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Microbiology > Chapter 7: microbial genetics > Flashcards

Chapter 7: microbial genetics Flashcards

1
Q

Genome

A

-the entire genetic complement of an organism , includes its genes and nucleotide sequences

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2
Q

Chromosome

A

-DNA wrapped around proteins, takes up little space in the cell

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3
Q

Haploids

A

-one copy of chromosomes

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4
Q

diploid

A
  • two copies of chromosomes
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5
Q

Prokaryotic

A
  1. usually 1 circular chromosome therefore haploid
  2. chromosomes in nucleoid region
  3. often they also contain plasmids
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6
Q

Eukaryotic

A
  1. multiple linear chromosomes usually diploid but some haploid or polyploid
  2. nuclear and some extranuclear chromosomes (mitochondria)
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7
Q

What are chromosomes made of in both eukaryotic and prokaryotic organisms?

A

-DNA and proteins

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8
Q

Plasmids

A

-are small circular DNA molecules which replicate independently from the nucleoid and often code for one or more additional cellular traits
-are not essential for normal growth, metabolism, or reproduction but can offer additional survival advantages
-some fungi and protozoa can carry plasmids
-help bacteria survive a very specific situation but not needed to live

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9
Q

Types of plasmids

A
  1. Fertility factors (F+/F-) (conjugation ability-gene that makes sex pili)
  2. Resistance factors (R+/R-) (resistance to antibiotics)
  3. Bacteriocin factors (B+/B-) (protein that kills other bacteria) (toxin production)
    4.Virulence plasmids (V+/V-) (pathogenicity- ability to infect)
  4. cryptic plasmids (no one knows their function)
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10
Q

RNA

A

-single stranded
-does not have thymine but uracil
- AU go together and GC
-sugar is ribose

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11
Q

DNA

A

-double stranded
-contains adenine, guanine, cytosine, and thymine
- AT go together and GC
-sugar is deoxyribose

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12
Q

DNA replication

A

-is an anabolic process, therefore it requires both monomers and energy
-triphosphate deoxyribonucleotides serve both functions
-has antiparallel strands that are synthesized differently

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13
Q

What is the key to replication of the bases?

A

complementarity

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14
Q

Is replication semiconservative or conservative?

A

semiconservative

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15
Q

Semiconservative

A

-the replicated DNA is part old and part new strand of the double helix. Has old parent strand and newly made strand

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16
Q

Leading strand is synthesized how?

A

continuously

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17
Q

Lagging strand is synthesized how?

A

discontinuously

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18
Q

Which direction can polymerases add nucleotides?

A

-only 5’ to 3’ to the free 3’ OH group on a carbon

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19
Q

Initial steps in DNA replication

A
  1. Helicase unwinds the double helix
  2. stabilizing proteins or SSBP (single stranded binding proteins) stabilize the replication fork (keeps it from snapping back)
    3.DNA polymerase III begins syntheses at the 3’ OH site of primers and proofreads/repairs as it adds bases (only add on 1 side)
  3. DNA polymerase I then removes primers, replaces the primers with DNA
  4. Ligase completes the backbone
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20
Q

Primase

A

-produces short RNA primers
-act as a seat for DNA polymerase III

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21
Q

Topoisomerase

A

-helps to relieve tension that comes from unwinding by helicase of DNA

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22
Q

Name the 5 enzymes involved in DNA replication

A
  1. DNA polymerase III
  2. DNA polymerase I
  3. Topoisomerase
  4. Primase
  5. Ligase
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23
Q

What are stabilizing proteins (SSBP)

A

-these are stabilizing proteins and they help stabilize the replication fork (keep it from snapping back)

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24
Q

antiparallel strand orientation

A

-the strands of DNA double helix are antiparallel because they have the same chemical structure but opposite directions
- one strand 5’ to 3’ and the other strand is 3’ to 5’

