presentation for nucleic acids

1. NUCLEIC ACIDS
All Regards to my teacher.

2. PRESENTED BY
(GROUP 4)
1. MuhammmadTahir
2. Ali zia
3. Hafiz MuhammadArshad

3. Brief History
■ 1869 - Miescher – Isolated nuclein from soiled bandages
■ 1902 - Garrod – Studied rare genetic disorder: Alkaptonuria; concluded that specific
gene is associated with absence of a specific enzyme.
■ 1903 - Sutton – Chromosome structure
■ 1913 - Morgan – Gene mapping
■ 1926 - Sumner – Purified Urease; identified enzyme to be proteins
■ 1928 - Griffith –Transforming Principle – a chemical transferred from dead bacteria to
living cells caused genetically converted strains (“transformation”)
■ 1944 - Avery, McCarty, and Macleod – Identified Griffith’s “transformation principle” as
DNA
■ 1947 - Chargaff – Base pairing
■ 1950’s - Franklin – X-ray of DNA
■ 1953 -Watson and Crick – DNA double helix

4. Introduction
■ Nucleic acids are polymers that consist of nucleotide residues.
■ They are the macromolecules present in most living cells either in the free stateor bound to
proteins as nucleoproteins.
■ Like the proteins, the nucleic acids are biopolymers of high molecular weight with
mononucleotide as their repeating units, just as amino acids are the repeating units of proteins.
■ As regards their elemental composition, the nucleic acids contain carbon, hydrogen, oxygen,
nitrogen and, strangely enough, phosphorus ; the percentage of the last two elements being
about 15 and 10, respectively.

5. Structure of nucleotide
Each nucleotide is put together from three
building blocks:
1) phosphoric acid
2) a monosaccharide
3) an organic base

6. 1) Phosphoric Acid

7. 2) Monosaccharides
All nucleotides are constructed from one of these two monosaccharides:

8. 3.Organic Bases
There are two types of organic bases (amines) that are incorporated into nucleic acids:
1. Purines
2. pyrimidines

9. 1.Purines

10. 2.Pyrimidines

11. Tautomerism in nitrogenous bases
■ Compounds that exist in 2 structural isomeric forms which are mutually
interconvertible and exist in dynamic equilibrium are called tautomers and the
phenomenon is termed tautomerism.

12. Examples of tautomerism in nitrogenous
bases

13. Nucleosides
■ When ribose or 2-deoxyribose is combined with a purine or pyrimidine base, a nucleoside is
formed.
■ Nucleosides containing ribose are called ribonucleosides.

14. Nucleosides
■ Nucleosides containing 2-deoxyribose are called deoxyribonucleosides.

15. Nucleosides

16. Nucleotides
•When phosphate ion is bonded
with one of the -OH groups on the
sugar residue of a nucleoside to
form a phosphate monoester, a
nucleotide is produced.
•In a nucleotide, the sugar and
phosphate residues are connected
by a phosphoester bond.
•In a nucleotide, the sugar and
organic base residues are
connected by a N-glycosidic bond.

17. Nucleotides
■ The phosphate ion can bond with 3’ carbon on the sugar residue of a nucleoside to form a
3’nucleotide.

18. Nucleotides
■ More common in nature, the phosphate ion can bond with the 5’ carbon on the sugar
residue of a nucleoside to form a 5’nucleotide.

19. Nucleotides
■ Ribonucleosides form ribonucleotides
■ Deoxyribonucleosides form deoxyribonucleotides.

20. NUCLEOTIDE STRUCTURE
PHOSPHATE SUGAR
Ribose or
Deoxyribose
NUCLEOTIDE
BASE
PURINES PYRIMIDINES
Adenine (A)
Guanine(G)
Cytocine (C)
Thymine (T)
Uracil (U)

21. Deoxyribonucleic acid
■ DeoxyribonucleicAcid – polymer of nucleic acids (polynucleotide)
■ Functions as storage for genetic information.
■ DNA polymerase is used to catalyze the synthesis of DNA. Synthesis occurs in the 5’to
3’ direction.

22. Deoxyribonucleic acid
■ Each strand of the double helix is orientated in the opposite direction.
■ DNA is acidic due to the phosphate groups between each 2’deoxyribose.
■ ContainsAdenine, Guanine,Cytosine, andThymine
■ Primary structure: nucleic acid sequence; Secondary structure: double helix;Tertiary
structure:nucleic acids supercoil and wrap around histones (proteins)
■ In eukaryotic cells (plants, animals, fungi, & protists), DNA is located in the cell
nucleus.
■ In prokaryotic cells (eubacteria & archaea), DNA is located in the nucleoid; there is no
nuclear envelope to separate DNA from the cytoplasm.

