Degeneracy in genetic code

Degeneracy in genetic code

1. POWERPOINT PRESENTATION BY: SNEHA SUSAN MATHEW (15MSI0065) DEGENERACY IN GENETIC CODE

2. CENTRAL DOGMA

3. TRANSLATION THE PATHWAY OF PROTEIN SYNTHESIS IS CALLED TRANSLATION BECAUSE THE LANGUAGE OF NUCLEOTIDE SEQUENCE ON mRNA IS TRANSLATED IN TO THE LANGUAGE OF AMINO ACID SEQUENCE. THE PROCESS OF TRANSLATION REQUIRES A GENETIC CODE , THROUGH WHICH THE INFO CONTAINED IN THE NUCLEIC ACID SEQUENCE IS EXPRESSED TO PRODUCE A SPECIFIC SEQUENCE OF AMINO ACID .

4. GENETIC CODE SET OF RULES BY WHICH INFORMATION ENCODED WITHIN GENETIC MATERIAL IS TRANSLATED INTO PROTEINS. TERM GIVEN BY GEORGE GAMOW .

5. SALIENT FEATURES OF GENETIC CODE

6. TRIPLET CODON THREE ADJACENT NITROGEN BASES CONSTITUTE A CODON WHICH SPECIFIES THE PLACEMENT OF ONE AMINO ACID IN A POLYPEPTIDE. 1 CODON = 1 AMINO ACID

7. UNAMBIGUOUS AND SPECIFIC ONE CODON CODES FOR ONLY ONE AMINO ACID. EXAMPLE: AUG CODES FOR METHIONINE.

8. UNIVERSAL THE CODE IS NEARLY UNIVERSAL. AUG – METHIONINE AUG -- VALINE FOR EXAMPLE: FROM BACTERIA TO HUMANS UUU WOULD CODE FOR PHENYLALANINE ( phe ).

9. COMMALESS THE GENETIC CODE IS CONTINOUS AND DOES NOT POSSESS PAUSES AFTER THE TRIPLETS. IF A NUCLEOTIDE IS ADDED OR DELETED, THE WHOLE GENETIC CODE WILL READ DIFFERENTLY .

10. THERE ARE 64 POSSIBLE COMBINATIONS OF 3 LETTER NUCLEOTIDE SEQUENCES . 61 REPRESENTS AMINO ACIDS AND 3 ARE STOP CODONS. NIRENBERG AND HAR GOBIND KHORANA PREPARED THE GENETIC CODON TABLE FOR VARIOUS AMINO ACID.

11. CODON TABLE

12. DEGENERACY OR REDUNDANCY IN GENETIC CODE SOME AMINO ACIDS MAY BE INFLUENCED BY MORE THAN ONE CODON. AMINO ACIDS ARE SPECIFIED BY TWO TO SIX CODONS. EXAMPLE: phe – UUU, UUC Arginine- CGU,CGC,CGA,AGA,AGG. DEGENERACY RESULTS THERE ARE MORE CODONS TO ENCODE 20 AMINO ACIDS.

13. DEGENERACY GUU = VALINE GUA = VALINE GUC = VALINE GUG = VALINE

14. UU U : XY U UU C : XY C UU A : XY A UU G : XY G

15. IN DEGENERATE CODONS,GENERALLY THE FIRST TWO NITROGEN BASES ARE SIMILAR WHILE THE THIRD ONE IS DIFFERENT.

16. WOBBLE HYPOTHESIS ACCORDING TO THIS HYPOTHESIS, ONLY THE FIRST TWO BASES OF THE CODON HAVE A PRECISE PAIRING WITH THE BASES OF THE ANTICODON OF mRNA WHILE THE PAIRING BETWEEN THE THIRD BASES OF CODON AND ANTICODON MAY WOBBLE(NON-SPECIFIC).

17. Nucleotide at 5' end of anticodon Nucleotide at 3' end of anticodon G U or C C G A U U A or G I (indosine) A, U or C

18. MUTATION ANY CHANGE IN THE IN THE GENETIC CODE CAUSES MUTATION .

19. FRAME SHIFT MUTATION AUG GUG A G C AGG ADDITION AUG GUG A C G CAG G

20. THANKYOU