RNA Flashcards
General features of RNA
5’C Single-stranded Shorter chain of nucleotides than DNA Ribose sugar Read 5’ - 3’
DNA vs. RNA
Building Blocks of RNA
- Adenine
- Thymine
- Uracil
- Guanine
RNA Transcription Base Pairing w/ DNA
What structures can RNA form?
- Primary
- Secondary
- Tertiary (fold like proteins)
What are the major differences in DNA and RNA structures?
DNA
- Long chains, compacted, stored as chromosomes
- Double-stranded
- Deoxy ribose sugar
RNA
- Short-chains
- Very unstable
- Single-stranded
- Ribose sugar
- Actions similiar to proteins (enzymatic activity)
- Complex structures
Transcription
- DNA –> RNA
- ex. copying from a book in the library
- using the same language
- mRNA converted to protein in the nucleus
*
What are the 3 steps in RNA transcription?
- Initiation
- Elongation
- Termination
What are the steps involved in the initiation step of RNA transcription?
- Find location where to start reading DNA
- Start signal comes from the promoter region
- Transcription unit (location of the gene that is being transcribed)
What is the function of the promoter region in RNA transcription?
- 1st step in initiation
- “TATA” Box
- Gives the “start here” signal
- An essential part of DNA but is not transcribed
What is the function of RNA polymerase?
- Key enzyme in transcription of DNA to mRNA
- Reads one strand of DNA and builds mRNA
- Only binds when there are specific transcription factors present in the promoter region
- Part of the initiation step of RNA transcription
- No primers or primases required
- Untwists the DNA strands on it’s own
Once RNA polymerase binds, it can only synthesize mRNA in the _________ direction.
- 5’ to 3’
- Using the non-template DNA strand to copy the template DNA strand in the 5’-3’ direction
Once transcription factors and _____ are in place, RNA polymerase can bind _____ at the correct place to begin transcript of the _____
Promoter region
DNA
Gene
What are the steps to Initiation of DNA transcription?
- Transcription factors bind to the promoter region
- RNA polymerase binds to the promoter region, where TF is bound
- DNA strands begin to unwind
- RNA polymerase initiates mRNA synthesis
What are the steps involved in the ELONGATION step of DNA transcription?
- RNA polymerase untwists and seperates the DNA
- RNA nucleotides enter and pair with DNA template
- RNA polymerase binds nucleotides to the 3’ end of the DNA molecule
- New RNA molecule peels away from the DNA and the double-helix reforms
What are the steps involved in the TERMINATION part of DNA transcription?
- Ends of the genes are recognized by RNA polymerase
- RNA polymerase just falls off
- Resulting transcript: pre-mRNA
Describe 3 Methods of RNA Processing in Eukaryotes (post-transcriptional modification)
- Methylation (addittion of a 5’cap to pre-mRNA
- Poly-adenylation to 3’ end of pre-mRNA
- RNA Splicing
Methylation (Alteration @ end of pre-mRNA)
- Stabilize RNA
- Create a target for mRNA
- Adding a CH3 group to the 5’ end of phosphate group
- “Add a methylated 5’ cap to the end of mRNA”
- Increased stability
- increased chances of translation to protein
Why is RNA processing necessary in animal cells?
- Need to be able to control when/where proteins are produced
- Can have lots of RNA without having lots of protein
Polyadenylation
- 1 of 2 methods of post-transcriptional processing methods.
- Addition of a poly-A tail to 3’ end of a pre-mRNA
RNA splicing
Removal of introns from pre-mRNA transcript (non-protein coding sequences)
Result: summation of exons (coding sequences) in mature RNA transcript that will eventually become a protein
Done by splicesosomes
Introns
- Non coding sequences on an pre-mRNA transcirpt
- “non-coding” = doesn’t code for a protein
- Removed from pre-mRNA
- Vary in size (50 bp - 3000 bp)
Spliceosomes (who, what, where)
- Complex of proteins and several small ribonuclear proteins (rRNA)
- Recognize splice sites (specific RNA sequences)
- Job: remove introns and connect exons (coding region)
Evolutionary significance of RNA splicing and introns- describe.
- Variety of options for survival
- RNA splicing allows for the potential variety in proteins produced from splicing a single pre-mRNA
- Various combinations of exons
- Increased potential in the number of proteins that an organism can produce.
- Increases adaptive potential
