8.4 - Transcription

Cards (9)

What’s transcription ? 
The production of pre-mRNA from DNA
1st step of transcription ? 
an enzyme acts on a specific region of DNA, the strands separate, exposing the nucleotide bases
2nd step of transcription ? 
The bases on the template strand pair with complementary nucleotides in the nucleus
3rd step of transcription ?
The enzyme RNA polymerase moves along the strand and joins the mRNA nucleotides, forming phosphodiester bonds and forming the pre-mRNA molecule
4th step of transcription ? 
As nucleotides join, the DNA strands rejoin behind it (adenine on the template DNA strand bonds to uracil rather than thymine)
5th step of transcription ?
When RNA polymerase reaches a stop codon it detaches and the pre-mRNA is complete
Is pre-mRNA produced in prokaryotic cells ? 
No, transcription directly produces mRNA
What is splicing ? (Only occurs in eukaryotes) 
Pre-mRNA contains non-coding sections called introns, splicing removes these as they’d prevent the production of the polypeptide, the functional exons are joined together to form mRNA
How does the mRNA molecule leave the nucleus ? 
Leave via the nuclear pores