them is converted to a(n) ______.
    If two X chromosomes are present in a mammalian cell, one of them is converted to a Barr body.