Lecture 2 - RNA and Transcription Flashcards
What was the pulse-chase experiment by Zamecnik and Brenner?
- Cells exposed to radioactive uracil made RNA with it
- RNA moved from the nucleus to the cytoplasm proving that it is a messenger
- mRNA was named
What is the central dogma?
The genetic instructions carried by DNA must be transcribed into RNA, which is then translated into a protein
Who discovered the enzymes responsible for synthesising RNA and DNA?
Ochoa and Kornberg 1959
What is the sugar difference between RNA and DNA?
RNA has a ribose sugar (OH) and DNA as a deoxyribose sugar (H)
What is the base difference between RNA and DNA?
RNA has uracil and DNA has thymine
Why is RNA more chemically reactive than DNA?
It has 2 x OH groups
What are exceptions to RNA‘s usual single stranded structure?
Forming complementary base pairs creating 3D structures, non conventional base pairs (C-U)
What does Mesenger RNA do?
Codes for proteins
What does ribosomal RNA do?
Forms core ribosomal structure and catalyses protein synthesis
What do micro RNAs do?
Regulate gene expression
What do transfer RNAs do?
Adapters between mRNA and amino acids during translation
What is transcription?
RNA being synthesised for a DNA template by RNA polymerase
In eukaryotes which RNA polymerase transcribes mRNA?
RNA polymerase II
What is required for transcription?
RNA polymerase enzyme, a DNA double helix and NTP‘s (nucleotides)
In what direction is RNA synthesised?
5’ to 3’
What bond breaks between RNA and DNA once the RNA is synthesised?
Phosphoanhydride (between the 2 phosphates)
Where does the RNA-DNA helix form before its unwound and newly made RNA and double helix DNA reform?
The active site of RNA polymerase
Where does transcription occur in a eukaryotic cell?
In the nucleus
Where does transcription occur in bacterial cells?
In the cytoplasm near the DNA
What occurs to mRNA after translation in only eukaryotic cells?
Pre mRNA is turned into mature RNA in three steps
What are the three steps of mRNA processing?
- 5’ end is capped with an atypical nucleotide
- 3’ gets a tail of poly-A-nucleotides
- Introns are removed by the spliceosome which is performed by small nuclear RNA that bind to the proteins forming small nuclear ribonucleoprotein particles.
What is alternative splicing?
When more than one protein is expressed from a single gene, such as it being expressed with and without certain introns
What occurs to mature RNAs once they’re made?
They are selectively exported from the nucleus with incorrectly synthesised ones being broken down and the nucleotides being reused
What determines how much protein is translated in the cell and why?
The stability of RNA that determines how many times the mRNA itself can be translated from
