RNA Processing Flashcards
Colinearity
In prokaryotes, the coding region of a gene is uninterrupted
The sequence of the gene corresponds to the amino acid sequence
They are colinear
Number of nucleotides is proportional to the number of amino acids (3:1)
3 primary regions of mature mRNA
5’ UTR
Protein coding region
3’ UTR
5’ UTR
5’ untranslated region
Does not code for amino acids
Binds the ribosomal complex
Protein coding region
Comprises the codons that specify the amino acids
Begins with a start codon and ends with a stop codon
3’ UTR
3’ untranslated region
Does not code for amino acids
Affects the stability of the mRNA and regulates its translation
Where do translation and transcription occur in prokaryotes
In cytoplasm and can occur simultaneously
The mRNA sequence direction corresponds to the DNA (no processing between)
Eukaryotes rna processing
The mRNA is extensively modified before translation and must be transported out of the nucleus
Pre-mRNA
Result of Transcription of the entire template strand of the gene in eukaryotes
is then processed to make mature mRNA that can be translated into protein
How are genes interrupted
By introns
exons
are protein coding segments,
Introns
are intervening (non-coding) segments
Need to be removed by splicing
Exons - more detail abt length and order
Can vary in length and relative position on the gene
However, the order of exons is always maintained in the spliced mRNA
Where does splicing take place?
The nucleus
snRNAs
Small nuclear RNAs are required to remove the intron
Compose a spliceosomal complex
Introns
Only present in eukaryotes DNA and can vary in nucleotide length, and there are different types.
Some have self splicing capabilities as in mitochondrial jeans they are removed from pre-mRNA by the action of us places on.
What is the function of an addition of a 5 prime cap?
It facilitates the binding of ribosome to the five prime end of mRNA
increases mRNA
What is the function of the three prime, cleavage, and addition of Polly a tail?
Increases the stability of mRNA facilitates binding of ribosome to mRNA
What is the function of RNA splicing?
Removes the non-coding entrance from pre-mRNA facilitates the export of mRNA to cytoplasm and allows for multiple proteins to be produced through alternative splicing
What are the steps to add the five prime cap?
One of the phosphate groups at the five prime end of the mRNA is removed
A guanine nucleotide with its phosphate group is added
Methyl groups are added to position seven of the base of the terminal guanine nucleotide
Metal groups are also added to the to prime position of the sugar in the second and sometimes the third nucleotides, and if the base on the second nucleotide is a that basement also be methylated
For the five prime cap, methyl groups are added to what?
Seven prime position of the terminal guanine that was added
Two prime OH group of the sugar of the first and sometimes second nucleotide
To adenine if it is the second nucleotide sometimes
Can methyl guanosine be transcribed?
Nope
Three prime Polly a tail
50 to 250 A’s are added to the three prime end of the mRNA
The A’s are added without a template
This is termed polyadenylation
Poly a consensus sequence is the polyadenylation signal located 11 to 30 nucleotides upstream of the cleavage site
Poly a consensus sequence
Is the polyadenylation signal located at 11 to 30 nucleotides upstream of the cleavage site
What are the different parts of the intron?
5’ spice site - containing junction sequence GU
Branch point - conserved A residue located 18-40 nt upstream of 3’ splice site
3’ splice site - containing the junction sequence AF
Spliceosome
It’s an rna/protein structure
It contains five small nuclear RNAs (U1, U2, U4, U5, U6)
The snRNAs associate with about 300 small proteins to form small nuclear ribonuvleopriteins (snRNPs)
Spliceosome assembly
U1 attatches to the 5’ splice site
U2 attatches to the branch point A
A complex of U4, U5 and U6 joins the Spliceosome
U1 and U4 are released
Base pairing btw sequences in the mRNA and the snRNAs hood the sliceosome together
The exons are joined together and the intron is released as a lariat
Why is glucose the preferred source of energy for bacteria
It requires less energy to metabolize glucose than lactose
