POST TRANSCRIPTION
It is a set of biological processes common to most eukaryotic cells.
WOBBLE HYPOTHESIS is the base pairing that occurs between nitrogen bases.
2. POST TRANSCRIPTIONAL MODIFICATION
• It is otherwise called as co-transcriptional modification.
• It is the process in eukaryotic cells where primary transcript RNA is
converted into mature RNA.
• A notable example is the conversion of precursor mRNA into
mature mRNA that occurs prior to protein translation.
5. 5’ CAPPING FORMATION
• The 5’ end of the pre- mRNA is altered by the attachment of
guanosine nucleotide via the special link 5’-5’- triphosphate
linkage.
• The guanosine nucleotide quickly methylated at the 7’ position
to form 7- Methyl guanosine.
• One important function of this cap is to protect mRNA from
degradation during protein synthesis.
7. 3’ POLYADENYLATION
• The 3’ end of pre- mRNA is removed and a series of
adenosine nucleotide are added.
• The 3’ end tail that contains many adenines called poly (A)
polymerase (PAP), which contains 250 nucleotides.
• The poly (A) tail also provides the mRNA with stability and
keeps the tail from degrading.
9. RNA SPLICING
• Splicing is the editing of the nascent pre- mRNA into a mature
mRNA.
• Splicing is catalysed by the spliceosome.
• Not all regions of the pre- mRNA molecule code for proteins.
The regions that do code for proteins called exons.
• Before the pre- mRNA exits the nucleus, special protein will
cut out the introns and splice together the exons.
• SnRNA is the important protein molecule present in it.
11. WOBBLE HYPOTHESIS
• Wobble hypothesis is different variation of basepair between
the different base analogs in RNA.
• Crick (1996), proposed the wobble hypothesis to explain the
degeneracy of the genetic code.
• There are 61 codons that synthesize aminoacid. Each codons
have particular aminiacid.
• The total number of tRNAs is less than 61.
12. • According to the wobble hypothesis only the first and second
base of the triplet codon on 5’- 3’ mRNA pair with the bases of
the anticodon of tRNA.
• The conventiomal pairing (A=U), (G=C) is known as watson-
crick pairing and the second abnormal pairing is called wobble
pairing.
• The anticodon of yeast alanine- tRNA contains the nucleoside
inosine.
13. ANTICODON
tRNA
CODON
mRNA
A U
C G
G C/ U
U A/ G
I A/ C/ U
• Due to the wobble base pairing one tRNA becomes able to
recognise more than one codons for an individual aminoacid.
14. DNA triplet, mRNA codons and tRNA anticodons showing
watson- crick pairing.
15. Wobble pairing of one glycine tRNA with three codons of
mRNA due to wobble in 5’ 3’ direction.
