RNA DNA Proteins Flashcards
Phenotype
measurable physical/ biochemical characteristic
Bases in RNA
Adenine
Uracil (instead of thymine)
Guanine
Cytosine
RNA compared to DNA
3 points
- RNA single stranded
- Uracil instead of thymine
- no loss of O atom on sugar (Ribonucleic Acid)
Transcription
3 phases:
Initiation
Elongation
Termination
Transcription
3 essential components:
- Protein coding gene (transcribed region)
- RNA polymerase (catalyze building of RNA from DNA)
- NTPs (Nucleoside TriPhosphates. building blocks of new RNA)
Transcription
Protein coding gene
3 points
- Promoter – specific DNA sequence: transcription begins
- Coding sequence – specific DNA sequence, coding information for the protein
- Terminator – specific DNA sequence: determines the end of the RNA transcript (prokaryotes)
Transcription
RNA polymerase
2 points
- Transcription is catalyzed by RNA polymerase
2. An enzyme that catalyzes the synthesis of an RNA strand from a DNA template.
Transcription
Protein coding gene
3 points
- NTPs (building blocks of mRNA), nucleoside triphosphates
- Nucleoside = base attached to the ribose (sugar)
- 4 NTPs for each of the 4 bases:
Uridine triphosphate (Uracil, UTP)
Cytidine triphosphate (Cytosine, CTP)
Adenosine triphosphate (Adenine, ATP)
Guanosine triphosphate (Guanine, GTP)
Transcription
RNA Polymerase structure
Bacterial (prokaryotic) RNA polymerase:
2 points
- Five polypeptides (protein subunits)
a (2 copies), b’, b and (sigma) (Halo enzyme)
sigma subunit binds to DNA (promoter for initiation. opens DNA helix)
- 4 polypeptides
(sigma) subunit can dissociate (core enzyme)
catalyses transcription
Transcription eukaryotes vs prokaryotes
nucleus vs cytoplasm
Transcription
1. Initiation
2 points
- Initiation occurs at promoter
2. RNA polymerase binds to promoter and begins to unwind the DNA
Transcription
2. Elongation
3 points
- RNA polymerase moves along the DNA template
- RNA strand grows by addition of NTPs to it’s 3’ end in the unwound region
- As DNA + RNA transcript exits RNA polymerase RNA is removed from DNA template, and DNA re-winds
Transcription
3. Termination
2 points
- When RNA polymerase reaches termination site, RNA transcript is released from template
- RNA polymerase dissociates from DNA, and can perform other rounds of transcription
Similarities between Replication and Transcription
5 points
- General steps involve initiation, elongation and termination (occurring from 5’ to 3’ end)
- Both involve enzymes that synthesize a new nucleic acid strand complementary to DNA template
- Large multicomponent initiation complexes
- Adhere to Watson-Crick base pairing rules
- Both of them are highly regulated (as we don’t want mistakes)
Transcription vs Replication
4 points
- Only a portion of genome is transcribed to RNA, whereas the entire genome must be replicated or copied during DNA replication.
- Replication happens only once during cell cycle. Transcription happen over and over again at anytime (all the time)
- Transcription: Copies one strand of DNA making 1 mRNA strand but Replication: Copies both DNA strands making 2 new semi-conservative DNA strands.
- Ribonucleotides are used in transcription process instead of deoxy ribonucleotides in replication
- U replaces T as a complementary base for A in transcription
- A primer is not involved in RNA synthesis (transcription)
- RNA polymerase is used as an enzyme in Transcription whereas Replication involves DNA polymerase
- No proofreading function during RNA transcription.
- End-product: DNA has two strand while RNA has one
