Introduction to Molecular Biology 4 Flashcards
(30 cards)
How does mRNA leave the nucleus?
Through nuclear pores.
What is the nuclear pore usually blocked by?
Disordered proteins.
Is nuclear export an energy dependent process?
Yes indeed.
How is genetic information read?
In triplets of three or codons.
What does degenerate mean?
One amino acid can be coded for by more than one triplet.
What does a deletion or insertion mutation result in?
A frame shift resulting in a nonsense mutation.
What does a substitution of bases result in?
A point mutation resulting in a missense mutation.
How do silent mutations arise?
Degenerate nature of genetic code means that some mutations do not change the AA sequence.
What is polymorphism?
A minor change in the DNA sequence that is present in less than 1% of the population.
What is the starting point of the read information called?
The initiation codon, at the 5’ end.
What is the end point of the read information called?
The stop codon, at the 3’ end.
What is the adaptor between the codon and the specific AA?
Transfer RNA.
What pairs with the AA in the cytoplasm?
The anti codon loop of the tRNA base pairs with the codon of an mRNA.
What is an aminoacyl-tRNA synthetase?
An enzyme that attaches the appropriate AA onto its tRNA.
How does the right AA get added to the right tRNA?
20 different aminoacyl-tRNA synthetases, each one recognises only one AA and all its compatible tRNAs.
What is always the starting codon and AA?
AUG and methionine.
Describe the structure of the tRNA-AA bond.
AA esterified to the 3’ OH of the terminal adenosine of the tRNA.
What are the properties of large subunits of RNA?
Catalytic.
How does the ribosome bind to mRNA and tRNA?
One binding site for mRNA and three for tRNA.
What three stages does translation occur in?
Initiation, elongation and termination.
What is required for initiation?
Initiator tRNA and initiation factors.
What does the initiator factor bind to?
The cap on the 5’ end of the mRNA.
What is the second step of initiation?
Peptide bond between carboxyl of tRNA at P site to amino group at A.
What is the first step of translocation?
The large subunit of the ribosome translocates along the mRNA.
