BIO222 Molecular Genetics
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Questions and Answers

What is the result of conjugation?

  • The recipient cell destroys the F factor
  • The F+ cell becomes F-
  • The recipient cell acquires an F factor (correct)
  • The recipient cell loses its F factor

    • What is the general term used to describe extra-chromosomal DNA?

  • Chromosome
  • Plasmid (correct)
  • F factor
  • Episome

    • What is the range of size of plasmids?

  • From 1,000 to 100,000 bp
  • From a few hundred to 10,000 bp
  • From a few thousand to 500,000 bp (correct)
  • From 10,000 to 1,000,000 bp

    • What is the purpose of fertility plasmids?

    <p>To allow conjugation</p> Signup and view all the answers

    What is the function of R factors?

    <p>To confer antibiotic resistance</p> Signup and view all the answers

    What is the function of degradative plasmids?

    <p>To digest unusual substances</p> Signup and view all the answers

    What is the function of Col-plasmids?

    <p>To kill other bacteria</p> Signup and view all the answers

    What is the function of Virulence plasmids?

    <p>To turn bacterium into pathogenic strains</p> Signup and view all the answers

    How many copies of plasmids can exist per cell?

    <p>Up to 100 copies per cell</p> Signup and view all the answers

    What is the importance of plasmids to bacterial survival?

    <p>Plasmids are usually not required for survival</p> Signup and view all the answers

    What is the consequence of a recipient cell acquiring an F factor?

    <p>It is converted from an F- to an F+ cell</p> Signup and view all the answers

    What is a characteristic of episomes?

    <p>They can integrate into a chromosome</p> Signup and view all the answers

    What determines the number of copies of a plasmid per cell?

    <p>The strength of the replication origin</p> Signup and view all the answers

    What is the primary function of resistance plasmids?

    <p>To confer resistance to antibiotics</p> Signup and view all the answers

    What is the significance of plasmids in bacteria?

    <p>They provide growth advantages to the bacteria</p> Signup and view all the answers

    What is the primary function of virulence plasmids?

    <p>To turn bacterium into pathogenic strains</p> Signup and view all the answers

    What is the characteristic of plasmids that allows them to replicate independently?

    <p>They have their own replication origin</p> Signup and view all the answers

    What is the relationship between plasmids and the bacterial chromosome?

    <p>Plasmids can integrate into the chromosome, but do not have to</p> Signup and view all the answers

    What is a common characteristic of plasmids found in bacteria and eukaryotic species?

    <p>They have their own replication origin</p> Signup and view all the answers

    What is the significance of conjugation in relation to plasmids?

    <p>It allows the transfer of plasmids between cells</p> Signup and view all the answers

    Study Notes

    Introduction to Molecular Genetics

    • The course BIO222 Molecular Genetics covers topics such as regulation of transcription and translation in eukaryotic and prokaryotic cells, genome structure, stability, and organization, and molecular genetics of development.

    Genetic Transfer and Mapping in Bacteria

    • Genetic transfer in bacteria involves the transfer of genetic material from one bacterium to another, enhancing genetic diversity.
    • There are three mechanisms of genetic transfer in bacteria: conjugation, transduction, and transformation.

    Conjugation

    • Conjugation involves direct physical contact between a donor and a recipient cell, with the transfer of genetic material.
    • Conjugation requires direct physical contact between the donor and recipient cells, mediated by sex pili (or F pili) made only by F+ strains.
    • The F factor, a small circular piece of DNA, carries genes required for conjugation, such as tra and trb genes.
    • The contact between donor and recipient cells initiates conjugation, leading to the formation of a conjugation bridge between the two cells.

    Mechanism of Transfer

    • The mechanism of transfer involves the following steps:
      • Relaxosome recognizes the origin of transfer (DNA sequence) and makes a cut in the DNA.
      • After cutting, most accessory proteins of the relaxosome are released.
      • One protein, relaxase, remains bound to the end of the T-DNA.
      • Exporter, a complex of 10-15 proteins coded by the F factor, pumps DNA/relaxase into the recipient cell.

    Plasmids

    • Plasmids are extra-chromosomal DNA molecules, present in many bacteria and a few eukaryotic species.
    • Plasmids can be circular or linear, ranging in size from a few thousand to 500,000 bp, and replicate independently of the bacterial chromosome.
    • Plasmids are usually not required for survival but can provide growth advantages to the bacteria.
    • There are five categories of plasmids: fertility plasmids, resistance plasmids, degradative plasmids, col-plasmids, and virulence plasmids.

    Mechanisms of Genetic Transfer in Bacteria

    • Genetic transfer in bacteria was discovered in 1946 by Joshua Lederberg and Edward Tatum
    • There are three mechanisms of genetic transfer in bacteria: transduction, transformation, and conjugation

    Transduction

    • When a bacteriophage infects a donor cell, it incorporates a fragment of bacterial chromosomal DNA into a newly made phage particle
    • The phage then transfers this fragment of DNA to a recipient cell, which incorporates the DNA into its chromosome by recombination

    Transformation

    • When a bacterial cell dies, it releases a fragment of its DNA into the environment
    • This DNA fragment is taken up by a recipient cell, which incorporates the DNA into its chromosome by recombination

    Conjugation

    • Conjugation requires direct physical contact between donor and recipient cells
    • It is the transfer of DNA from one bacterium to another following direct cell-to-cell contact
    • Many, but not all, species of bacteria can conjugate
    • Only certain strains of bacteria can act as donor cells

    F Factors

    • F factors are small circular pieces of DNA that carry genes necessary for conjugation
    • Strains containing an F factor are designated F+, while those lacking it are F-
    • Genes that play a role in the transfer of DNA are named tra or trb followed by a capital letter

    Conjugation Process

    • The first step in conjugation is the contact between donor and recipient cells, mediated by sex pili (or F pili)
    • Once contact is made, the pili shorten, and a conjugation bridge is formed between the two cells
    • The successful contact stimulates the donor cell to begin the transfer process
    • The mechanism of transfer involves relaxosome, exporter, and relaxase proteins
    • The result of conjugation is that the recipient cell has acquired an F factor, converting it from an F- to an F+ cell

    Plasmids

    • Plasmids are extra-chromosomal DNA molecules that are present in many bacteria and a few eukaryotic species
    • They can be circular or linear and range in size from a few thousand to 500,000 bp
    • Plasmids have their own replication origin and can replicate independent of the bacterial chromosome
    • They are usually not required for survival but can provide growth advantages to the bacteria
    • There are five different categories of plasmids: fertility plasmids, resistance plasmids, degradative plasmids, col-plasmids, and virulence plasmids

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    Description

    This quiz covers the basics of molecular genetics, including transcription and translation in prokaryotes and eukaryotes, genome structure, and molecular genetics of development. It also touches on mutations and disease gene identification.

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