Central Dogma - Transcription & Translation Flashcards
What is the primary storage molecule of genetic information?
DNA
Useful when expressed in the production of RNA and functional proteins
Genetic information stored in DNA
What is synthesized from DNA during gene expression?
RNA
What does RNA encode for?
Directions/Instructions for protein synthesis
A part of the genome that encodes for a particular functional protein
Gene
Basic components of a (prokaryotic) gene
Promoter sequence
RNA coding sequence
Terminator sequence
It is the copying of the genetic code to synthesize mRNA using DNA as a template
Transcription
Major enzyme involved in transcription
RNA polymerase
Features of transcription
- Specific base pairing
• Cytosine pairs Guanine
• Adenine pairs Uracil - Only one of DNA is transcribed
• template/anti sense strand - mRNA is synthesized in the 5’ to 3’ direction
Copy of the sense strand, only that T is replaced U
mRNA
It is essential for accurate binding of RNA polymerase to DNA and recognition of promoter sequence
Sigma factor
Binds non-specifically to DNA then migrates to the promoter sites
RNA polymerase
Initial binding of the RNA polymerase with the promoter site is called
Closed promoter complex
RNA polymerase then unwinds several base pairs
Open promoter complex
RNA polymerase then unwinds several base pairs and initially add several
Nucleoside triphosphates (NTPs)
What occurs after 8-9 nucleotides have been polymerase during initiation of transcription?
Sigma factor, dissociates from the core enzyme
Process of elongation in transcription
RNA polymerase moves along the template DNA to continue elongation of the growing mRNA chain
Hairpin formation causes dissociation of mRNA, DNA, enzyme
Rho (p)-independent termination
ATP-dependent rho-protein binds to the nascent mRNA and pulls it away from the RNA polymerase and DNA template
Rho (p)-dependent termination
Has to go out of the nucleus for translation (for eukaryotes)
Nascent mRNA
Nascent mRNA has to undergo to protect it from degradation
post-transcriptional modifications
What are the post-transcriptional processes
- Splicing (removal of introns)
- 5’ capping and 3’ Poly-A tailing
Results to multiple protein products
Alternative splicing
Purpose of 5’ capping and 3’ Poly-A tailing
To protects mRNA from the action of nucleases
It is the process wherein polypeptide chains are synthesized
Translation
Message carried by mRNA through codons is translated into a specific
amino acid
A sequence of three ribonucleotides specific for a given amino acid
Codons
Features of the Genetic code
1. Read in successive groups of three
Non-overlapping
Features of Genetic code
2. An amino acid can be coded for by more than one codon (except Met and Trp)
Degenerate
Features of Genetic code
3. Presence of starts and stop codons
Start: AUG
Stop: UAG, UGA, UAA
Requirements for Translation
- Template - mRNA
- Ribosome
- Amino acids
- tRNA
- Amino acid-tRNA synthetase
- Initiation, elongation and termination factors
Site of translation
Ribosome
Carrier of the activated amino acid
tRNA
2 Sub-unit of ribosome
Small & Large Sub-unit
A site - ensure the amino acid
Aminoacyl tRNA
P site - to connect the amino acid
Peptidyl tRNA
E site - carries another amino acid
Exit site
Adaptor that links the codons and amino acid
tRNA
Steps in Translation
- Activation
- Initiation
- Elongation
- Termination
Enzyme catalyzes the activation of amino acid
Amino acyl-tRNA synthetase
First step in the formation of the initiation complex
Binding of mRNA and small ribosomal unit (30S)
Binding of the first charged tRNA
fmet-tRNA fmet
Binding of the large ribosomal unit (50S)
fmet-tRNA fmet on the P site
Binding of the next charged amino acid
A site as entry point
Catalyzed formation of peptide bond
Peptidyl transferase
Transcription inside of
nucleus
Translation inside of
ribosome
5’ Capping has
7 methyle guanosine
3’ Poly-A Tailing
Polyadenylation
Binding of Release Factor (RF)
A site
Binding of Release Factor (RF)
A site
Recognition of stop codons
A site
A multi enzyme complex with five polypeptide chains and a loosely held
sigma factor
RNA polymerase binds non-specifically to DNA migrates to the
promoter sites