RNA translation and transcription Flashcards
What are genes?
Sections of DNA within the nucleus of cells
What do genes contain?
The specific instructions for the sequence of amino acids required to make a protein
Where does protein synthesis take place?
Cytoplasm
What is the name of the process to go from DNA to mRNA?
Transcription
What is the name of the process to go from mRNA to a protein?
Translation
What is mRNA?
Messenger RNA
What does the base sequence of mRNA reflect?
The DNA sequence
What is mRNA complimentary to?
The DNA template
Does mRNA vary in length?
Yes
Depending on the gene
Which enzyme synthesises RNA?
RNA polymerase
What are the three things RNA polymerase needs?
A template
Activated precursors
A metal
What template does RNA polymerase prefer?
Double stranded DNA
What are the activated precursors that RNA polymerase needs?
All 4 ribonucleoside triphosphates
ATP, GTP, UTP, CTP
Which metal does RNA polymerase need?
Mn2+ or Mg2+
Does RNA polymerase require a primer?
No
What are promoter sites?
DNA templates contain promoter sites that bind to RNA polymerase and position it in the correct place to start synthesis
Where are the promoter sites found?
5’ side of the DNA
Where are the two promoter sites in humans found?
CAAT box
TATA box
Where is the CAAT box?
75 bases up
Where is the TATA box?
25 bases up
What is an exon?
The region of DNA which codes for a protein
What is a codon?
Three coding bases
What does degenerate?
Some amino acids are coded for by more than one codon
What is the start codon?
Met
What are the stop codons?
UAA
UAG
UGA
What does a ribosome do?
Makes the proteins
Generally how does the ribosome make the protein?
Uses the instructions from the mRNA to build a new protein
What is tRNA?
Transfer RNA
What is the function of tRNA?
Carry an activated Amino acid to the ribosome to add it to the chain
How many tRNA units can one ribosome hold? Why?
2
Allows the peptide bond to form between them
In translation, what is the leaving group?
tRNA
In translation, how does the peptide bond form?
Nucleophilic attack of the A site amino acid NH2 of the P site of the carboxyl group
How many nucleotides long is tRNA?
73-93
Is tRNA single stranded or double stranded?
Single stranded in the shape of a clover
Which end of tRNA is usually phosphorylated?
5’
What is the base sequence at the end of a tRNA molecule?
CCA
How is the activated amino acid attached to the tRNA?
Using an ester group to the 3’OH of the ribose unit
How is the clover shape of tRNA caused?
It hybridises to itself
What is tRNA recycled by?
A group of enzymes that recognise the specific tRNA and add a new amino acid unit called tRNA synthetases
How many different types of tRNA syntheses are there?
There is one for each amino acids
Are reactions involving tRNA synthetases specific?
yes
Highly specific reactions
Why are reactions involving tRNA synthetases highly specific?
The enzyme must be able to recognise the matching tRNA and the incoming amino acid which may only differ by a CH2 group
What are the features for unfolding of proteins?
Conformational entropy means there is more disorder
There is hydrogen bonding to water
How much energy per mole is there in unfolding proteins?
+190 kCal/mole
What are the features of folding proteins?
Hydrophobic collapse is favoured
Intramolecular hydrogen bonding
Van der Waals interactions
How much energy per mole is there in folding proteins?
-200 kCal/mole
Do proteins fold randomly?
No they don’t fold randomly
How many stages does protein folding occur in?
2
What are the stages of protein folding?
1) hydrophobic collapse to a molten globule
2) Progressive stabilisation of secondary and tertiary structure
What does secondary structure formation depend on?
The surroundings
What do secondary structures formed in the molten globule interact with?
Other nearby structures
When secondary structures interact with other nearby structures, how does this affect the structure?
It can either stabilise or destabilise