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25
Q

What forms because of the lagging strand discontinuous nature

A

-okazaki fragments

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26
Q

promoter

A

-tells the cell where the gene starts

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27
Q

terminator

A

-tells the gene where the cell ends

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28
Q

genotype

A

DNA sequence

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29
Q

phenotype

A

Physical characteristics

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30
Q

Transcription

A

Turning DNA into RNA

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31
Q

translation

A

Turning RNA to protein

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32
Q

Central dogma

A

DNA —-> RNA —> Protein

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33
Q

Events that happen in both eukaryotes and prokaryotes for transcription

A

-Four types of RNA must be transcribed from DNA, (RNA primers, mRNA, rRNA, and tRNA
-RNA transcription first requires the enzyme RNA polymerase and it occurs in three steps
1. initiation
2. elongation
3. termination

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34
Q

What are the four types of RNA that must be transcribed from DNA

A

RNA primers, mRNA, tRNA, rRNA

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35
Q

What are the three main steps in RNA transcription

A
  1. Initiation
  2. Elongation
  3. Termination
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36
Q

Initiation

A

starting transcription require a promoter sequence and a RNA polymerase to begin
-also requires mRNA, small rRNA subunit, a start codon (AUG), and transfer RNA delivering methionine with the tRNA anticodon UAC

37
Q

Elongation

A

needs RNA polymerase and nucleotides
-adds the large subunit of rRNA and multiple tRNA’s deliver the amino acid to the initiation complex above

38
Q

Termination

A

needs a terminator sequence to end
-needs a stop codon sequence

39
Q

What do you need for transcription and translation

A

mRNA, tRNA, Ribosomes

40
Q

Transcription for Eukaryotes only

A

-most RNA transcription occurs in the nucleus but transcription occurs in mitochondria and chloroplast
-there are at least three types of RNA polymerases
-numerous transcription factors are involved
-mRNA is extensively processed before translation (for protection)
-goes through 5’ capping (Guanine), 3’ poly A tail (adenine), and splicing (removal of introns)

41
Q

transcription factors

A

-alert RNA polymerase

42
Q

Transcription for prokaryotes

A

-occurs in the nucleoid region of prokaryotes within the cytoplasm and no processing of the mRNA

43
Q

Introns

A

-are unnecessary regions that need to be removed, do not code for proteins

44
Q

Where are proteins transcribed?

A

ribosomes

45
Q

exons

A

-expressed sequences

46
Q

Events in translation for both Prokaryotes and Eukaryotes

A

-they both have initiation, elongation, and termination

47
Q

Translation

A

-involves three steps that convert an mRNA sequence into a polypeptide sequence of amino acids

48
Q

Codons to know

A
  1. AUG (start)
    2.UAC (anticodon)
  2. UAG (stop)
  3. UAA (stop)
  4. UGA (stop)
49
Q

Mutation

A

-any change in the nucleotide base sequence of a genome, mutation are rare
-they are almost always deleterious and rarely lead to a protein having a novel property that improves its ability for descendants to survive and reproduce
-happen in DNA but will be reflected in RNA
-most are repaired by enzymes like base excision/ mismatch repair

50
Q

List of point mutations

A
  1. insertion
  2. deletions
  3. substitutions
    *these are the most common
51
Q

Frameshift mutations

A
  • mutation that changes the reading frame
    -can be done by insertion or deletions
    -very bad
52
Q

translocations

A

non point mutations possibly involving portions of genes or entire genes
-less common

53
Q

silent mutation

A

-mutation but protein remains the same

54
Q

missense mutation

A

A substitution in a nucleotide sequence resulting in a codon that specifies a different amino acid: What is transcribed makes sense but not the right sense.

55
Q

nonsense mutation

A

A substitution in a nucleotide sequence that causes an amino acid codon to be replaced by a stop codon

56
Q

wildtype

A

-most common form

57
Q

ionizing radiation

A
  • induces breaks in the chromosomes
58
Q

nonionizing radition

A

-induces pyrimidine dimers (Thymine dimers)
* too much UV exposure can cause these

59
Q

nucleotide analogs

A

disrupts DNA and RNA replication and cause point mutations

60
Q

List of chemical mutagens

A
  1. nucleotide analogs
  2. nucleotide-altering chemicals
  3. frameshift mutagens
61
Q

nucleotide-altering chemicals

A

results in base pair substitution mutation and missense mutations

62
Q

frameshift mutagens

A

-results in nonsense mutation

63
Q

mutants

A

-descendants of a cell that have not successfully repaired a mutation

64
Q

Positive selection

A

directly selects for mutated cells (ex: penicillin mutants)

