The genetic code consists of rules that translate DNA or RNA sequences into protein sequences via codons, which are triplets of nucleotides. Key contributors like George Gamow, Har Gobind Khorana, Marshall Nirenberg, and Severo Ochoa advanced understanding of codons and their roles in protein synthesis, highlighting features such as the code's universality and degeneracy. The document explains the roles of codons and anticodons in this process, including details about start and stop codons.

1. Dr Rama Kant Upadhyay
GENETIC CODE

2. GENETIC CODE
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.
George Gamow
To code for all the 20 amino acids, the code should be made up of
three nucleotides Codon is triplet
4 3 = 64 codons
Har Gobind Khorana
• Syntheses 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.
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.

3. Severo Ochoa
Discover enzyme polynucleotide phosphorylase mechanisms in the biological
synthesis of ribonucleic acid and deoxyribonucleic acid".

4. Codons
 Sequence of nitrogenous bases on m RNA Triplet of the base is known as Codons
 The codons are written 5' to 3', as they appear in the mRNA.
 A codon is a group of three bases in messenger RNA (mRNA) that specifies a
particular amino acid.
codons

5. Anticodons
Anticodons are three-nucleotide sequences in transfer RNA (tRNA) molecules that
pair with complementary codons in messenger RNA (mRNA) during protein synthesis.
Anticodons
Codons

6. U, C, A, G
Nitrogen bases in RNA

7. https://ib.bioninja.com.au/genetic-code/

8. 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.
salient features of genetic code

9. • One codon codes for only one amino acid
• EX- AUG always codes for Methionine
unambigous
Degenerate
• Some amino acids are coded by more than one codon
No punctuations/ Comma less
• 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 UUU would code
for Phenylalanine (phe).
• Some exceptions to this rule have been found in mitochondrial codons, and in some
protozoans.
Universal

10. GENETIC CODE IS UNIVERSAL- EXCEPTIONS

11. • It codes for Methionine (met)
• also act as initiator codon.
• Synthesis of polypeptide starts with AUG (Methionone)
AUG
STOP CODON
• UAA (OCHRE)
• UAG (AMBER)
• UGA (OPAL)
• Translation process stops with any of the stop
codons.
https://www.genome.gov/genetics-glossary/Stop-Codon

12. THANK YOU
Source: NCERT Text book, google images