Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
39 Cards in this Set
- Front
- Back
|
What are the differences b/e DNA and RNA?
|
1. RNA has a hydroxyl group on the 2' carbon of the sugar
2. DNA uses thymine (T), RNA uses Uracil (U) 3. RNA typically exists as a single-stranded molecule |
|
|
What is the importance of the single-stranded form of RNA?
|
1. Allows for precise structural and catalytic functions
2. Allows folding into particular shapes similar to a polypeptide chain |
|
|
What codon does a open reading frame start w/ in most species?
|
ATG
|
|
|
What are the classes of RNA?
|
ribosomal RNA (rRNA)
transfer RNA (tRNA) messenger RNA (mRNA) |
|
|
What is the shine-dalgarno sequenec?
|
EXCLUSIVE TO PROKARYOTES!!!
SD sequence pairs w/ a pyrimidine-rich sequence in 16s rRNA to facilitate the initiation of protein synthesis |
|
|
What is the difference b/e prokaryotic and eukaryotic mRNA?
|
prokaryotic mRNA has multiple coding sequences that are separated by non-coding sequences.
eukaryotic mRNA has only one coding sequence |
|
|
What protein is responsible for transcription of DNA into RNA?
|
RNA polymerase
|
|
|
What is the start codon?
|
RNA: AUG
DNA: ATG |
|
|
What are the stop codons?
|
RNA: UAA, UAG, UGA
DNA: TAA, TAG or TGA |
|
|
What does Uracil bind to?
|
Adenine
|
|
|
What does guanine bind to?
|
Cytosine
|
|
|
What does adenine bind to in RNA?
|
Uracil
|
|
|
What does the shine-dalgarno sequence base-pair with?
|
a pyrimidine rich sequence in 16s rRNA to facilitate initiation of protein synthesis
|
|
|
What kind of RNA synthesis does not require a primer?
|
de novo synthesis
|
|
|
What is the multisubunit structure of RNA polymerase?
|
alpha2 beta, beta-prime, omega, sigma
|
|
|
What subunit does the RNA polymerase holoenzyme lose to give the core enzyme?
|
sigma subunit
|
|
|
What is the function of the sigma subunit in a RNA polymerase?
|
To recognize the promoter locus
|
|
|
What is the function of sigma-70?
|
promotes transcription of most genes
|
|
|
what is the function of sigma-32?
|
promotes transcription of heat shock genes
|
|
|
what is the function of sigma-28?
|
promotes transcription of the flagellin gene
|
|
|
what is the function of sigma-54?
|
synthesized to assimilate nitrogen during nitrogen starvation
|
|
|
What is a processive RNA polymerase?
|
A single RNA polymerase makes multiple types of RNA (rRNA, tRNA and mRNA) in prokaryotes
|
|
|
What are strong promoters? weak promoters?
|
strong: Frequent initiation of transcription ~ every 2 seconds
weak: may contain substitutions, transcribed every 10 min. |
|
|
Where is the consensus sequence in prokaryotes? eukaryotes?
|
prok: 25 and 10 bp's upstream (towards 3' end) of the start of transcription. (-30 =TTGACA; -10 = pribnow box, TATAAT)
euk: TATA box lies 25 bps upstream |
|
|
What is the promoter locus?
|
A DNA segment that signals the start of RNA synthesis.
|
|
|
What are consensus sequences?
|
Prokaryote promoter regions contain many sequences in common called consensus sequences. These are rich in AT base pairs
|
|
|
When does the sigma subunit leave the holoenzyme?
|
Sigma separates from the core once a few phosphodiester bonds are formed b/e the holoenzyme and the promoter.
|
|
|
What is the importance of the 5' cap in mRNA?
|
essential for efficient pre-mRNA splicing, export, stability and translation initiation.
Also protects the RNA from 5'-exonucleolytic cleavage. |
|
|
What are exons? introns?
|
Exons = Coding regions-expressed sequences
Introns = noncoding regions-intervening sequences. |
|
|
What is the final step in the synthesis of mRNA molecules?
|
ligation of the poly-A tail. (AAUAAA)
|
|
|
What is the importance of the poly-A tail?
|
Essential to protect the RNA from 3' hydrolytic enzymes
|
|
|
What adds the AAUAAA hexamer to the 3' end of mRNA?
|
CPSP (cleavage and polyadenylation specificity factor)
|
|
|
What protein is added to mRNA once it has been correctly spliced and polyadenylated?
|
nuclear export receptor (NER)
|
|
|
What do termination sequences contain in mRNA?
|
1. palindromes: the RNA transcript forms a hairpin turn which disrupts the DNA-RNA hybrid (rho-independent)
2. rho-dependent: the rho protein binds to RNA and catalyzes dissociation of the polymerase from the DNA-RNA hybrid. |
|
|
What is the function of the omega subunit of RNA polymerase?
|
RNAP assembly
|
|
|
What does the core enzyme of RNA polymerase lack?
|
specificity, it cannot recognize the promoter region on the DNA template
|
|
|
What does the holoenyme of RNA polymerase do?
|
enables RNA polymerase to recognize promoter regions on the DNA.
|
|
|
What is Rifampin useful for?
|
An antibiotic that is useful in the treatment of TB by inhibiting RNA synthesis
|
|
|
What does Dactinomycin?
|
aka "actinomycin D" was the first antibiotic to find therapeutic application in tumor chemotherapy. It binds the DNA template and intereferes w/ the movement of RNA polymerase along the DNA.
|
