Nucleic acids are the basic informational supermolecules that contributes to the most indispensable characteristic belongingss of life system, reproduction and familial conttrols. Lower and higher molecular weight of nucleic acids are utilized in metabolic and catalytic reactions severally.
Deoxyribonucleic acid ( deoxyribonucleic acid ) and RNA ( ribonucleic acid ) are nucleic acid of polymers composed of nitrogen-bearing base either a dual ring of purines and individual ring of pyrimidine which is further connected to the phosphorylated sugar to do up the nucleotides.The sugar attached with base without phosphate group is called nucleoside.The DNA molecule has sugar 2′-deoxyribose and RNA molecule has ribose and every anchor of DNA or RNA concatenation are linked by covalent phosphodiester bond between 5’and 3’carbons of two sugars either from 5 ‘ — – & A ; gt ; 3 ‘ or 3 ‘ — – & A ; gt ; 5 ‘ waies.
Phosphate groups are attached at the terminal of the sugar at 5′-carbon and at the 3’end, the hydroxyl group is added.Most likely all natural DNA or RNA polymer extend in a way of 5’to 3’end direction.The constructions that join the nulceotides together in DNA and RNA are called phosphodiester bonds due the presence of phosphorous acerb linkage between the two sugars ( fig.1 )
Fig.1 RNA bases linked by phosphodiester bonds between 3′-OH and 5′-C.
( RNA construction, n.d )
Structures of Deoxyribonucleic acid
Deoxyribonucleic acid ( deoxyrinucleic acid ) is the linear of nucleic acids which is composed of four different constructing blocks of bases and is deficiency of one O atom at carbon2 ‘ ( fig.2 ) and as a consequence it is named as deoxyribose sugar.
Fig.2 Structure of DNA.
( Deoxyribonucleic acid Structure, n.d )
Deoxyribonucleic acid is normally found in nucleous and scientist called Erwin Chargaff found that DNA has four base bases viz. pyrimidine ( C and T ) and purine ( adenine and G ) ( fig.3 )
Purines: a )
Adenine A Guanine G
Pyrimidines: B )
Thymine T Cytosine C
Fig.3.Structure of DNA bases.
( Deoxyribonucleic acid and RNA Structures, n.d )
The entire sum of pyrimidine base bases thymine+cytosine is ever equal to the entire sum of purine base bases adenine+guanine.The sum of T is ever equal to the sum of A ( A=T ) and the sum of C is ever equal to the sum of G ( Gi‚?C ) .But the sum of adenine +thymine is non needfully equal to the sum of guanine+cytosine.
( Gupta, P.K. , 2000 )
The Double Helix Structure
By the survey of x-ray diffration, Rosalind Franklin and Maurice Wilkens suggested that DNA has a coiling construction with a diameter of 20A and 34A distance in the spiral ( fig.4a ) . Deoxyribonucleic acid consists of two spiral which the two ironss are coiled around the same axis to organize a right-handed spiral and they can be separated from one another merely by uncoiling.
The anchor of altertnating deoxyribose and phosphate groups are placed outside the spiral confronting the surrounding H2O ( hydrophilic ) whereas the bases are inside the spiral ( hydrophobic ) and are set in a plane at right angle to the long axis.The right-handed Deoxyribonucleic acid signifiers are called B-DNA holding 3.4A distance between the two base braces and it has 10 base braces in each bend. Deoxyribonucleic acid can besides be as left-handed and since left-handed DNA follow a zigzag manner, it is called as Z-DNA.The chief difference between Z-DNA and B-DNA is that in Z-DNA, one complete spiral has 12 base braces per bend whereas B-DNA has merely 10 base braces per bend.
( Gupta, P.K. , 2000 )
Fig.4 ) a ) Structure of dual spiral, B ) Deoxyribonucleic acid construction demoing parallel and anti-parallel, degree Celsius ) dual spiral demoing minor and major channels.
( Deoxyribonucleic acid Structures, n.d )
In dual spiral, the two strands of DNA runs face-to-face in way ie,5 ‘ — – & A ; gt ; 3’and 3 ‘ — – & A ; gt ; 5 ‘ which means the two strands should be parallel or anti-parallel to do the stabilised construction and keep the two polynucleotides together.There is an interaction of base-pair between the A on one strand and a T on the other ( A=T ) and likewise between C and G ( Gi‚?C ( fig.4b ) with H bond two and three rrespectively.These coupling of this two strands creates minor and major channels on the surfaces of dual spiral ( fig.4c ) .
In DNA dual spiral, one strand act as parent strand and the other new strand as templet which
synthesise complementary girl strands ( fig.5 ) .The dual spiral is hold together by H-bonding between complementary base braces and base stacking interaction. ( Voet, D. Et Al
Fig.5 DNA reproduction. Each strand of a parental Deoxyribonucleic acid Acts of the Apostless as a templet for the synthesis of a complementary girl strand.
( Voet, D. et al,2006 )
Structure of RNA
RNA ( ribonucleic acid ) is the 2nd type of nucleic acid found in throuhtout the cell. In instance of RNA, it has a sugar and an -OH group at 2 ‘ C atom ( fig.6 ) .
Fig.6 Structure of ribose.
( RNA Structure, n.d )
Similarly, RNA has besides four nucleotide bases as purine and pyrimidine ( fig.7 ) except the T is replaced by U in pyrimidine.
Adenine A Guanine G
Uracil U Cytosine C
Fig.7 Structures of RNA bases.
( RNA and DNA Structures, n.d )
Though RNA is individual -stranded construction, when RNA fold back on itself, by opportunity or
occasional base coupling and H bonding, it forms some of a mated coiling construction ( fig.8 ) which consequences in three dimensional construction and they are copmplex and alone. They form intra-strand base brace from self complementary part along the concatenation.