23. A short strand of DNA containing six
nucleotides

24. THE SUGAR-PHOSPHATE
BACKBONE
■ The nucleotides are all
orientated in the same
direction
■ The phosphate group joins
the 3rd Carbon of one sugar to
the 5th Carbon of the next in
line.
P
P
P
P
P
P

25. DNA IS MADE OFTWO
STRANDS OF
POLYNUCLEOTIDE
P
P
P
P
P
P
C
G
G
T
A
A
P
P
P
P
P
P
G
C
C
A
T
T
Hydrogen bonds

26. Watson & Crick Base pairing
© 2016 Paul Billiet ODWS

27. Ribonucleic acid
■ RibonucleicAcid – polymer of nucleic acids (polynucleotide)
■ Functions as template for translating genes into proteins, transfers amino acids to the
ribosome site on a growing polypeptide chain, etc.
■ Unlike DNA, RNA is single-stranded and consists of a shorter nucleotide chain
■ Hydroxyl group on the ribose causes RNA to be less stable than DNA because it is
easier to undergo hydrolysis.
■ ContainsAdenine, Guanine,Cytosine, and Uracil

28. A strand of RNA

29. Types of RNA
■ mRNA – Messenger RNA; brings information from DNA to ribosome sites for protein
synthesis.
■ tRNA –Transfer RNA; transfers a specific amino acid to a polypeptide chain during the
translation phase of protein synthesis.
■ Ribosomal RNAs (rRNA) are relatively long RNA strands (hundreds or thousands of
nucleotide residues) that combine with proteins to form ribosomes, the multisubunit
complexes in which protein synthesis takes place.

30. Chargaff’s Rules
■ A pairs withT (ratio 1:1); G pairs
with C (ratio 1:1)
Note: Ratios are random in RNA

31. Stability of DNA
Aromatic Stacking
■ Weak noncovalent force caused by overlapping of p-orbitals; also called pi stacking. In
DNA, aromatic stacking between the nucleotides contributes to its stability.The
pyrimidine and purine bases, which are parallel to each other in DNA, participate in
aromatic stacking due to the overlap of their p-orbitals.
Hydrogen Bonding
■ Millions of hydrogen bonds in DNA is the main structural feature that explains why
DNA is stable. Hydrogen bonding is strong, but can easily be broken for DNA
replication.

32. Nucleic acid and protein production
The following three processes are involved in duplication, transfer, and use of genetic
information:
■ Replication
■ Transcription
■ Translation

33. 1.Replication
The process by which a replica, or identical copy, of DNA is made when a cell divides.

34. Replication
• When DNA is replicated, each strand of the
double helix serves as a template for the
manufacture of a new strand of DNA.
• In each of the daughter DNA strands, one
strand from the parent DNA is present.
•This is called semiconservative replication.

35. Detailed DNA Replication Illustration

36. 2.Transcription
■ The first step in using the information stored in DNA to produce proteins is
Transcription; using DNA as a template to make RNA.

37. Transcription of DNA to produce mRNA

38. 3.Translation
■ The synthesis of proteins occur at ribosomes, which are outside the nucleus and within
the cytoplasm of cells.
■ The mRNA connects with the ribosome, and the amino acids attached to transfer RNA
(tRNA) are delivered one by one.

39. Protein synthesis, or translation,
takes place in three steps:
■ Initiation
■ Elongation
■ Termination

40. 1. Initiation
A ribosome, mRNA, and tRNA come together to form a complex.

41. 2.Elongation
Amino acids are joined to the growing polypeptide chain.

42. 3.Termination
The protein has been synthesized and the ribosome-mRNA-tRNA complex dissociates.

43. Control of Gene
Expression
■ The DNA of each living thing contains thousands of genes.
■ These genes are not continually expressed(read to make proteins), because the
production of unneeded proteins would be an inefficient use of resources.
■ Control of gene expression prevents the manufacture of unwanted/unneeded
proteins.

44. Example: Control of the lac operon

45. Mutation
■ Any permanent change in the primary structure of (sequence of nucleotide residues in) DNA is
called a mutation.
■ Mutations might involve the switching of one base pair for another or the addition or deletion
of base pairs.
■ Errors in replication and exposure to mutagens (mutation-causing agents, including x rays, UV
radiation, nuclear radiation, and chemicals) are the common causes of Mutations.
■ When the mutations are in the sex cells (sperm or ovarian cells), the mutation can be inherited -
genetic diseases.

46. Comparison between DNA and RNA
DNA RNA
■ Most of RNA (90%) is present in the
cell cytoplasm and a little (10%) in
the nucleolus.
■ May be present in free state.
■ The sequence of an RNA molecule is
the same as that of the ‘antisense’
strand.
■ RNA is stained red with pyronin.
■ Found mainly in the chromatin of the
cell nucleus.
■ Never present in free state in
cytoplasm.
■ DNA has both ‘sense’ and
‘antisense’ strands.
■ DNA is stained green with a dye,
pyronin.

47. Comparison between DNA and RNA
DNA
■ Normally double-stranded and rarely
single-stranded.
■ Sugar in DNA is 2′-
deoxyribose(hence the
nomenclature) which contains an H
atom at C-2.
■ The common nitrogenous bases are
adenine,guanine, cytosine and
thymine (but not uracil).
RNA
■ Normally single-stranded and rarely
double-stranded.
■ Sugar in RNA is ribose (hence the
nomenclature) which contains a 2′-
hydroxyl group.
■ The common nitrogenous bases are
adenine,guanine, cytosine and uracil
(but not thymine).

48. Comparison between DNA and RNA
DNA
■ Base pairing is inevitable during which adenine pairs with thymine
and guanine with cytosine.
■ DNA acts as a template for its synthesis.
■ DNA on replication forms DNA and on transcription forms RNA.
RNA
■ In case pairing takes place, adenine pairs
with uracil and guanine with cytosine.
■ RNA does not act as a template for its
synthesis.
■ Usually RNA does not replicate or
transcribe.

49. Thanks for listening