8.4: Protein Synthesis, transcription+splicing Flashcards
Transcription
Process of making pre-mRNA using part of the DNA as a template
How are nucleotide bases exposed
step 1
An enzyme acts on the specific region of the DNA causing the two strands to separate = nucelotide bases exposed
Template strand
step 2
(The nucleotide bases on one of the two DNA strands)
pair with complementory nucleotides from the pool in the nucleus
Role of RNA polymerase
step 3
joins the nucleotides together - pre mRNA molecule
pre-mRNA
step 4
as pre-mRNA strand is made
the DNA rejoins behind it
stop triplet code
step 5
When the RNA polymerase reaches the stop triplet code, it detaches = pre mRNA complete
Splicing
of pre-mRNA
the removal of intervening introns and the joining exons
= mRNA
mRNA molecules leave through nuclear pores
Exons
code for protein
useful
Introns
prevent synthesis of a polypeptide and intervene
not useful
No splicing occurs in …
why
prokaryotes as there are no introns in prokaryotic DNA