What is an organisms phenotype dependent on?
The number, type and function of their cells.
Every cell in a genome has an __________ genome.
Identical.
Expression of a gene is turned ____/____ in each cell to introduce _______ types of ______.
On/Off
different
cell
A structure of a gene contains:
A promoter and a transcripitional unit.
What is a promotor?
DNA sequence that specifies where transcription begins on a chromosome.
Where is the promotor located?
upstream of the transcriptional start point of the non template coding dna strand.
what is the transcriptional unit?
The part of a gene that is copied into RNA.
What is RNA polymerase?
Enzymes of transcription that synthesize rna in the 5’-3’ direction, reads the template in the 3’-5’ direction.
RNA polymerase has no _____, and _________ helicase acitivity.
Primer
Intrinsic
What are the 3 types of eukaryotic RNA polymerase?
- RNA Pol 1: RNA
- RNA Pol 2: mRNA
- RNA Pol 3: tRNA
What is the first step transcription?
Transcriptional initiation, mediated by direct interaction of DNA binding proteins to specific regulatory sequences of the gene(Rate determining step).
Prokaryotes only have _____ RNA ___________.
One
Polymerase
What is the first type of binding protiens?
1) General trasncription factor protiens: bind to the promoter and recruit RNA polymerase 1, results in low level basal transcription.
What is step two of transcription?
- Transcription elongation: RNA polymerase moves along the template strand(3’-5’) then unwinds the DNA in front of RNA polymerase, reanneal the DNA behind the transcription bubble.
What is the second type of binding proteins?
2) Transcriptor activator proteins: bind to the enhancer regions distant from the promoter to cause DNA looping, bringing mediatpr and RNA polymerase to the promotor, results in high level of transcription.
In transcription elongation _______________ are added to the _ end of the RNA transcript.
Ribonucleotides
3’
To allow reannealing back to double stranded DNA after transcription elongation what needs to happen?
The growing RNA transcript is displaced from the DNA template strand.
What is step 3 of transcription?
- Transcriptional termination: 3 types.
What is the first type of transcriptional termination?
- Rho independent termination(prokaryotes): Intricnsic, terminator sequence in mRNA base pairs with itself to form a G-C hairpin and causes RNA polymerase to stall and disassocaite.
What is the second type of transcriptional termination?
- Rho dependent termination(prokaryotes): Terminator sequance in mRNA is recognized and bound by the Rho hilicase which unwinds the RNA from the template DNA and RNA polymerase.
What is the third type of transcriptional termination?
- Cleavage and polydenylation specificity factor-CPSF(eukaryotes): AAUAAA sequence in the mRNA signals the CPSF to bind and cleave the completed mRNA transcript signaling RNA polymerase to stop transcription.
What are two similarities between DNA replication and transcription?
- Both synthesize in the 5’-3’ direction.
- Both have an elongation reaction, however DNA replication uses dNTP’s and transcription uses NTP’s.
What are the 3 main ways DNA replication and transcription are different?
- DR replicates entire genome(one cell per cell cycle), T sythesizes RNA at a particular gene(multiple copies of RNA).
- DR needs a primer, T does not.
- In DR new DNA strand remians base paired with the template(double stranded), in T RNA is released from the template strand(single stranded).
In both euklaryoptic and prokaryotic cells mRNA ends are ____ _________.
Not translated.
