Flashcards in Transcription Deck (23)
Helicase and topoisomerase:
unwind the DNA double helix
RNA polymerase 2
binds to the TATA box within the promoter region of the gene (25 base pairs upstream from first transcribed base)
synthesized from the DNA template (antisense) strand
Posttranscritional modifications include:
- a 7 - methylguanylate triphosphate cap is aded to the 5' end
- a polyadenosyl (PolyA) tail is added to the 3' end
is done by snRNA and snRNPs in the spliceosome; introns are removed in a lariat structure, and eons are ligated together
Prokaryotic cells can increase WHAT?
the variability of gene products from one transcript through POLYCISTRONIC GENES (starting transcription in different sites within the gene leads to different gene products)
Eukaryotic cells can increase WHAT?
the variability of gene products through alternative splicing (combining different eons in a modular fashion to acquire different gene products)
generating a protein is done where?
in the cytoplasm
the creation of mRNA from a DNA template
RNA polymerase I
located in the nucleus and synthesizes rRNA
RNA polymerase II
located in the nucleus and synthesizes horn (preprocessed mRNA) and some small nuclear RNA (snRNA)
RNA polymerase III
located in the nucleus and synthesizes tRNA and some rRNA
In what direction does the RNA polymerase travel?
3' --> 5'
does not proofread its work
coding strand (sense strand)
not used as a template during transcription
complementary to the template strand
Where does the RNA polymerase II bind?
the TATA box
heterogenous nuclear RNA (hnRNA)
The primary transcript that is formed when the DNA double helix reforms.
mRNA is derived from horn via post transcriptional modifications
Maturation of the horn includes:
splicing of the transcript to remove noncoding sequences (introns) and ligate coding sequences (exons) together
Splicing is accomplished by the
In the spliceosome,
small nuclear RNA (snRNA) molecules couple with proteins known as small nuclear ribonucleoprotines (snRNPS or "snurps"). The snRNP/snRNA complex recognizes both he 5' and 3' splice sits of the introns. These noncoding sequences are excised in the form of a lariat (lasso - shaped structure) and then degraded
7 - methylguanylate triphosphate cap
this is added at the 5' end of the hnRNA molecule.
This cap is added during the process of transcription and is recognized by the ribosome as the binding site. It also protects the mRNA from degradation in the cytoplasm
3' Poly - A Tail
A poly A tail is added to the 3' end of the mRNA transcript and protects the message against rapid degradation.