65
Q

negative selection

A

indirectly selects for trp auxotroph, this is a multistep process

66
Q

Ames test

A

-salmonella and His+ –> His- mutants used as a mutagen “pre-screen”
-Method for screening mutagens that is commonly used to identify potential carcinogens
-if the substance causes mutations it will revert His- back to His+

67
Q

His+

A

has the ability to synthesize histamine

68
Q

His-

A

not not synthesize histamine

69
Q

Recombinants

A

cells with DNA molecules that contain new nucleotide sequences

70
Q

Vertical gene transfer

A

-organisms replicating their genomes providing copies to a descendant (normal)

71
Q

horizontal gene transfer

A

-a donor contributes part of its genome to a recipient cell
-transfer to another cell but not apart of reproduction
-happens in bacteria

72
Q

Three types of horizontal gene transfer

A
  1. transformation
  2. transduction (general and specialized)
  3. Bacterial conjugation
73
Q

transformation

A

Griffith and s.pneumoniae

74
Q

Transduction

A

a bacteriophage transfers the DNA

75
Q

general transduction

A

-the transducing phage carries random DNA segments from donor to recipient

76
Q

specialized transduction

A

toxin transfer (E.coli O157/H7)
-only certain donor DNA sequences are transferred, such as a gene

77
Q

bacterial conjugation

A

an F factor for pilus production, R factor for resistance transfer

78
Q

Griffith’s experiment observations

A
  1. observed streptococcus pneumoniae
    -injected mouse with live strain s, mouse died
    -injected mouse with heat treated dead strain s, mouse lives
    -injected mouse with strain r cells, mouse lives
    ** these are the controls
79
Q

strain s

A

-has capsule

80
Q

strain r

A
  • has no capsule
    -non pathogenic
81
Q

griffiths experiment

A

-originally trying to develop an vaccine
1.Injected a mouse with the living strain R (non pathogenic) and heat treated dead strain s cells
2. The mouse dies (this was not expected)
3. Get a culture of streptococcus from the dead mouse
4. Found living cells with capsule strain s
-concluded something from the heat treated stain s cells transformed the living harmless R strain to be pathogenic s-strain (he did not know it was DNA)

82
Q

In-vitro transformation (Griffith)

A
  1. Heat treated cells of strain s added to a test tube
  2. some cells take up DNA from the environment and incorporate it into their chromosomes
  3. transformed cells acquire ability to synthesize capsule
83
Q

What was the transforming agent in Griffiths experiment

A

-DNA, this was found out by (Avery, McCarthy, and MacLeod)
-one of the conclusive pieces of proof DNA is the genetic material in cells

84
Q

competent

A

-cells that take up DNA
-results from alterations in cell wall and cytoplasmic membranes that allows DNA to enter cells

84
Q

Steps of transduction

A

1.phage inject DNA
2. phage enzymes degrade host DNA
3. cell synthesizes new phages that incorporate phage DNA and some host DNA
4. move to a new cell and transducing phage injects donor DNA
5. donor DNA is incorporated into the recipient’s chromosomes by recombination

85
Q

Bacterial conjugation steps

A
  1. donor cell attaches to a recipient cell with its pilus, this draws the cells closer
  2. the cells contact one another
    3.one strand of plasmid DNA transfers to the recipient
  3. the recipient synthesizes a complementary strand to become an F+ cell, the donor synthesis a complementary strand to restore its complete plasmid
86
Q

E (tRNA) exit site

A

The E site serves as a threshold. It holds the tRNA without its amino acid, which is then released by ribosome

87
Q

A (tRNA) add

A

The A site binds to the incoming aminoacyl tRNA, which carries the new amino acid to be added to the polypeptide chain.

88
Q

P (tRNA) polypeptide

A

The P site holds the tRNA with the growing polypeptide chain.

Microbiology (13 decks)

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