l20 translation

8/6/2019 L20 Translation

1/20

Genetic codon

A sequence of_ ________ in mRNA thatcodes for one amino acid

Eg.___ methionine

A collection of all genetic codons is called_______ ____

With four bases, a total of__ triplet codons is

possible

Three are___ _______ codons:___ , ___ ,

___ (signal the stop of protein synthesis)

Hence,__ codons for 20 amino acids


2/20

Features of the genetic code

1. Specific

Explain:


3/20


2. Universal

Explain:


4/20


3. Redundant/degenerate

Explain:

Eg. Phe has__ codons

Ile has__ codons

Ala has__ codons

Leu has__ codons


5/20

Features of the genetic code4. Non-overlapping

Explain:

UCGGUACAGAAUCCAACAGAAUCCGGUACA

Codon 1Codon 2

Codon 3

This is the_____ (wrong/correct) reading pattern

UCGGUACAGAAUCCAACAGAAUCCGGUACACodon 1 Codon 2 Codon 3



6/20


5. Commaless

Explain: No base is wasted for__________

UCGGUACAGAAUCCAACAGAAUCCGGUACACodon 1 Codon 2 Codon 3


UCGGUACAGAAUCCAACAGAAUCCGGUACA

Codon 1 Codon 2 Codon 3



7/20

The process of_______ synthesis

The process of TRANSLATING the________language of mRNA to the______ language of

proteins

Translation


8/20

Steps in prokaryotic translation

1. _________

2. _________

3. _________4. _________


9/20

1. Activation

Amino acids are attached to the A of the____sequence at the__ end of tRNA

The product is called_____ ____ tRNA or

______ tRNA This process activates both the amino acid and

the tRNA

Enzyme for activation is_____ ____ ______________

There is______ ___ enzyme for each amino acid


10/20

1. Activation (contd.) Each enzyme recognises a specific_____ ____ as

well as its__________ tRNA

Activation is___ dependent

Extreme specificity and the proofreading ability of

the enzyme ensures fidelity of translation

Proofreading activity of the enzyme helps in

removal of mischarged amino acids from the

enzyme or the tRNA The________ tRNA is first charged with__________

which is later converted to_ ______ __________ by

______ __________ (N10 formyl THF is the cofactor)


11/20

2. Initiation Involves the assembly of the two_________

subunits, the___ RNA, the initiator tRNA withthe first amino acid (N-formyl methionine)

Initiation is aided by proteins called________

______ (3 in number :__ , __ & __ ) Initiation is___ dependent for energy

Ribosome in prokaryotes is a__s ribosome.

Made up of 2 subunits,___ and___. 50s subunit is made of___ rRNA,__ rRNA and

31 proteins

30s subunit has___ rRNA & 21 proteins


12/20

2. Initiation (contd.)

mRNA has a consensus sequence of purine

rich nucleotide bases located 6-10 bases

upstream of the start codon, called_____

________ sequence ______ has a nucleotide sequence at its 3end

complementary to Shine Dalgarno sequence


13/20

First step of initiation involves binding of the____ to___ subunit of ribosome

Shine Dalgarno sequence binds to the 16s

rRNA at the 3 end. This facilitates proper

positioning of the____ on the________ so

that translation can accurately begin on start

codon AUG

Next, the charged_______ ____ recognisesthe start codon.The_______ of tRNA binds

antiparallel to the_____ on mRNA



14/20

__ __________ subunit binds to this complexto form a complete ribosome as a part of the

________ complex

The complete ribosome has 3 sites :__

(_____),_ (________) and_ (_____ ____)

_____ tRNA leaves the ribosome from the__

site

All new tRNAs bind to the ribosome at the__

site (except the_______ tRNA which binds at

the__ site)



15/20

tRNA with the growing peptide is bound tothe__ site

Initiation is complete with the formation of

the initiation complex

Initiation complex enters the next stage -

__________



16/20

3. Elongation The next tRNA with the next amino acid

binds to the_ site of the ribosomal complex.

The enzyme________ ___________ transfers

the_____ amino acid from the_______ tRNA

on_ site to form a_______ bond with theamino acid on the next tRNA on the_ site

Now the tRNA on P-site is_____ and that on

A-site carries a_________ The whole________ moves along the mRNA

towards the__end by a distance of one

codon. This process is called____________


17/20

3. Elongation

Now the E site has the_____ ____ , P site has the

________ ____ and A site is ready to accept the

next tRNA with the next amino acid. The steps of

elongation repeat to elongate the peptide chain

Elongation is aided by proteins called_________________ (3 in number:_____ , _____ and ____ )

Elongation is___ dependent for energy

Elongation continues till__ site falls on a____codon


18/20

4. Termination Termination begins when one of the____

codons occupies the_ site

Instead of a tRNA, proteins called_______

______ bind to the stop codon (RF-1 recognises

___ and___ , RF-2 recognises___ and___) Peptidyl transferase hydrolyses the bond

between the peptide chain and the tRNA,

releasing the peptide chain free ___ causes the release of RF-1 and RF-2

The ribosomal subunits, the mRNA and the

empty tRNA dissociate from each other


19/20

Eukaryotic translation

The initiator tRNA carries________ , not N-formyl

methionine, to the P-site

Initiation factors are__ in number (__ ___ ) Ribosomes are__s with___ and___ subunits

60s subunit is made up of___ rRNA,___ rRNA,

__ rRNA and 50 proteins 40s subunit is made up of___ rRNA and 30

proteins

mRNA is___________ (polycistronic in prokaryotes)

Similar to prokaryotic translation, with the

following differences:


20/20

Eukaryotic translation (contd.)

No Shine Dalgarno sequence. 40s subunit, aidedby eIFs, binds to the 5 cap and slides down the

mRNA to reach the start codon

Elongation factors are EF__, EF___ and EF__instead of EF-Tu, EF-Ts and EF-G respectively

A single release factor,___, functions to

recognise all stop codons. Another release

factor____ functions instead of RF-3

l20 translation

Documents