DNA RNA

1. 1

2. NUCLEIC ACIDS:
•Arebiologicalmoleculesessentialforknownformsoflife
onearth
•TheyincludeDNAandRNA
•DiscoveredbyFriedrichMiescherin1869
•Theyarenamedsobecauseoftheirinitialdiscoveryin
nucleus

3. DNAstands for deoxyribo nucleic acid
This chemical substance is present in the nucleus
of all cells in all living organisms
DNA controls all the chemical changes which
take place in cells
The kind of cell which is formed, (muscle, blood,
nerve etc) is controlled by DNA
The kind of organism which is produced (buttercup,
giraffe, herring, human etc) is controlled by DNA
DNA 2

4. DNAis a very large molecule made up of a long
chain of sub-units
The sub-units are called nucleotides
Each nucleotide is made up of
a sugar called deoxyribose
a phosphate group -PO
4 and
an organic base
DNA molecule 3

5. The deoxyribose, the phosphateand one of the bases
adenine
deoxyribose
PO
4
Combine to form a nucleotide
NUCLEOTIDES
6

6. The most common organic bases are
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
THE BASES
5

7. The bases always pair up in the same way
Adenine forms a bond with Thymine
and Cytosine bonds with Guanine
Bonding 1 10
Adenine Thymine
Cytosine
Guanine

8. •Adenineandguanineareknownas
PURINES
•Thymineandcytosineareknownas
PYRIMIDINES,inRNAinsteadofthymine
itisUracil
•AdeninepairswithThymineformingtwo
hydrogenbonds
•CytosinepairswithGuanineformingwith
threehydrogenbonds

9. Purines Pyrimidines
Purinesare double ringed structuresPyrimidinesare single ringed
structures
Example of purinebases are
Adenine and Guanine
Example of pyrimidinebases are
Thymine and Cytosine( in DNA),
Uraciland cytosine ( in RNA)

10. Riboseis a sugar, like glucose, but with only five
carbon atoms in its molecule
Deoxyriboseis almost the same but lacks one
oxygen atom
Both molecules may be represented by the symbol
THE SUGARS:RIBOSE & DEOXYRIBOSE
4

11. STRUCTURE OF DEOXYRIBONUCLEOTIDE
AND RIBONUCLEOTIDE

12. NUCLEOSIDE NUCLEOTIDE
Nucleoside is a component formed by
the union of a nitrogen base with a
pentose sugar
Nucleotideisacomponentformed
bytheunionofanitrogenbase,a
pentosesugarandphosphate
It is a component ofnucleotide It formedafter phosphorylation of
nucleoside

13. FUNCTIONS OF DNA:
•Itisthegeneticmaterial,thereforeresponsibleforcarrying
allthehereditaryinformation.
•Ithaspropertyofreplicationessentialforpassinggenetic
informationfromonecelltoitsdaughtersorfromone
generationtonext.
•Crossingoverproducesrecombination
•Changesinsequenceandno.ofnucleotidescauses
Mutationwhichisresponsibleforallvariationsand
formationofnewspecies.
•ItcontrolsallthemetabolicreactionofcellsthroughRNAs
andRNAdirectedsynthesisofproteins.

14. A molecule of
DNA is formed
by millions of
nucleotides
joined together
in a long chain
PO
4
PO
4
PO
4
PO
4
sugar-phosphate
backbone
+ bases
Joined nucleotides 7

15. In fact, the DNA usually consists of a double
strand of nucleotides
The sugar-phosphate chains are on the outside
and the strands are held together by chemical
bonds between the bases
8

16. PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
2-stranded DNA
9

17. PO
4
PO
4
PO
4
thymine
PO
4
PO
4
PO
4
PO
4
adenine
cytosine
PO
4
guanine
Bonding 2 11

18. PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
PO
4
Pairing up 12

19. ROLE OF PHOSPHODIESTER
LINKAGE
•PhosphodiesterBonds Link
SuccessiveNucleotidesinNucleic
Acids
•Thesuccessivenucleotidesofboth
DNAandRNAarecovalently
linkedthroughphosphate-group
“bridges,”inwhichthe5’-
phosphategroupofonenucleotide
unitisjoinedtothe3-hydroxyl
groupofthenextnucleotide,
creatingaphosphodiesterlinkage.

20. Thechainhasa5end,
whichisusuallyattached
toaphosphate,anda3
end,whichisusuallya
freehydroxylgroup

21. The paired strands are coiled into a spiral called
A DOUBLE HELIX
13

22. sugar-phosphate
chain
bases
THE DOUBLE
HELIX
14

23. ANTIPARALLEL NATURE
•ThetwostrandsofDNAarealsoantiparallel(run
inoppositedirections)tooneanother.
•AstrandofDNAcanhavethedirection5'-3'or3'-
5'.
•OnestrandintheDNAmoleculeis5'-3'andthe
otherstrandis3'-5'.

