Flashcards in Lecture 5 - Transcription and RNA Processing Deck (86)
Do RNA polymerases require a primer?
Does nascent RNA remain hybridized to template DNA?
Which is more permanent: RNA or DNA?
Which is more accurate: replication or transcription?
How frequent are errors during transcription?
1 per 10,000 nucleotides
Are RNA and DNA polymerases structurally and evolutionarily related?
Why do many errors during transcription go unnoticed?
Because many RNA strands are synthesized
What are mRNAs? Function?
Code for proteins
What are rRNAs? 2 Functions?
1. Form the basic structure of the ribosome
2. Catalyze protein synthesis
What are tRNAs? Function?
Central to protein synthesis as adaptors between mRNA and AAs
What are snRNAs? Function?
Small nuclear RNAs
Function in a variety of nuclear processes including the splicing of pre-mRNA
What are snoRNAs? Function?
Small nucleolar RNAs
Used to process and chemically modify rRNAs
What are scaRNAs? Function?
Small cajal RNAs
Used to modify snoRNAs and snRNAs
What are miRNAs? Function?
Regulate gene expression typically by blocking translation of selective mRNAs
What are siRNAs? Function?
Small interfering RNAs
Turn off gene expression by directing degradation of selective mRNAs and the establishment of compact chromatin structures
What is the function of other noncoding RNAs? 3 of them
Function in diverse cell processes like:
1. Telomere synthesis
2. X-chromosome inactivation
3. Transport of proteins into the ER
How are different types of RNAs synthesized?
By different types of RNA polymerases
Are both DNA strands used as templates during transcription?
How do we call the DNA strand that is not used as the template during transcription? 3 names
Nontemplate strand = coding strand = sense strand
In what direction is RNA synthesized during transcription?
5' => 3'
How is the template strand assigned?
Functional assignment: called this only when it is serving as the template, which depends on the type of RNA polymerase used and what direction it moves in which is dependent on the direction of the gene
How to tell the direction of transcription?
As the RNA polymerase moves the RNA gets longer and longer
What is a transcription bubble?
Small strand separation in which the RNA polymerase reads the DNA template strand and synthesizes RNA
How is the nascent RNA released by the RNA polymerase?
Released from a ribosomal complex on the RNA polymerase
What are the 3 types of eukaryotic RNA polymerases and what types of RNA does each synthesize? Which ones accounts for most of RNA synthesis?
I: 5.8S, 18S, and 28S rRNAs (70% of RNA synthesis)
II: mRNA, snoRNA, and some snRNA
III: tRNA, 5S RNA, some snRNA (for splicing and poly(A)), scRNA (SRP = signal recognition peptide)
Which type of RNA is regulated more finely and precisely?
What is another name for mRNA?
Pol II transcript
What are the 2 main differences between bacterial and eukaryotic RNA polymerases?
1. Bacterial RNA pol requires only 1 single protein (sigma factor) for initiation, vs eukaryotic RNA pol require many additional proteins (general transcription factors)
2. Eukaryotic transcriptional initiation must deal with the packaging of DNA in nucleosomes
Where is the promoter located? What are its 2 responsibilities? What does this mean for the sequences?
Sequence of DNA that is 5' to the initiation site of the gene: the 5' flanking region, which may also contain enhancers or other protein binding sites
Telling the RNA pol:
1. Where transcription is going to start
2. In what direction transcription should go
Therefore, the promoter is non-palindromic because DNA sequences that are non-palindromic are orientation-dependent and it is also position-dependent