Inheritance of Genes in Bacteria: 1

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  1. Plasmids are __. Linear descent—__—is not the only way in which bacteria obtain genes.
    mobile and can move easily between bacteria, even between members of different species

    repeated passage of the genome from parent to daughter cells
  2. Some of the genes in bacterial genomes have been acquired from other bacteria, possibly other species, by __. E.coli is used often for this. It was first isolated in 1885. It also has an uncomplicated genome.
    horizontal gene transfer
  3. There are two distinct regions within an E. Coli cell. There is a central area called the __, which takes up about __ of the volume of the cell. It is surrounded by a __. Most of the DNA in an E. Coli cell is contained in the __.


    peripheral region that is usually referred to simply as the cytoplasm

  4. The E. Coli __contains __. The E. coli nucleoid is made up of __ and __.

    DNA: __ of 4639 kb, corresponding to a contour length of 1.6 mm= __

    supercoiled DNA attached to a protein core

    DNA and protein

    single, circular molecule

    bacterial chromosome
  5. Because the DNA chromosome is big and the cell is small, it undergoes __, which occurs when additional turns are introduced into the DNA double helix (__) or if turns are removed (__)

    positive supercoiling

    negative supercoiling
  6. With a linear molecule, the __ introduced by over-or-underwinding is immediately released by __, but a __, having no ends, cannot reduce the strain in this way.

    Instead, the circular molecule responds by __. Supercoiling is an ideal way of __
    • torsional stress
    • rotation of the ends of the DNA molecule
    • circular molecule
    • winding around itself to form a more compact structure
    • packaging a circular molecule into a small space
  7. Supercoiling is generated and controlled by two enzymes, __ and __.

    Supercoiling must not hinder __ and __. It must also be possible to __= DNA must be folded up in a very ordered manner.
    • DNA gyrase and DNA topoisomerase I
    • accessibility and transcription

    replicate the DNA and separate the daughter molecules without everything getting tangled up
  8. Belief: __
    DNA is attached to a protein core from which supercoiled loops, each containing 10 to 100 kb of DNA, radiate out into the cell
  9. The protein component of the nucleoid includes __ and __, the two enzymes that are primarily responsible for maintaining the __, as well as a set of at least four proteins believed to have a more specific role in packaging the bacterial DNA
    DNA gyrase and DNA topoisomerase I

    supercoiled state
  10. The most abundant of these packaging proteins is __, which forms a tetramer around which approximately 60 bp of DNA becomes wound.
  11. Plasmids are __

    The cytoplasm of an E. coli cell might contain other DNA molecules called __, which are __—though some can be __.
    independent DNA molecules within a bacterial cell



  12. What do plasmids carry?
    Plasmids carry one or more genes, and often tehse genes are responsible for a useful characteristic
  13. All plasmids possess at least one DNA sequence that can act as an __, allowing tehm to __

    The smaller plasmids make use of the cell’s __ to make copies of themselves, whereas some of the larger ones carry genes that code for special enzymes that are specific for __.
    • origin of replication
    • multiply in the cell independently of the bacterial chromosome
    • own DNA replicative enzymes
    • plasmid replication
  14. A few types of plasmid are also able to replicate by doing what? 

    These __ may be stably maintained in this form through numerous cell divisions, but always at some stage exist as independent elements
    inserting themselves into the chromosome

    integrative plasmids or episomes
  15. Plasmids can be classified according to the genes they carry

    Virtually all species of bacteria harbor plasmids. Some plasmids are __to just a few related species and are found in no other bacteria, but others have a __and can exist in numerous species though they have preferences.

    broad host range
  16. Plasmids are most classified according to __. There are five main types of plasmids. 

    What are they?
    the genes that they carry and the characteristics that those genes confer on the host bacterium

    • Fertility F plasmids
    • Resistance plasmids
    • Col plasmids
    • Degradative plasmids
    • Virulence plasmids
  17. Most common type: Resistance (R) plasmids.
    they carry genes conferring on the host bacterium resistance to one or more antibacterial agents. Important in clinical microbiology
  18. Some species have copies of a second type of plasmid called a fertility or F plasmid: they do what? 
    direct conjugation between different bacteria of the same, or related, species
  19. Conjugation is a process that __

