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Bacteriology > Chapter 7 > Flashcards

Chapter 7 Flashcards

1
Q

genome

A
  • is all the genetic information that defines an organism.

- consist of one or more DNA chromosomes

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2
Q

Two types of gene transfer are known

A
  1. Vertical transmission
    - from parent to child, or a cell to its progeny
  2. Horizontal transmission
    - transfer of pieces of DNA from one cell to another
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3
Q

structural gene

A
  • produces a functional RNA (“coding” DNA)
  • mRNA, which encodes a protein
  • rRNA, tRNA, small ncRNA, and a few others
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4
Q

DNA control sequence

A

regulates the expression of a structural gene

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5
Q

noncoding DNA

A
  • DNA that does not code for any genes

- bacterial DNA does not have a lot noncoding DNA

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6
Q

A gene

A

can operate independently of other genes

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7
Q

an operon

A
  • in prokaryotes, it may exist in tandem with other genes in a unit
  • often contain genes with related functions that need to be expressed together
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8
Q

Regulons

A
  • different genes or operons controlled by the same transcription factor (control protein)
  • can be on different parts of the chromosome
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9
Q

DNA Structure

A
  • Hydrogen bonding
  • polymer of nucleotides

nucleotide consists of three parts

  1. Nitrogenous base
    - Purine: adenine (A) and guanine (G)
    - Pyrimidine: cytosine (C) and thymine (T)
  2. Deoxyribose sugar
  3. Phosphate
  • connected to each other by covalent 5′-3′ phosphodiester bonds
  • phosphodiester backbone strands to come together in an antiparallel fashion
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10
Q

Histone-like proteins

A

help compact DNA in the

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11
Q

DNA-binding proteins

A

bind DNA

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12
Q

Transcription factors

A

can recognize specific DNA sequences and control gene expression

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13
Q

RNA Structure

A
  • Usually single-stranded
  • dsRNA viruses
  • Contains ribose sugar
  • Uracil replaces thymine
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14
Q

nucleoid

A
  • Bacteria pack their DNA into a series of loops or domains with proteins
  • Loops are anchored by histone-like proteins
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15
Q

DNA Supercoiling

A

-compacts DNA and helps open strands for gene expression

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16
Q

topoisomerases

A

-Enzymes that change DNA supercoiling

  • Example: DNA gyrase
  • Targeted by quinolone antibiotics
  • ciprofloxacin, used for anthrax and others
17
Q

Replication

A
  • cellular DNA is semiconservative
  • Each daughter cell receives a double helix with one parental and one newly synthesized strand
  • begins at a single origin
  • replication bubble (ssDNA) forms
  • ends at defined termination (ter) sites located opposite to the origin
  • often multiple round of replication occurring at once
18
Q

Bidirectional replication

A

-contains two replication forks that move in opposite directions around the chromosome

19
Q

major proteins involved in DNA replication

A
  • DnaA: initiator protein
  • DnaB: helicase
  • DNA primase: synthesis of RNA primer
  • DNA Pol III: major replication enzyme, has proofreading activity
  • DNA Pol I: replaces RNA primer with DNA
  • DNA gyrase: relieves DNA supercoiling
20
Q

Initiation of Replication

A

-start of DNA replication is precisely timed and linked to the ratio of DNA to new cell mass

In E. coli

  • DnaA accumulates during growth, and then triggers the initiation of replication.
  • DnaA-ATP complexes bind to short DNA repeats upstream of the origin.
  • Then, dsDNA is melted open by the helicase (DnaB)
21
Q

leading strand

A

is replicated continuously in the 5′-to-3′ direction

22
Q

lagging strand

A

-is replicated discontinuously in stages, each producing an Okazaki fragment

23
Q

Plasmids can replicate in two different ways

A
  1. Bidirectional replication
    - Starts at a single origin and occurs in two directions simultaneously
  2. Rolling-circle replication
    - Starts at a single origin and moves in only one direction
24
Q

Plasmids mechanisms to ensure their inheritance

A
  • Low-copy-number plasmids (often only one per chromosome) segregate equally to daughter cells using special proteins.
  • High-copy-number plasmids (often a dozen or more per cell) segregate randomly to daughter cells
25
Q

Genome libraries

A
  • also called clone libraries or clone pools

- contain a mix of all the genes in an organism as random cloned fragments

26
Q

Shuttle vectors

A

-plasmids that can replicate in at least two different organisms

27
Q

Basic cloning steps

A
  1. Cleavage with restriction enzyme
  2. DNA isolation
  3. Mixing and annealing vector and insert
  4. Ligation with DNA ligase and ATP
  5. Transformation into host strain
28
Q

polymerase chain reaction (PCR)

A
  • produce over a million-fold amplification of target DNA within a few hours.
  • Target specificity provided by synthetic DNA primers
    that base pair with target and prime DNA synthesis
29
Q

Whole-genome shotgun (WGS)

A
  • Genome is broken into thousands of pieces, which are all sequenced
  • Computers determines sequence overlaps to recreate entire genome sequence
30
Q

Metagenomics

A
  • is used to study microbial communities in organisms or different environments
  • Provides information for all organisms, even those that cannot be grown in the laboratory
  • Total DNA from a sample is shotgun sequenced
  • Bioinformatics is used to understand the genes that are present in the sample

Bacteriology (16 decks)

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