translation

1. •What is Translation ?
•Initiator tRNA
•Ribosome
•Translational Unit
•Untranslated Regions

2.  The process by which the triplet codon (base
sequence) on mRNA guides the linking of a
specific sequence of Amino acids to form a
polypeptide chain on Ribosome is known as
Translation (under central Dogma)

4.  Francis Crick proposed that tRNA act as adaptor
molecule ,which could read the code and would
bind to specific Amino acids during translation .
This mechanism was explain under Adaptor
hypothesis.
 tRNA was known before Genetic Code .
 tRNA is also known as soluble RNA(sRNA)
 The tRNA has a secondary structure like clover
leaf ( explain by clover- leaf model)
 tRNA has five arms:
 Anticodon loop,Amino acid acceptor end, T-loop,
D- loop & Variable loop.

7.  The organelle where the process of translations takes place.
 Ribosomes are small, dense, rounded and granular particles of
Ribonucleoprotein.
 They found freely in the matrix of Mitochondria, Chloroplast and
Cytoplasm.
 Or remain attached with the membranes of Rough ER and Nucleus.
 It provide the ordered interaction of all the molecules involved in
protein synthesis.
 Tissieres and Watson (1958) isolated 70S E.Coli ribosome, which cosists
of two subunits :-50S and 30S.
 Ribosome contains ¾ kinds of RNAs and Proteins
 Dimer:-Two ribosomes become associated with each other by high
concentration of Mg++ ions in matrix.
 During protein synthesis many ribosomes are aggregated due to
common mRNA and form Polysomes or Polyribosomes.

12.  70S Ribosome:
 50S +30S subunit
 70S contains: Three types of rRNA
 50S : 23 S and 5 S rRNA + 120 nucleotides.
 30S : 16 S rRNA + 1650 nucleotides.
 About 60% of rRNA is helical and contains paired
bases.
 These paired bases region is due to hairpin loops
between complementary regions of their molecules.

14.  It is the sequence of RNA flanked by the start codon
AUG and the stop codon in mRNA.
 It codes for polypeptide that has to be produced.

15.  These are some additional sequences in an mRNA
that are not translated.
 They are present at both the ends ,that is 5’end
(before start codon ) and at 3’end (after stop codon).
 They improve the efficiency of translation process.