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Microbiology Ch. 7

Terms in this set (63)

Griffith's experiment
an experiment carried out by Griffith using the heat-killed bacteria in mice to discover that a factor in heat-killed, disease-causing bacteria can "transform" harmless bacteria into ones that can cause disease
Avery, MacLeod, McCarty
Determined if it was DNA, RNA, or protein that was responsible for the "transformation" effect observed in Griffith's experiments
Hershey-Chase Experiment
Used radioactive material to label DNA and protein; infected bacteria passed on DNA; helped prove that DNA is genetic material not proteins
What does each nucleotide consist of?
One sugar molecule, one phosphate group and one nitrogenous base
How is the phosphate group attached?
Attached to 5' carbon of the sugar
How is the nitrogenous base attached?
Attached to the 1' carbon of the sugar
What pairs with Adenine (A)?
Thymine (T)
What pairs with Cytosine (C)?
Guanine (G)
How is DNA packaged for bacteria?
a single circular chromosome
How is DNA packaged for archaea?
a single circular chromosome packaged around histone proteins
How is DNA packaged for eukarya?
multiple linear chromosomes packaged around histone proteins
Why is D. radiodurans and exception to the DNA packaging?
may possess 4 to 10 stacked copies of its genome
DNA replication is a ___________ process.
semiconservative
What does semiconservative mean?
each copy of DNA carries one strand of the original molecule and one newly made strand
Where does the DnaA protein bind?
oriC
What is DnaB?
helicase
What is DnaB recruited with?
DnaC - a helicase loader
What is DnaG?
primase
What does DnaG do?
lay down initial RNA primers needed for DNA polymerases to work
What is recruited to help keep the DNA unwound?
Single-stranded DNA binding proteins
What happens once the replication fork forms?
DNA pol adds nucleotides to the initial RNA primers
Initiation and elongation is virtually identical in which domains?
bacteria and eukarya
What are discontinuous lagging strands called?
Okazaki fragments
Lagging strands can be left in fragments. (T/F)
False; can't
What removes the RNA primers and fills in gaps with new nucleotides?
DNA pol I
What does DNA ligase do?
seals the sugar/phosphate backbone
Where does the termination of DNA replication occur?
ter sites
What 2 things are needed for the termination of circular chromosomes?
Tus proteins and topoisomerase
Tus proteins bind to ter sites causing what to stop?
elongation
What enzyme is needed in termination of DNA replication of a linear chromosome?
Telomerase
How is elongation stopped in a linear chromosome?
RNA primer is removed
What is a gene?
A segment of DNA that gets transcribed (copied) into ssRNA
How is RNA different from DNA?
RNA is different from DNA is three ways: (1) the sugar in RNA is ribose not dioxyribose; (2) RNA is generally single-stranded and not double-stranded; and (3) RNA contains uracil in place of thymine.
Where does the basic process of transcription start?
promoter
What separates the DNA and lays down a complementary strand of RNA?
RNA pol
Besides separate DNA, what does RNA pol do?
reads the template strand of DNA
What do sigma factors bound to RNA pol enzyme direct to a promoter?
holoenzyme
What is Rho-dependent termination?
rho protein follows RNA pol and pops it off the DNA when it reaches a termination sequence
What is rho-independent termination?
DNA sequence transcribed forms an RNA hairpin loop structure that causes the RNA pol to dissociate from the DNA
Where is the information contained that is decoded to form proteins?
mRNA molecule
Which part of the process is the most energy-intensive and is very tightly controlled and regulated?
translation
What are codons?
mRNA nucleotide triplets
Where are peptide bonds formed?
between amino acids
What is the phenomenon "wobble"?
the codon on the mRNA doesn't need to be an exact match to the anticodon
What is the start codon?
AUG
What are the 3 stop codons?
UAA, UAG, UGA
What enzyme charges tRNA?
aminoacyl-tRNA synthetase
What does the interaction between ribosome subunits and Shine-Dalgarno sequence do?
helps align all the machinery to the correct starting location
Eurkayal mRNA is usually __________, in contrast to bacterial mRNA.
monocistronic
What makes bacterial mRNA polycistronic?
multiple Shine-Dalgarno
How does translation termination occur?
When ribosomes reach a stop codon, release factors cause the complex to come apart, releasing the new protein for folding and modification
Why are molecular chaperones (chaperonins) referred to as heat-shock proteins?
they appear after exposure of cells to heat
What do molecular chaperones do?
Assist in correct folding/refolding of polypeptide sequences
What is phosphorylation or glycosylation steps, modifying the final protein structure examples of?
post-translational modification
What directs the protein to the correct location in translation?
signal peptides
What type of mutation causes no change in the amino acid sequence?
silent
What type of mutation results in coding for a different amino acid at that position?
missense
What type of mutation forms a stop codon where one shouldn't be found?
nonsense
What type of mutation inserts or deletes a nucleotide?
frameshift
Why are spontaneous mutations rare?
DNA pol proofreads
What is nitrous acid an example of?
chemical that induces mutations
How can ultraviolet light increase mutation rate in DNA?
forms thymine dimers
What mechanisms repair mutations in DNA?
mismatch repair systems
photolyase
alkyltransferase
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