Chapter 13; RNA Splicing Flashcards
What is a coding sequence called?
Exons, and they are expressed
What is a non-coding sequence calld?
Introns or INTeRupt coding sequences
What is the centra dogma?
Information flows from DNA to RNA to Proteins
Which organism is direct reading of amino acid sequence from DNA sequence only possible?
Only possible in bacteria and bacteriophages
In this organism, the DNA sequence coding for amino acid sequence is often interrupted by noncoding sequences?
In eukaryotes…
What type of sequence does not result in a protein being made?
Non-coding sequence
What is the region called at the very end of a gene or pre-mRNA in Eukaryotes?
Noncoding region - and it’s at the 3’ end
What is the region before the very first exon on Genomic DNA, pre-mRNA and Spiced mRNA?
The Promoter region that becomes the 5’ leader region. The key point is that all of the “introns” that started out in the genomic DNA, that went to pre-mRNA, is actually gone in spliced mRNA. The only regions that are conserved throughout are the very beginning region “promoter region/5’leader” and the “non-coding region” at the 3’ end. All of the introns in-between are gone in mRNA.
What parts of Genomic DNA would you see, if you started out with mRNA, reverse transcribed it from a certain promoter, and cloned the sequence?
You would not see any introns, just the promoter region to the end of the exons (I am not sure if the noncoding region at the 5’ end stays or not)
AVERAGE Number of introns per gene in eukaryotes, who has the greatest number?
H. Sapiens at 7.7 > M. Musculus at 7.5 > A. Thaliana > …
How many introns per gene in yeast?
1 intron per gene
What is the approximate nucleotide number in an Exon?
~150
What is the approximate number of nucleotides in an intron?
800,000
A mammalian DHFR gene’s pre-mRNA has 31kb. What would the approximate number of kb be in mRNA?
2kb..about 6% are actual coding sequences (exons)
Where is the 5’ and 3’ splice side on a gene?
The 5’ splice site is the 5’ end of the INTRON, and the 3’ splice sits is the 3’ end of the INTRON. Notes that it is named with respect to the intron only, even though that is the portion that ends up degraded in the end (mRNA).
What does “N” mean in the intron gene sequence?
“N” means any nucleotide
What does “Y” mean in the intron gene sequence?
“Y” is for a PYrimidine C/U
What does “R” mean in the gene sequence?
“R” is for a PuRine A/G
What is Y11 mean in the intron sequence?
It is the Pyrimidine TRACT, there are a lot of pyrimidines there.
Rewrite the branch point sequence YNYURAY?
(C/U)-(A/T/C/U)-(C/U)-(U)-(A/G)-(A)-(C/U)
What is the chemical mechanism of spicing?
2’OH of the A on the branch point attacking alpha Phosphorus
Why isn’t a 3’OH attacking from the A branch point?
Because it is RNA and RNA has a 2’ OH
Last slide made: This is called a “transesterification.” Why?
??
