The document discusses genetic code, mutations, tRNA, and the translation process. Some key points: - The genetic code specifies how nucleic acids correspond to amino acids in proteins. It is nearly universal but has some exceptions. - Mutations like point mutations and frameshift mutations can alter the genetic code sequence. A point mutation in sickle cell anemia changes one nucleotide, altering the amino acid produced. - tRNA acts as an adapter between mRNA and amino acids. It has an anticodon loop that binds to mRNA codons and an amino acid binding end. - Translation involves initiation, elongation, and termination on the ribosome. Charged tRNAs bring amino acids and bind mRNA cod

1. Genetic code
&
Mutations:
t-RNA
&
Translation process

2. GENETIC CODE
• The change in nucleic acids (genetic material) were
responsible for change in amino acids in proteins.
• the proposition and deciphering of genetic code were
most challenging. identifying (something).

4. GENETIC CODE
• The process of translation requires transfer of genetic
information.. M-RNA to Proteins,,,
•
• Neither does any complementarity exist between
nucleotides and amino acids…

5. GENETIC CODE
• The change in nucleic acids (genetic material) were
responsible for change in amino acids in proteins.
• The proposition and deciphering of genetic code were
most challenging. identifying (something).

6. • To understanding of genetic code require involvement of
scientists from several disciplines –
• physicists,
• organic chemists,
• biochemists
• geneticists

7. George Gamow
• He argued that since there are only 4 bases and if they
have to code for 20 amino acids.
• In order to code for all the 20 amino acids, the code
should be made up of three nucleotides.
• Combination of 43 (4 × 4 × 4) would generate 64
codons.

8. Har Gobind Khorana..
• He developed chemical method for instrumental
synthesis of RNA molecules..
• with defined combinations of bases (homopolymers
and copolymers).

9. Father of genetic code…(Nobel prize in 1968)?
• Marshall Nirenberg’s cell-free system for protein
synthesis..
• Finally helped the code to be deciphered..
• .

10. • Severo Ochoa: Severo Ochoa enzyme (polynucleotide
phosphorylase).
• He developed enzymatic method for RNA synthesis.

11. The salient features of genetic code:
• (i) The codon is triplet. Total 64 codons.
• There are 61 codons code for amino acids..
• 3 codons do not code for any amino acids, they
function as stop codons.

13. • (ii) One codon codes for only one amino acid, hence, it is
unambiguous and specific.
ALANINE

14. • (iii) Some amino acids are coded by more than
one codon, hence the code is degenerate.

15. • (iii) Some amino acids are coded by more than one
codon, hence the code is degenerate.
• Tryptophan (UGG)
• Methionine (UAG)
• Phenylalanine (UUU,UUC)
• Aspartic acid (GAU, GAC)
• Glutamic acid (GAA, GAG)
• Lysine (AAA, AAG)
• Tyrosine (UAU, UAC)
No of codon each
amino acid is: 2
No of codon each amino acid is: 1

16. • Isoleucine (AUU, AUC, AUA)
• Valine
• Proline
• Threonine
• Alanine
• Glycine
• Leucine,
• Arginine
• Serine
No.of codon each amino acid
is: 3
No.of codon each amino acid is: 4
No of codon each amino acid is: 6

17. • (iv) The codon is read in mRNA in a contiguous fashion.
There are no punctuations.

18. • (v) 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.
• .

19. • (vi) AUG has dual functions. It codes for Methionine
(met) , and it also act as initiator codon.

20. The genetic code is non overlapping,
i.e.,the adjacent codons do not
overlap

21. • (i) 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.
• (ii) One codon codes for only one amino acid, hence, it is unambiguous and
specific.
• (iii) Some amino acids are coded by more than one codon, hence the code is
degenerate.
• (iv) The codon is read in mRNA in a contiguous fashion. There are no
punctuations.
• (v) The code is nearly universal: for example, from bacteria to human. Some
exceptions to this rule have been found in mitochondrial codons, and in some
protozoans.
• (vi) AUG has dual functions. It codes for Methionine (met) , and it also act as
initiator codon.

22. Gln:
Glutamine
ASN:
Asparagine
ASP: Aspartic
acid,
Glu: Glutamic
acid
Cys: cysteine

24. • A mutation is a change that occurs in DNA
sequence.
• The term mutation coined by: Hugo devries.

25. Point mutations and Frame shift mutations
• Point mutations happen when there is a
replacement of one base pair from another.

26. Point mutations:
• Point Mutations: arise due to changes in single
base pair in DNA.
Example: Sickle cell anemia;

27. Sickle cell anemia;
• Single base substitution at sixth codon of beta
globin gene form GAG (Glutamic acid) to GUG
(Valine).

28. Sickle cell anemia

29. • Frameshift mutations: occur when there is
an insertion or deletion of the base pairs from the
DNA sequence.
• Frame shift mutations: 1).insertion 2).Deletion..

30. Frame shift insertion mutations
• RAM HAS RED CAP
• RAM HAS BRE DCA P
• RAM HAS BIR EDC AP
• RAM HAS BIG RED CAP.

31. Frame shift insertion mutations
• Insertion of one or two bases changes the reading
frame from the point of insertion..
• Insertion of three or its multiple bases (OR) one or
multiple codons reading frame remains unaltered from
that point of insertion.

