Bacteriology: Ribosome and Unusual Modified Nucleotides

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  • Topic: Ribosome, RNA, DNA
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  • Published : May 24, 2013
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What are the 2 antibiotics that affect transcription?
Rifamycin B
Actinomycin D

What does Rifamycin bind to?
Selectively binds to bacterial RNA polymerase and inhibits initiation

What does Actinomycin D bind to?
Nonselectivly binds to DNA and inhibits elongation.

Rifomycin B is used to treat tuberculosis and leprosy.

Actinomycin D is an anti-cancer drug which mimics and DNA base and blocks transcription elongation. Can inhibit DNA synthesis in normal cells.

List all types of RNAs:
mRNA: encodes proteins
rRNA: forms scaffolding on which ribosomes are built
tRNA: Shuttles aa to ribosomes
tmRNA: frees ribosome stuck on damaged mRNA
catalytic RNA: carries out enzymatic reactions

which RNA is the easiest to degrade by RNases and why are the other 2 more stable? mRNA has a short life and is easily degraded.
tRNA and rRNA are more stable due to their folded structures and presence of unusual modified nucleotides.

What is the central dogma?
DNA –DNA replication DNA-transcription mRNA—translation-> proteins

How many possible codons are out there?
64; 61 specify amino acids, 3 are stop codons

What is wobble?
When tRNA can recognize more than one codon at a time and it only base pairs with the first 2 positions of the codon and has an irregular base pairing at the 3rd position. This mismatch is called wobble.

What makes tRNAs so stable?
The unusual modified nucleotides.

What are the 2 regions of tRNA?
1)anticodon loop: where anticodon hydrogen bonds with codon on mRNA 2) 3’ CCA (acceptor end) : where amino acid binds

What enxymes carry out the charging of tRNA?
Aminoacyl tRNA synthetases.
What is ribosomes structure?
2 subunits: each subunit contains rRNA and proteins.
Prokaryotes: 50S subunit +30S = 70 S ribosome
30S = 16S rRNA molecule and 21 proteins
50S = 5S, 23 S and 31 proteins
* How do you build a ribosome?
Its initially transcribed from a single RNA molecule
Specific RNAses cleave the transcript...
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