4.2 Central Dogma

Central Dogma

Flow of genetic information

Order of Central Dogma

DNA Replication > Transcription > mRNA > Translation > Proteins/polypeptides

Transcription

Process of Synthesizing mRNA strand from DNA template

Messenger RNA (mRNA)

Temporary copy of gene that contains information for a polypeptide formation.

(AA sequence in polypeptide)

Translation

Process of synthesizing polypeptides from mRNA information

Transcription: Promotor

Site in DNA that species/is starting spot

Transcription: Terminator

Site on DNA that specifies ending transcription

RNA transcript is complementary to which strand?

Template Strand

Transcription Factors

Proteins involved in controlling Transcription Rate

Regulatory Sequences / Elements

Regions of DNA that regulate transcription

Stages of Transcription

1. Initiation

2. Elongation / Synthesis

3. Termination

Transcription: Inititation

TFs recognizes base sequence in promoter to determine start location.

Transcription: TF and RNA Polymerase relationship

TF allows RNA poly to bind to Promoter.

Open complex is formed, allowing transcription.

Transcription: Elongation

RNA polymerase moves along DNA strand making open complex to synthesize RNA transcript

Transcription: Termination

RNA polymerase reaches termination point on DNA strand.

Transcription Start location

+1 (promoter begins)

Promoter location in Bacteria

(Sequence numbers)

-35 and -10

Consensus Sequence

Most common base pairs in a sequence.

Relationship between transcription rate and Consensus accuracy

Close to Consensus = Faster Transcription

Divergence from Consensus = slow transcription

RNA Polymerase 5 Core Enzymes

2x Alpha = Assembly/Binding

Beta = Bind DNA

Beta’ = Bind DNA

Omega = Core Enzyme Stability

• Sigma Factor, binds to core enzyme to create Holoenzyme Complex

Transcription: Sigma Factor

Recognizes Promoter → allows transcription to begin

Bacterial Transcription: Where does Unwinding Begin?

TATAAT Region (AT Base pairs break easier 2 H bonds)

Bacterial Transcription: How does Sigma Factor release

Short RNA strand is synthesized

Elongation phase begins

Bacterial Transcription: How long is the unwound section of DNA inside the moving RNA Polymerase

17 Base Pairs Long

2 Different termination mechanisms of E Coli.

Rho Dependent

Rho Independent

How does Termination Occur? (3 steps)

Short RNA-DNA Hybrid Separates inside RNA Poly

RNA transcript is released

RNA Polymerase releases from the DNA Template Strand

Rho Dependent Termination

rut (Rho Utilization Site) is synthesized and travels along the RNA transcript to disassociate RNA polymerase and cut RNA transcript.

Bacterial Transcription: What causes RNA polymerase to pause?

Hairpin loop synthesized in RNA transcript after reaching termination point on template strand.

Intrinsic Termination

Rho Independent Termination

RNA Transcript Stem Loop pauses RNA Poly

Terminator has U rich region coded for automatic RNA Transcript disassociation

Transcription: Eukaryotes vs Prokaryotes

(3 differences)

1. Larger Genome Size (more protein-coding genes)

2. Compartmentalized Organelles

3. Multicellularity (Transcription of correct gene, cell type, right time)

Basal Transcription Apparatus

GTFs D,B,F,E,H + RNA Poly II complex on top of TATA box start sequence.