aka transcription

video (basic) – video (advanced)

http://www.nature.com/scitable/definition/transcription-dna-transcription-87

http://www.nature.com/scitable/topicpage/dna-transcription-426

https://www.wikiwand.com/en/Transcription_(genetics)

Transcription initiation

Initiator sequence

Many factors.... Helps with helicase activity. phosphorelates the enzyme (activates it)

• TFIIH
• Transcription factors
• Promoter region. The composition and size of the promoter region affects the probability of that gene bing transcribed.

RNA polymerase levels and ribosome leves is affected by cell growth rates. This affects gene expression.

Transcription elongation

• Capping the pre-mRNA. The cap binding complex is recognized by nuclear pores to let the completed mRNA out of the nucleus.
• Polyadenylating the pre-mRNA, like telomeres for mRNA... determines its half-life.

RNA polymerase

Eukaryotes

• RNA polymerase
  • Pol I makes Ribosomal RNA
  • Pol II makes Messenger RNA
  • Pol II makes Transfer RNA
  • Pol IV and V, only in Plant cells

Prokaryotes

Only one type of DNA

Function

• First unwinds the DNA (helicase activity)
• Transcribes 3' to 5' end to create a 5' to 3; precursor mRNA strand
• DNA/RNA hybrid is separated at an archway.

Pre-mRNA processing - splicing

One Gene that can code for multiple variants of the Protein.

• Exons, and Introns
• snRNA
• splicesome. See video RNA splicing mechanism.

mRNA stability

• Half-lives around 30min to 10 hours.

Transcription in bacteria

Much simpler. transcription, and translations coupled. Can code several proteins at the same time, operon.