Characteristics of Cosmids
18 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the typical range of DNA that can be contained in a cosmid?

  • 1-5 kb
  • 100-150 kb
  • 200-250 kb
  • 37-52 kb (correct)

    • What is the function of an origin of replication in a cosmid?

  • To initiate replication (correct)
  • To initiate transcription
  • To provide antibiotic resistance
  • To regulate gene expression

    • How do cosmids typically replicate in cells?

  • As a virus
  • As a phage
  • As a chromosome
  • As a plasmid (correct)

    • What is the purpose of a selectable marker in a cosmid?

    <p>To identify transformed cells</p> Signup and view all the answers

    What is the name of the sequence in a cosmid that is derived from lambda phage?

    <p>cos sequence</p> Signup and view all the answers

    What is the shape of the cosmid DNA inside the phage capsid?

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

    What is the primary function of the cosN site in cosmid DNA?

    <p>Linearizing the circular cosmid with two 'cohesive' or 'sticky ends' of 12bp</p> Signup and view all the answers

    What is the maximum size of DNA that can be carried by a cosmid?

    <p>45 kb</p> Signup and view all the answers

    What is the advantage of using cosmids in gene cloning?

    <p>They can pick up large DNA fragments, allowing for the establishment of gene libraries</p> Signup and view all the answers

    What is a limitation of using cosmids as vectors?

    <p>They cannot accept more than 50 kb of the insert</p> Signup and view all the answers

    What is the role of the cosB site in cosmid DNA?

    <p>Holding the terminase while it is cutting and separating the strands</p> Signup and view all the answers

    What is a disadvantage of using cosmids compared to plasmids?

    <p>They have slower replication</p> Signup and view all the answers

    What is the primary function of cos sites in cosmid DNA?

    <p>To enable the packaging of DNA into λ phage particles</p> Signup and view all the answers

    What is the origin of replication in cosmid DNA?

    <p>From plasmid DNA</p> Signup and view all the answers

    What is the characteristic of the two single-stranded regions at the ends of cosmid DNA?

    <p>They are complementary and form a duplex</p> Signup and view all the answers

    What is the purpose of the protein coat of bacteriophage in cosmid DNA?

    <p>To form inactive phage particles for transduction</p> Signup and view all the answers

    What is the consequence of the lack of structural and regulatory genes of lambda DNA in cosmid DNA?

    <p>No lysis and integration of cosmid DNA in the host cell</p> Signup and view all the answers

    What is the size range of DNA fragments that can be cloned using cosmids?

    <p>25 to 45 kb</p> Signup and view all the answers

    Study Notes

    Cosmid Vectors

    • A cosmid is a type of hybrid plasmid that contains a bacterial "ori" sequence and a Lambda phage cos sequence.
    • Cosmids are formed by joining the ends of a linearized plasmid DNA with the cos site of lambda DNA.
    • They are used as a cloning vector in genetic engineering and can be used to build genomic libraries.

    Characteristics of Cosmids

    • Cosmids can contain 37 to 52 kb of DNA, with a normal range of 45 kb.
    • They can replicate as plasmids if they have a suitable origin of replication (ori).
    • They frequently contain a gene for selection, such as antibiotic resistance.

    Cos Sequences

    • Cos sequences are ~200 base pairs long and essential for packaging.
    • They contain three important sites: cosN, cosB, and cosQ.

    Advantages of Cosmids

    • High transformation efficiency and capable of producing a large number of clones from a small quantity of DNA.
    • Can carry up to 45 kb of insert compared to 25 kb carried by plasmids and λ.
    • Used to establish gene libraries and help in the study of non-sense sequences in the genome of organisms.

    Disadvantages of Cosmids

    • Cannot accept more than 50 kb of the insert.
    • Packaging enzyme fails to pack recombinant cosmids into the phage head if any one of the two cos-ends is missing.
    • Packaging enzyme fails to pack the DNA into the phage head if more than one recombinant cosmid joins together to form a large DNA.
    • Slower replication.
    • Lack structural and regulatory genes of lambda DNA, hence no lysis and integration of cosmid DNA in the host cell.

    Examples of Cosmids

    • Col EI cosmid
    • pHC 79
    • pJB8
    • pWE cosmid

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    Learn about the features and properties of cosmids, a type of vector used in molecular biology. Understand their structure, function, and applications in gene cloning. Discover how cosmids are used to incorporate large DNA fragments into λ phage particles.

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser