1. Chapter 13.1 - 13.4: Transcription basics in prokaryotes part 1

lecture 5: • The central dogma and the origin of life -Chicken or egg analogy -The RNA world • Transcription of DNA -Transcription in Prokaryotes -Transcription in Eukaryotes

What is the central dogma?

Replication: DNA - information storage
Transcription: RNA - Messenger intermediate 
Translation: Protein - effector molecule 

quick recap: What is a effector molecule?

molecules or cells that selectively binds to a protein to regulate its biological activity by responding to signals

What is transcription? (think of a translator)

(which the DNA sequence of a gene is copied into RNA, serving as the first step in gene expression)

Focus on 3 types of RNA (this is in both prokaryotes and eukaryotes):

rRNA, tRNA, mRNA (ribosomal, transfer RNA, messenger RNA)

What does RNA transcription need?

a DNA template, raw material, proteins

From ONE DNA molecule, what happens?

multiple stretches of RNA being transcribed 

Transcription happens on which DNA strand?

Only one strand, but no set template or coding strand

What is the coding/non-template strand?

this is what the RNA is copying (just replace T with U)

What is the template strand?

RNA copies the codons, adding 3’ OH to the growing rna in a 5’ to 3’ direction to match the coding strand 

Genes can be transcribed on?

the top OR bottom strand of DNA, depending on the genes

What does a transcription unit include?

A promoter, RNA-coding region, and a terminator

What direction is upstream?

Left towards the promoter

What direction is downstream?

Right towards the RNA/protein coding region (ask tomorrow) 

What is a promoter?

This tells RNA where to start

What is the RNA-coding region?

a segment of a gene’s DNA or RNA that encodes for a protein (downstream!)

How does the RNA know where to start transcription?

The transcription start site (+1)

What is NOT part of your RNA transcript?

the promoter

Initiation of RNA synthesis does NOT…

need a primer

Why don’t we need a primer for RNA synthesis?

DNA polymerase can add a primer and start adding to 3’ OH until the transcription terminator site

Explain general transcription process:

at the replication bubble, DNA unwinds, new nucleotides are added to the 3’ end of the RNA molecule, and DNA rewinds as RNA moves along the RNA coding region until it reaches the termination site (next flashcard!)