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Microbiology > Genes and DNA > Flashcards

Genes and DNA Flashcards

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Biology 101 flashcards
1
Q

bacteria do not have a

A

membrane-delimited nuclei
DNA coalesces into a nucleoid

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2
Q

plasmids

A

replicate independently
are not part of nucleoid
transfer vertically and horizontally

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3
Q

DNA is a polymer of _______

A

nucleotides

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4
Q

DNA is made of

A

pentose sugar (ribose)
phosphate
nitrogenous base

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5
Q

DNA is read

A

3’ to 5’

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6
Q

DNA is built in which direction

A

new strand always 5’ to 3’

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7
Q

DNA replication in bacteria

A

starts at origin of replication
bi-directional
replication forks
forms replication bubble
proceeds in both directions until reaches the terminus

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8
Q

DNA replication process

A

gyrases relaxes supercoils
helicases separates strands
leading stand
lagging strand
requires a free 3’ OH

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9
Q

leading strand

A

continuous synthesis towards replication fork

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10
Q

lagging strand

A

discontinuous synthesis away from fork

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11
Q

discontinuous synthesis

A
  1. RNA primase generates RNA primer
  2. Pol III synthesizes DNA from RNA
  3. Pol I removes RNA primers, replaces with DNA
  4. DNA ligase bonds 3’ OH to 5’ carbon with Phosphate
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12
Q

what happens after DNA replication

A

chromosomes must be separated by Topoisomerade IV

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13
Q

transcription in bacteria products

A

mRNA: carry genetic information
rRNA: form catalytic domain of ribosome, can act as an enzyme
tRNA: carries an amino acid and decodes codons on mRNA

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14
Q

transcription in bacteria

A

initiation:
RNA polymerase binds to promoter region with sigma factor

elongation:
RNA polymerase moves along template DNA synthesizing new RNA

termination:
RNA polymerase reaches termination sequence and leaves
new RNA is released

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15
Q

sigma factor

A

provides specificity for binding

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16
Q

two methods of transcription termination

A

rho-dependent:
Rho binds sequence on RNA, moves 5’ to 3’ down RNA, separates polymerase and RNA

stem-loop structure:
complementary base-pairing, dissociates RNA polymerase, forms binding site for termination factors

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17
Q

RNA is _____ stranded

A

single stranded but molecules base pair within themselves

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18
Q

RNA helicases reduce

A

secondary structure

19
Q

ribosomes are made of

A

proteins and rRNA
large subunit: 23S rRNA
small subunit: 16S rRNA

20
Q

16S rRNA

A

highly conserved with some variable regions
can identify bacteria genera

21
Q

tRNAs

A

carry amino acids and decode codons

22
Q

codon

A

three nucleotides that are base paired by tRNA

23
Q

anti-codon

A

three nucleotides that are complementary to a codon for that amino acid

24
Q

translation in bacteria

A

initiation:
tRNA brings first amino acid in polypeptide chain to bind to start codon on mRNA, IF1 blocks A site, IF2 selects initiator tRNA

elongation:
tRNAs bring amino acids one by one to add to polypeptide chain, P site and A site

termination:
release factor recognizes stop codon, translational complex dissociates, completed polypeptide is released, E site (exit)

25
Q

bacterial mRNA can be _______

A

polycistronic (encode many proteins)

26
Q

what does no nuclear membrane allow for

A

simultaneous transcription and translation

27
Q

bacteria genome organization

A

bacteria have operons with continuous genes under a common promoter/operator
do not have introns
regulatory element is an operator

28
Q

inducer

A

a small molecules that activates or represses an operon

29
Q

lactose operon

A

an inducible operon
repressor: blocks transcription of lac operon
inducer: binds to and inactivates repressor

30
Q

the genetic code

A

64 codons
20 amino acids
codons are: systematic or redundant
start codon: AUG
stop codons: UAA, UAG, UGA

31
Q

mutations - point mutations

A

mutation of a single base

silent: no effect on protein sequence
missense: results in an amino acid substitution
nonsense: substitutes a stop codon for an amino acid

32
Q

mutations - frame shift

A

have a deleterious effect

insertion or deletion: results in a shift in the reading frame

33
Q

what causes mutations

A

spontaneous mistakes during DNA replication
-DNA polymerases can proofread
-removes mismatched bases

chemical mutagens
-mimic a nucleoside
-modify a nucleoside
-disrupt base pairing

radiation
-causes breaks in phosphate backbone or cause two adjacent thymines to dimerize
-stalls DNA replication and transcription or leads to mismatches or frameshifts

34
Q

DNA light repair

A

photoreactivation
-uses energy of photon to break covalent bonds

35
Q

DNA dark repair

A

nucleotide excision
-nuclease cuts around dimer
-helicase unwinds the area
-DNA pol I fills the gap
-DNA ligase seals the backbone

36
Q

DNA repair base-excision and mismatch

A

base excision - removes base
mismatch - removes segment of nucleotides

37
Q

horizontal gene transfer

A

bacteria can transfer or acquire DNA from cell to cell
recipient does not have to be same genus as donor

38
Q

transformation

A

bacteria readily incorporate foreign DNA

virulence genes transfer from heat-killed smooth strain to avirulent rough strain
recovered bacteria = rough phenotype

requires competence and many genes

39
Q

conjugation

A

requires a Pilus
1. pilus of donor cell attaches to recipient cell
2. one strand of F plasmid DNA transfers from donor cell to recipient cell
3. donor synthesizes complementary strand to restore plasmid. recipient synthesizes complementary strand to become F+ cell with pilus

40
Q

transduction: introducing genes by bacteriophage

A

viruses that infect bacteria

attract parasites
lytic and lysogenic replication cycles
can pick up genes from one host and deposit them in another
highly specific

41
Q

replication by lysogenic phage

A

-phage infects cell
-phage DNA incorporated into host genome
-cell divides, prophage DNA passed on to daughter cells
-prophage DNA is excised from bacterial chromosome and enters lytic cycle
-phage DNA replicates and phage proteins are made
-new phage particle are assembled
-cell lyses, releasing newly made phages

42
Q

transduction: lysogenic phage genomes can incorporate host genes

A
  1. viral attachment and penetration
  2. integration
  3. excision
  4. infection
  5. recombination
43
Q

transposons

A

jumping genes
Barbara McClintock
gene encoding
can transfer or copy gene elsewhere in genome
can transfer surrounding sequences or genes

44
Q

transposition

A
  1. transposon encodes enzyme transposase surrounded by inverted repeat sequences
  2. transposase facilitates recombination between inverted repeats. transposon is cut from its original location and inserted into a new location

Microbiology (11 decks)

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