protein synthesis Flashcards
What are the steps of transcription
A transcription factor binds to the promoter region
The DNA is unzipped by helicase enzyme.
Then RNA polymerase binds just before the start of the codon
Free activated RNA nucleotides pair up with complimentary bases on the template/ antisense strand.
The sugar phosphate group of these RNA nucleotides are then bonded together in a reaction catalysed by RNAS polymerase to form the sugar-phosphate backbone of the mRNA.
RNA polymerase then moves along the template strand in the 3’ to 5’ direction so therefore mRNA grows in the 5’ to 3’ direction
mRNA stops being transcribed when it reaches the stop codon
Then mRNA leaves the mRNA molecule leaves the nucleus through a nuclear pore.
mRNA has the same bases as the coding strand but U instead of T
What are the steps of translation?
It occurs in the cytoplasm of the cell
mRNA attaches to a ribosome
tRNA molecules bind to their specific amino acids and bring them to the mRNA molecule on the ribosome
Then the triplet of bases (anticodon) on each tRNA molecule pairs with the complimentary triplet on the mRNA molecule called the codon
AUG is the start codon and signals the start of translation and codes for methionine
Two tRNA molecules can fit on the ribosome at one time
Then a peptide bond forms between the two amino acids by condensation reaction.
Process continues until it reaches a stop codon and this signals that the mRNA molecule is complete and then the final amino acid chain forms the final polypeptide
What does it mean by the genetic code is non-overlapping?
Means that each base is only read once
The adjacent codons don’t overlap
It means that the same letter wont be used for two different codons
What does it mean by the genetic code is degenerate
It is because multiple codons can code for the same amino acid and this limits the effect of mutations
The genetic code is universal , HOW?
Almost every organism uses the same code and since the triplet codes code for the same amino acids in all living things that makes it possible for genetic engineering to happen.
