Chapter 9. Transposons and Viruses

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  1. What are mobile genetic elements informally known as?
    Where are they found and how much of the cell's DNA sequences do they make up?
    What can they and what can't they do?
    What can they encode for?
    How is this related to viruses?
    • Jumping genes or transposons
    • In the cell, about half of the DNA sequences.
    • They can insert themselves into any DNA sequence but they lack the ability to leave the cell in which they reside.
    • The components they need for movement.
    • Viruses can insert themselves and leave the cell to infect another.
  2. Most common mobile genetic elements in bacteria or jumping genes or transposons are?
    Why are they called that?
    How do mobile genetic elements encode the components they need for movement (two methods)? Describe.
    • DNA-only transposons.
    • Because they move from one place to another as a piece of DNA as opposed to being converted into an RNA intermediate.
    • 1. Cut and paste transposition.
    •          Some DNA-only transposons move to the            target site by the element is                                excised from the genome and inserted into          a different site.
    • 2. Replicative transposition.
    •          DNA-only transposon replicate their DNA              before inserting into the new chromosomal          site, leaving the original copy intact at its            previous location.
  3. What enzyme does each mobile genetic element or transposon encode for?
    What does it do?
    How do mobile genetic elements mobe exons from one gene to another?
    • A specialized enzyme called a transposase. 
    • Mediate the transposon movement.
    • 1. Two mobile genetic elements of the same type are inserted near each other in a chromosome.
    • 2. Transposase recognizes the two ends of the two transposons.
    • 3. As a result, there is an imporperly excised transposon that carries a fragment of gene A, including one exon.
    • 4. When that imporperly exciesed transposon is attacks and inserts itself into another gene, gene B, the new gene includes the exon from gene A.
  4. How much of the human genome is made up of mobile genetic elements, transposons?

    How do transposons or mobile genetic elements move in eukaryotes? What is it called?
    What is the definition of Retrotransposon?

    What are the two types of retrotransposons?

    • Via RNA intermediate instead of DNA.
    • Retrotransposon
    • An transposon that moves via an RNA intermediate instead of DNA.

    L1 element (line-1) and Alu sequence.
  5. Define the L1 element.
    Describe the process of trasposition of the L1.
    What is reverse transcriptase?
    What is the Alu sequence?
    Is a human retrotransposon that is referred to as LINE-1, a long interspersed nuclear element that is transcribed into RNA by a host cell's RNA polymerase.

    • 1. Using RNA polymerase, the retrotrasnposon is transcribed into RNA.
    • 2. Reverse transcriptase uses the RNA as a template to make a double stranded DNA copy.
    • 3. That DNA copy can reintegrate into another site in the target DNA and do this process again.

    A weird enzyme that uses RNA as a template to make a double stranded DNA molecule encoded by the L1 element itself.

    It is a retrotransposon that does not encode for its own reverse transcriptase and thus depend on enzymes already present in the cell to help them move.
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Chapter 9. Transposons and Viruses
Chapter 9. Transposons and Viruses
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