24. DNA STRUCTURE

25. •Thetwostrandsrunantiparallelyandarecomplimentarytoeach
other.
•Thecoilingisrighthanded.
•Themajorgrooveoccurswherethebackbonesarefarapart,the
minorgrooveoccurswheretheyareclosetogether.
•Twohelicalpolynucleotidechainsarecoiledaroundacommon
axis.Thechainsruninoppositedirections.
•Thesugar-phosphatebackbonesareontheoutsideand,therefore,
thepurineandpyrimidinebaseslieontheinsideofthe
helix.AdeninealwayspairswithThymine,Guaninebindswith
Cytosine
•Thebasesarenearlyperpendiculartothehelixaxis,andadjacent
basesareseparatedby3.4Å.
•Thehelicalstructurerepeatsevery34Å,sothereare10bases(=34
Åperrepeat/3.4Åperbase)perturnofhelix.
•Thereisarotationof36degreesperbase(360degreesperfull
turn/10basesperturn).
•Thediameterofthehelixis20Å.

27. CHARGAFFS RULE:
•“ItstatesthatDNAfromanycellofallorganismsshould
havea1:1ratioofpyrimidineandpurinebasesandmore
specificallythattheamountofguanineisequaltoamount
ofcytosineandamountofadenineisequaltoamountof
thymine”
•%A=%T
•%G=%C

28. DENATURATION OR MELTING
•Thehydrogenbondsbetweenthenitrogenousbasesof
complementrayDNAcanbreakduetohightemperature,
loworhighpHknownasMeltingorDenaturationof
DNA.
•A-Tbasepairscangoeasydenaturationduetopresence
ofonlytwohydrogenbonds,whereasG-Cbasepairsare
comparitivelymorestable(highmeltingpoint)dueto
presenceofthreehydrogenbonds.

29. RNA
•LikeDNA,RNAisalsomadeofalongchainof
nucleotides.
•SomeRNAmoleculesplayanactiveroleincellsby
catalyzingbiologicalreactions,controllinggene
expression,orsensingandcommunicatingresponsesto
cellularsignals.
•InRNAmoleculesinsteadofthebaseT,baseUisfound.
•GenerallythreetypesofRNAmoleculesarefoundinthe
cell–mRNA,rRNA,andtRNA.

30. MESSENGER RNA:mRNA
•Compriseonly5%oftotalcellularRNA.
•MessengerRNA(mRNA)carriesinformationaboutaprotein
sequencetotheribosomes,theproteinsynthesisfactoriesin
thecell.
•Itiscodedsothateverythreenucleotides(acodon)
correspondtooneaminoacid.
•ThesynthesisofmRNAtakesplaceinsidethenucleusand
afteritssynthesis,itisexportedoutwhereitattachesto
ribosomesforproteinsynthesis.
•AftercertainamountoftimethemessageinmRNAis
degradedintoitscomponentnucleotides.

31. TRANSFER RNA:tRNA
•tRNArepresents15%oftotalRNAinthecell.
•TransferRNA(tRNA)isasmallRNAchainofabout80
nucleotidesthattransfersaspecificaminoacidtoagrowing
polypeptidechainattheribosomalsiteofproteinsynthesis
duringtranslation.
•Ithassitesforaminoacidattachmentandananticodonregion
forcodonrecognitionthatbindstoaspecificsequenceonthe
messengerRNAchainthroughhydrogenbonding.

32. STRUCTURE OF tRNA
•Anticodonarm:
•Madeupofthreenitrogenbasesfor
recognisingandattachingtothe
codonofmRNA
•A-ABindingSite:
Itliesatthe3’endandhasCCA-OH
group
•TΨCLoop:
Containspseudouridine,sitefor
attachingtheribosomes
•DHULoop:
Containsdihydrouridine,bindingsite
foraminoacylsynthetaseenzyme.
•Variableloop:
LiesbetweentheanticodonandTΨC
loop.

34. RIBOSOMAL RNA (rRNA):
•80%oftotalRNAinthecellsarerRNA
•RibosomalRNAisaconstituentof
Ribosomes
•rRNAarefoundincombinationwith
severalproteins(about82proteins)as
componentoftheribosomewhichisthesite
ofproteinsynthesis.

35. CENTRAL DOGMA
•The set of ideas that describes how the cell uses the information
stored in DNA is called the Central dogma
•The first step of central dogma is Transcription
•Transcription uses DNA as a template to copy genetic information
into form of RNA
•The second step of central dogma is Translation
•Translation synthesizes the protein using RNA as a template

36. Character RNA DNA
Nitrogenous bases RNA contains adenine,
uracil, cytosine, and
guanine.
DNA contain adenine,
thymine, cytosine,
guanine;
Strandedness RNA is single-stranded. DNA is double-stranded
Location RNA can be found in both
the nucleus and
cytoplasm.
DNA is only found in the
nucleus
Functions RNA carries out protein
synthesis.
RNA transfers the
information to other
places in the cell
DNA contains the
information for protein
synthesis.
DNA stores genetic
information
Pentose sugar Hydroxyl group present at
2 carbon of the pentose
sugar
Absence of hydroxyl
group at 2 C of the
pentose sugar