    Conjugation is one of the processes that can lead to __
    enabels two bacteria to join together so that plasmids, and possibly parts of the chromosome, can be passed from one cell to another

    horizontal gene transfer
  20. Some plasmids carry genes that __. Bacteria carrying these plasmids __. Plasmids of this type are not common in bacterial species as a whole, but are present in some strains of E. coli. They are: __
    code for toxic proteins which kill other bacteria

    gain an advantage in the competition for scarce resources

    • Col plasmids
    • Degradative plasmids
    • Virulence plasmids
  21. Col plasmids

    Degradative Plasmids

    Virulence Plasmids
    Col plasmids: codes for toxins alled colicins

    Degradative plasmids: allow the host bacterium to metabolize unusual molecules such as toluene and salicylic acid

    Virulence plasmids confer pathogenicity on the host bacterium
  22. A single bacterium can have __

    Each type of plasmid has its own __, this being the __

    Some plasmids are __and have a __ of perhaps just one or two per cell
    multiple copies of the same or different plasmids

    characteristic copy number

    number of copies of the plasmid that are present in a single bacterial cell


    low copy number
  23. Others, called __, are present in multiple copies of 50 or more

    There can also be more than one type of plasmid in a single cell but they must be __.

    If they are incompatible, then __
    • relaxed plasmids
    • compatible
    • one or the other will be lost from the cell
  24. Different types of plasmids can therefore be assigned to __ on the basis of whether or not they can __

    Plasmids from a single incompatibility group are often related to one another in various ways
    different incompatibility groups

  25. The factors determining the copy number and compatibility relationships between plasmids can be somewhat attributed to __. There are two theories for this. What is the first?
    events during replication

    • Theory 1: copy number is determined by an inhibitor molecule that prevents further replication of the plasmid once the characteristic value is reached
    • -->Replication may even be controlled by the same inhibitor molecule
  26. What is theory two?
    Theory 2: plasmid replication requires attachment to a specific binding site on the cell membrane and that incompatible plasmids compete for the same attachment sites
  27. How Daughter cells acquire Copies of the bacterial chromosome and plasmids is not well understood

    Unlike chromosomes, inheritance of plasmids is not such an absolute requirement. However, they usually __, revealing the fact that there is a mechanism
    become evenly distributed between the daughters
  28. What we know suggests that the __ plays an important role; and, the arrangement is not random.

    In different cells, the equivalent parts of the DNA molecule are always located at __.The origin of replication is always __, with the __diametrically opposite, adjacent to the wall on the other side of the cell
    arrangement of the chromosome within the nucleoid

    equivalent positions

    adjacent to the cell wall

    replication termination region
  29. When the chromosome begins to replicate, the origins of replication of the two daughter DNA molecules do what?
    move apart from one another, each toward a different end of the cell.
  30. How this occurs is unknown. But, a __ is required—passive role as it provides a framework along which the origins travel.

    One theory for this is that the origins are __
    cytoskeletal protein called MreB

    pushed apart by RNA polymerase enzymes as these gain access to the newly replicated strands in order to transcribe the genes close to the origin
  31. Outcome: __ 

    The replicated DNA molecules therefore take up the __ needed for them to become enclosed within the daughter cells that are formed when __.
    two daughter chromosomes move toward either end of the bacterium as the parent molecule is being replicated.

    appropriate positions

    cytokinesis divides the bacterium into two
  32. In a rich growth medium, one in which the bacteria are able to divide every 20 minutes or so, what happens? 

    The last parts of the replicated DNA molecules are __
    the septum begins to form across the middle of the parent cell before chromosome replication has been completed

    “pumped” across the septum by special translocase enzymes
  33. Plasmid partitioning: three mechanisms, each using a different plasmid

    Type 1 system:__
    two members of a pair of daughter plasmids are pushed apart from one another by growth of a microfilament made up of ParM proteins, which attach to each plasmid at a special sequence called parC, which is the binding site for another protein, ParR.
  34. What does ParR do?
    The latter forms a platform for attachment of the first of the ParM proteins in the growing microfilament
  35. What does parC do?
    parC is sometimes called the plasmid centromere (no similarity to eukaryotic centromere other than it being the attachment site for a microfilament)
  36. What does the parM do?
    the ParM filament grows along the axis fo the bacterium, so the replicated plasmids become pushed to opposite ends.
  37. The other systems work in similar ways, the main distinction being in __
    the identity of the protein that forms the filament that pushes the daughter plasmids to the poles
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Inheritance of Genes in Bacteria: 1
2015-11-11 03:49:57
Test Three: Zuzga
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