GENETIC CODE HISTORY AND DISCOVERY FEATURES OF GENETIC CODE IMPORTANCE DEGENERATE CODON UNAMBIGUOUS NATURE OF CODON CODON ON mRNA AND ANTICODON ON t RNA

1. GENETIC CODE
By – Dr R. K. Upadhyay
PGT, Biology

2. The genetic code is the set of rules by which
information encoded in genetic material (DNA or
RNA sequences) is translated into proteins (amino
acid sequences) by living cells.
GENETIC CODE

3. GEORGE GAMOW
 In order to code for all the 20 amino acids, the code
should be made up of three nucleotides
 Codon is triplet
 4 3 = 64 codons

4. HAR GOBIND KHORANA
 synthesising RNA molecules with defined combinations of
bases (homopolymers and copolymers).
 interpretation of the genetic code and its function in protein
synthesis.
 Building of different RNA chains with the help of enzymes.
Using these enzymes, he was able to produce proteins.

5. MARSHALL WARREN NIRENBERG
 discovered the first "triplet"—a sequence of three
bases of DNA that codes for one of the twenty
amino acids that serve as the building blocks of
proteins.

6. SEVERO OCHOA
 Discover enzyme polynucleotide phosphorylase
 mechanisms in the biological synthesis of ribonucleic
acid and deoxyribonucleic acid".

7. CODONS
 Sequence of nitrogenous bases on m RNA
 Triplet of base is known as Codons
 The codons are written 5' to 3', as they appear in
the mRNA.

8. NITROGEN BASES IN RNA
U, C, A, G

10. SALIENT FEATURES OF GENETIC CODE
The codon is triplet.
61 codons code for amino acids and 3 codons do not code for any amino
acids, hence they function as stop codons.
Some amino acids are coded by more than one codon, hence the code is
degenerate.
The codon is read in mRNA in a contiguous fashion. There are no
punctuations.
The code is nearly universal: for example, from bacteria to human
AUG has dual functions. It codes for Methionine (met) , and it also act as
initiator codon.
UAA, UAG, UGA are stop terminator codons.

11. CODON IS TRIPLET

12. CODON IS DEGENERATE
 Some amino acids are coded by more than one codon.

13. UNAMBIGOUS
 ONE CODON CODES FOR ONLY ONE AMINO
ACID
 EX- AUG always codes for Methionine

14.  EXCEPTIONS
GENETIC CODE IS UNIVERSAL- EXCEPTIONS

15. NO PUNCTUATIONS
 The codon is read in mRNA in a contiguous fashion.
There are no punctuations.

16. AUG
 AUG has dual functions.
 It codes for Methionine (met)
 also act as initiator codon.

17. STOP CODONS
 UAA (OCHRE)
 UAG (AMBER)
 UGA (OPAL)

18. CODAN VS ANTICODON
 Codon – on mRNA
 Anticodon- on t RNA

19. THANK YOU