DNA transcription

gene expression definition

the process by which information from a gene is used in the synthesis of a functional gene product

central dogma of molcular biology

DNA (information) becomes RNA (messenger) through transcription which becomes a functional protein (worker) through translation.

3 stages of transcription

initiation, elongation, termination

transcription definition

process of creating a single-stranded RNA from double-stranded DNA

RNA polymerase II functions

catalyses phosphodiester bond formation and synthesis of RNA strands
selects the correct nucleotides based on template strand.

RNA polymerase primase function and therefore….

can initiate mRNA synthesis without a primer

Intiation

transcription factors bind to TATA box and recruit DNA pol II
DNA pol II attaches to template strand, recruits helicase to separate starnds, then begins RNA synthesis.

elongation

RNA pol II moves along template strand synthesising RNA in the 5’ to 3’ direction.
Topoisomerase removes tension by cutting, unwinding and gluing back together the DNA strand ahead.

which strand is transcribed and why?

template strand read from 3’ to 5’ to create an RNA copy of the coding strand read from 5’ to 3’

what enzymes used in transcription?

what are transcription factors?

proteins that regulate transcription

purposes of 5’ UTR G-cap

prevents RNA degradation
aids transport from nucleus to cytoplasm
promotes intron excision
acts as binding site for ribosomal subunits (translation)

purposes of 3’ UTR poly-A tail

prevents RNA degradation
aids transport from nucleus to cytoplasm

anatomy of eukaryotic genes

promotor region, coding sequence, 5’ UTR and 3’ UTR

promotor region

contains TATA box and is recognised by transcription factors/RNA pol II

coding sequence

precursor mRNA

contains introns and exons — protein cannot be made

mature mRNA

only exons — ready to be translated