32. Frame shift Deletion mutations
• RAM HAS RED CAP
• RAM HAS EDC AP
• RAM HAS DCA P
• RAM HAS CAP

33. Frame shift Deletion mutations
• Deletion of one or two bases changes the reading
frame from the point of Deletion..
• Deletion of three or its multiple bases (OR) one or
multiple codons reading frame remains unaltered from
that point of Deletion.

35. • r-RNA : 80%
• t-RNA: 10-15%
• m-RNA: 1-2%

36. t-RNA or Adaptor

37. tRNA– the Adapter Molecule
Dihydrouridine
loop..
It is binding
site of amino
acyl t-RNA
synthetase
enzyme
Pseudouridine
loop
involved in
binding of
ribosomes
Dihydrouridine loop..
Pseudouridine loop

38. • Francis Crick postulated the presence of an adapter
molecule.
• t-RNA on one hand read the code and on other hand
would bind to specific amino acids.

39. • tRNA has an anticodon loop that has bases
complementary to the codon of m-RNA.
• t-RNA has an amino acid acceptor end to which it binds
to amino acids.

40. • The tRNA, then called sRNA (soluble RNA).
• tRNA is also called soluble RNA because it is soluble in
1M (molar) NaCl.
• For initiation of translation, there is another specific
tRNA that is referred to as initiator tRNA.
• There are no tRNAs for stop codons.

41. • The secondary structure of tRNA has been depicted that
looks like a clover -leaf.
• In actual structure (Tertiarty) the tRNA is a compact
molecule which looks like inverted L.

42. Translation

43. Translation
• Translation refers to the process of polymerisation of
amino acids to form a polypeptide..
• The order and sequence of amino acids are defined by
the sequence of bases in the mRNA…

44. Translation
• The amino acids are joined by a bond which is known as
a peptide bond.
• Formation of a peptide bond requires energy.

45. Translation
• The first phase itself amino acids are activated in the
presence of ATP.
• Activated amino acids linked to their cognate tRNA .
• This process commonly called as charging of tRNA or
amino-acylation of tRNA.
(related)
UAC

46. Translation
• Initiation
• Elongation
• Termination

47. Initiation
• The cellular factory responsible for synthesising
proteins is the ribosome.
• The ribosome consists of structural RNAs and about 80
different proteins.

48. Initiation
• When the small subunit (30s) binds to mRNA, at start
codon the process of translation of the mRNA to
protein begins.

49. • For initiation, the ribosome binds to the mRNA at the
start codon (AUG)…
• and followed by the base pairing of AUG with the
initiator tRNA.

50. Initiation

51. • Elongation:
• The ribosome proceeds to the elongation phase of
protein synthesis.
• During these phase charged-tRNAs, bind to the
appropriate codon in mRNA by forming
complementary base pairs with the tRNA anticodon.

52. Elongation:
• There are two sites in the large subunit,..
• The charged amino acids close enough to each other
the peptide bond formed between them.

53. Elongation:
• The ribosome also acts as a catalyst (23S rRNA in
bacteria is the enzyme- ribozyme) for the formation
of peptide bond.
• 23S rRNA present in 50s subunit of prokaryotes.

54. Elongation:

55. Termination
• The ribosome moves from codon to codon along the
mRNA.
• Amino acids are added one by one, translated into
Polypeptide sequences dictated by DNA and represented
by mRNA.

56. Termination
• At the end, a release factor binds to the stop codon,
terminating translation and releasing the complete
polypeptide from the ribosome.

57. Untranslated regions (UTR).
The UTRs are present at both 5' -end (before start codon) and at 3'
-end (after stop codon).
They are required for efficient translation process.

58. UTR
• A translational unit in mRNA is the sequence of RNA
that is flanked by the start codon (AUG) and the stop
codon and codes for a polypeptide.
• An mRNA also has some additional sequences that
are not translated and are referred as untranslated
regions (UTR).

59. • In prokaryotes the initiator t-RNA is tRNAfmet.
• The methionine is formulated.
• Two site in large subunit of ribosome
• A site (Amino acyl site)
• P site (Peptidyl site)

60. Peptidyl transferase
• Peptide bond formation between amino acid
during translation catalysed by Peptidyl
transferase.
• 23SrRNA and 28SrRNA perform this function
therefore they act as Ribozyme.

62. • What would happen if in a gene encoding a polypeptide of
50 amino acids, 25th codon (UAU) is mutated to UAA?
• 1) A polypeptide of 24 amino acids will be formed.

63. Regulation of gene expression
• Regulation of gene expression occur at various levels.
• Gene expression results in the formation of a
polypeptide…

64. In eukaryotes, the Gene regulated at
• (i) transcriptional level (formation of primary transcript).
• (ii) processing level (regulation of splicing),
• (iii) transport of mRNA from nucleus to the cytoplasm.
• (iv) translational level.

65. • The metabolic, physiological or environmental
conditions that regulate the expression of genes.

66. • The development and differentiation of embryo into
adult organisms are…..
• also a result of the coordinated regulation of expression
of several sets of genes

68. Dr. HarinathaReddy Aswartha
Assistant professor
Department of Microbiology
ANDHRAPRADESH
INDIA