Exam 2 Flashcards
(29 cards)
What are the differences between RNA and DNA?
RNA has uracil instead of thymine
RNA has ribose instead of deoxyribose
RNA is single stranded
What is similar in RNA and DNA?
Both have a 5’ to 3’ phosphate backbone
Discuss RNA being single stranded
Although RNA is single stranded, it can bind to itself with hydrogen bonds between complementary sequences. When it does this, it can create secondary structures that improve its stability.
Types of RNA
mRNA (messenger RNA) = coding RNA
tRNA(transfer RNA) =carries amino acids to the ribosome and interacts with mRNA
rRNA (ribosomal RNA) = component of the ribosome
miRNA (micro RNA) = regulation of translation
circRNA (circular RNA) = circular molecule that perform a large variety of functions including some coding.
Which RNA types discussed are considered non-coding RNA and what is usually their purpose?
tRNA
rRNA
miRNA
circRNA *exception- small amt of coding possible
Non-coding RNA is usually involved with the regulation and controls of transcription and translation.
What are some secondary structures RNA can form?
bulge internal loop hairpin junction tetraloop = C(UUCG)G pseudoknot
How does RNA increase its stability?
base pairing with itself forming secondary structures H bond between base and phosphate backbone (tetraloop) base stacking (tetraloop) Uracil can base pair with guanine
Why is uracil binding with guanine not an issue for RNA as it would be for DNA?
RNA has already been coded for and is single stranded so the nucleotide sequence is not changed.
Example of RNA as an enzyme
RNAse P
RNAse P function
- endoribonuclease
- small portion made of protein but mostly RNA
- cleaves pre-tRNA precursor to create mature tRNA
RNA Pol I
encodes for rRNA large subunit
RNA Pol III
encodes for small rRNA subunit & tRNA
RNA Pol II
encodes for mRNA
transcription of rRNA
ribosomal RNA is heavily transcribed and thus multiple RNA Polymerases are present to transcribe several rRNA simultaneously
Template strand
The strand of DNA that the RNA is transcribed from that is complementary to the RNA sequence
Coding strand
DNA strand that has the same sequence as the RNA except thymine is replaced with uracil
Pol IV and Pol V
RNA polymerases that encode for siRNA
What is a promoter and what is essential to it?
the sequence where RNA polymerase first binds to transcribe a gene
- It is directional 5’ > 3’
- On the template strand that is being transcribed
- near the start site (either upstream or very near downstream)
- key to regulation as it can determine how often and with what affinity a polymerase binds to it to start transcription
- contains the core promoter sequence in eukaryotes
Terminator
sequence that determines where transcription stops
Transcription steps
- Initiation
- Elongation
- Termination
RNA Polymerase II core promoter elements
short DNA sequence of around 40 bp with one or two sequence elements either upstream or just downstream of start site. These elements could be:
- TATA-box
- Inr : Initiator element
- TFIIB- binding element (Inr)
- downstream promoter element (DPE, DCE, MTE)
Pre-initiation complex
- TFIID
- TBP
- TFIIA
- TFIIB
General transcription factors required for in vitro transcription
- TFIID
- TBP
- TFIIA
- TFIIB
- TFIIE
- TFIIH
TFIID
Recognizes TATA box promoter sequence