Polypeptide synthesis Flashcards
What is the basic sequence for protein synthesis?
DNA provides the instructions in the form of a long sequence of bases.
A complementary section of part of this sequence is made in the form of pre-RNA (transcription).
Pre-RNA is spliced to form mRNA.
mRNA is used as a template to which complementary tRNA molecules attach and amino acids they carry are linked to form a polypeptide (translation).
What is the function of DNA helicase?
It acts on a specific region of the DNA causing the two strands to separate, which exposes the nucleotide bases.
What does the template strand do? Transcription.
It pairs with complementary free nucleotides from a pool in the nucleus.
Job of RNA polymerase.
In transcription, it moves along the strand joining the nucleotides to form pre-messenger RNA (pre-mRNA).
When does transcription stop?
When a stop codon is reached.
Why are only 12 bases exposed at one time?
To reduce the chance of DNA being damaged.
What happens in splicing?
Introns are removed and exons are joined.
What happens between splicing and translation?
mRNA leaves the nucleus through nuclear pores, it becomes attached to ribosomes ready for translation.
What happens during translation?
A tRNA with complementary anticodon to codon, pairs with the codon, a second tRNA molecule does this and their amino acids are joined by a peptide bond. This requires ATP and is catalysed by an enzyme.
