Gene Expression Flashcards
Where does transcription occur?
In the nucleus
What are the 3 stages of transcription?
Initiation, elongation and termination
What is the TATA region?
A section of DNA in the promoter region that is recognised by transcription factors which then bind to it
What type of RNA Polymerase is used in transcription?
Type 2
What type of bonds are formed to create the sugar phosphate backbone?
Phosphodiester bonds
What is mRNA capping?
Adding a guanine nucleotide to the mRNA via a 5’ to 5’ triphosphate linkage
What is polyadenylation?
The addition of lots of A bases onto the end of the mRNA.
How does polyadenylation occur?
A signal (termination) sequence is recognised by an endonuclease enzyme which cleaves the sequence and then the A bases can be added
What is splicing?
When peptide bonds are broke to remove the introns from the mRNA
What are introns and exons?
Introns are non coding DNA sequences whereas exons are coding DNA sequences.
How is translation initiated?
Special methionyl tRNA molecules recognise the 5’ cap and bind to it, allowing the 40s ribosome subunit and other proteins to bind. The complex then moves along until a start sequence is recognised and the 60s subunit binds
What enzyme forms the peptide bonds in translation?
Peptidyl transferase
How is translocation terminated?
When a stop codon is reached a releasing factor protein bind to the A site of the 60s ribosome and water is used to break the peptide strand from the tRNA
What enzyme synthesises ribosomes?
RNA Polymerase 1
What subunits are prokaryotic ribosomes made up of?
A 50s and a 30s to give a 70s ribosome
What subunits are eukaryotic ribosomes made up of?
60s and 40s to give an 80s subunit
What enzyme produces tRNA?
RNA Polymerase 3
What enzyme attaches the amino acids to the tRNA molecules?
Aminoacyl tRNA synthetase
What is the advantage of wobble bases?
There is an increased efficiency of translation as their is more flexibility of which nucleotides can bind
Which base in the codon doesn’t have to be paired correctly in wobble bases?
The third
Which additional nucleoside is found in tRNA molecules?
Inosine
What complex carries out splicing?
A spliceosome
What does tetracycline do?
Binds to the 30s subunit of bacterial ribosomes and prevents tRNA binding to the A site
What does erythromycin do?
Binds to the 50s subunit of ribosomes and prevents translocation
What does chloramphenicol do?
Binds to the 50s subunit of ribosomes and prevents peptidyl transferase
