RNA: Transcription, Processing and Decay Flashcards
Does DNA actually do work in a cell?
No
In eukaryotes, where is the DNA and where is the protein?
DNA is in the nucleus
Protein is predominately in the cytoplasm
In ~1957, Elliot Volkin and Lawrence Astrachan made an important insight suggesting that _ was the intermediate
RNA was the intermediate
What did Volkin and Astrachan find?
A striking burst of RNA synthesis following the phage infection of E. coli
What did Volkin and Astrachan’s finding suggest?
RNA might play an important role in enabling the phage genome to act
Does uracil exist in RNA or DNA
Uracil only exists in RNA
What was the experiement and what did we find out radioactive uracil was pulsed in?
Radioactive uracil was pulsed then chased with regular uracil. The newly synthesized RNA was found to be exported into the cytoplasm.
Suggesting RNA was the intermediate
What is the ribose difference between RNA and DNA
DNA- deoxyribose
RNA - ribose
How do ribose and deoxyribose differ at the 2’ position?
Ribose has an OH group at the 2’ position and Deoxyribose has an H at the 2’ position
Is RNA double or single stranded?
RNA - single stranded
DNA - double stranded
What amino acid does RNA have insead of Thymine?
Uracil
What does uracil exhibit that thymine doesnt?
Exhibits wobble, can pair with both Adenine and Guanine
What does uracils wobble help form?
Complex secondary structures
Unlike DNA, RNA can catalyze some _ reactions
Biochemical reactions
What RNAs can catalyze biochemical reactions?
Ribozymes
Which type of RNAs are intermediates between DNA and protein?
Messenger - mRNAs
What are the RNA bases
ACGU
Adenine
Cytosine
Guanine
Uracil
What is a nucleoside? What are the 4?
Base+ribose
Adenosine
Cytidine
Guanosine
Uridine
What is a nucleotide?
What are the 4?
Base + ribose + triphosphate
Adenosine triphosphate
Cytidine triphosphate
Guanosine triphosphate
Uridine triphosphate
What is transcription?
The process of generating RNA transcripts from a DNA template
What direction does RNA transcription proceed?
5’-to-3’: the transcription’s 3’ end will terminate at the template’s 5’ end.
Can occur on either of DNAs two strands.
In what direction does RNA polymerase read the template strand?
Reads 3’-to-5’ of template so new RNA is synthesized 5’ to 3’
the _ end of an entering ribonucleotide attaches to the _ end of the growing RNA
5’ end attaches to the 3’ end
RNA polymerase catalyzes the formation of _ bonds
phosphodiester bonds
Many RNAs can be _ transcribed from the same gene
simultaneously
An RNA will be the _ _ of its DNA template?
meaning?
Reverse complement
Meaning the coding strand will have the same sequence at the non-template strand except with Us replacing Ts
What are the three steps of transcription?
Initiation
Elongation
Termination
Initiation occurs when RNA polymerase binds specific sequences called _
Promoters
Where are promoters located?
Upstream of coding regions
What happens to the space between the promoter and coding region
The space is transcribed but not translated
Transcripts _ and are extended from promoters
Initiate
Each gene or operon has its own promoter and these promoters have _ sequences
Different
In E.coli what do sigma factors do?
Sigma factors position RNA polymerase to the right motifs prior to transcription
After transcription initiates, what happens to the sigma factor.
It dissociates
E. Coli has a number of different sigma factors that facilitate transcription of different _
genes
As RNA polymerase slides along its template, DNA is _ in front and _ behind
DNA is unwound in front and rewound behind
What eventually stops transcription at most genes in E.coli?
Hairpin formation
What mechanism stops transcriptions in prokaryotes?
Rho protein
Degradation of mRNAs promotes rapid turnover of the _
Transcriptome
What is the range of half life of RNAs in E.coli
30 seconds to 20 minutes
What does pyrophosphohydrolase cleavage do?
Initiate degradation
what is Rnase E and what does it do?
It is an endouclease that binds and cleaves RNA at the A- and U- rich regions
How do you further break down mRNA fragments?
Additional rounds of cleavage and enzymes