Fig.8 Base coupling within a individual strand of RNA demoing a possible folded construction.
( RNA Structure, n.d )
The information from RNA determines the protein synthesis through the series of interlingual rendition which involves three types of RNA molecules to execute different maps:
1 ) Messenger RNA ( messenger RNA ) Structure
Messenger RNA ( messenger RNA ) is a additive sequence of amino acid in polypeptide concatenation and has longer concatenation than the reading frame that has to be translated.To Begin and terminal interlingual rendition, specific start and stop codons are required. Mostly mRNAs has start ( instigator ) codons AUG that can be served as methionine codon at 5’carbon.. Occasionally GUG and CUG can alsobe used as instigator codon in some of the bacterial and eucaryotic messenger RNA severally. GUG codifications for valine and CUG for leucine to originate a protein concatenation. The halt codon are UAA, UGA and UAG and do non code for any aminic acid. The stop codon indicates that interlingual rendition is to be terminated and the ribosome has to be released polypeptide merchandise. The sequence of start and halt codon are called a reading frame. Codon holding overlapping information, messenger RNA can be translated to different reading frames and formed different polypeptides ( fig.9 ) . Each familial codification specifies different aminic acids and seldom unusual cryptography occurs.
( Lodish, etal, 1986 )
5’a”ˆa”ˆ GCU UGU UUA CGA AUU A a”ˆ messenger RNA
a”ˆa”ˆa”ˆ Ala Cys Leu Arg Ile a”ˆa”ˆa”ˆ polypeptide 1
5’a”ˆa”ˆ G CUU GUU UAC GAA UUA a”ˆa”ˆ messenger RNA
a”ˆa”ˆa”ˆ Leu Val Tyr Glu Leu a”ˆa”ˆa”ˆa”ˆ polypeptide 2
Figure 9 ; Multiple reading frames in an messenger RNA sequence
( Lodish, etal, 1986 )
2 ) Transportation RNA ( transfer RNA ) Structure
Transportation RNA ( transfer RNA ) is an adapter molecule that serve as a span between messenger RNA and the amino acids taking to the Polypeptide chain.tRNA exists in primary, secondary and third construction. A tRNA molecule is chemically linked to aminic acids through a bond organizing an aminoacyl-tRNA. The general construction of transfer RNA is represented by Cloverleaf theoretical account ( fig.10 ) . The anticodon at the underside is complementary to the messenger RNA codon with the coupling of base to it. Due to the presence of mRNA codon and transfer RNA anticodon, base-pairing is in anti-parallel directions.Amino acids are attached to the acceptor root at the 3 ‘ end point holding sequence CCA and protrudes beyond the 5 ‘ terminal. The dihydrouracil cringle ( D cringle ) contained ever uracil base and TCG cringle has invariant sequence of bases.Variable cringle has fluctuation in both bases composing and in length. ( Lodish, et al,1986 )
Fig.10. Structure of transfer RNA.
( RNA-Ribonucleic acid, n.d )
3 ) Ribosome RNA ( rRNA ) Sructures
Ribosome RNA ( rRNA ) carries ribosome atoms and consists of one little and one big fractional monetary unit ribosome and protein. The rRNA is the largest construction among the RNAs. Each of the fractional monetary units composed of one to three rRNA s types and every bit many as protein constituents. Comparing to procaryotes, eucaryotic cells are larger and more atoms whereas the eucaryotes has 40s and 60s with 80s for complete ribosome.
Functions of Deoxyribonucleic acid
• DNA service as a storage stuffs for familial information in all life cells.
• Due to the dual coiling construction, DNA provides more stableness hive awaying more familial information since the dual bond required more force to interrupt up the constructions.
• DNA is constructing block of the protein synthesis which takes by the procedure of Central Dogma relationship.Genetic information from the Deoxyribonucleic acid is transcribed to mRNA transporting the familial codon and subsequently translated to the polypeptide concatenation.
• DNA provides for long term storage of familial information due to the presence of deoxyribose sugar at 2’carbon, therefore forestalling the formation of cyclic phosphate ester since H can non hydrolysis the phosphodiester bond, whereas 2’hydroxyl group in RNA act as a nucleophile assailing the phosphodiester bond and consequences in less efficiency of hive awaying information.
( Lodish, ea al,1986 )
• DNA act as templet or semiconservative.During the reproduction of dual spiral, DNA double strsnded DNA that consists of one old ( templet ) strand and one new girl strand. two ddaughter duced pronew girl strand.This two new DNA molecules is indistinguishable to the parents molecule and this type of preservation of old templet strand is called semiconservative.
• The major and minor channels formed during the coiling or wounding of duoble strands provides the reading of protein binding DNA.s
( Lodish, etal, 1986 )
Function of messenger RNA:
• messenger RNA carries familial information which is transcribed from DNA in a additive sequence of amino acid to a peptide concatenation.
• messenger RNA carries three codons for a specific amino acids.AUG act as start codon for a specified amino acids at 5 ‘ and UAA, UAG and UGA as stop codon or expiration of interlingual rendition.
Function of transfer RNA:
• The chief map of aminoacyl-tRNA is to recognize the specific codon for the activation of right aminic acids.
• transfer RNAs make certain that the amino acid are placed in right sequence to the turning peptide concatenation during the interaction of codon with the specific anticodon.
• Helps in Abinding the turning peptide concatenation to the ribosome during interlingual rendition procedure.
( Conn, E.E.,1987 )
Function of rRNA:
• rRNA could function as templet RNA.
• rRNA with ribosome atoms provides forms and construction during protein synthesis.
It besides helps in rushing or catalyzing the chemical reaction by enzyme called ribozymes.
The chief difference between the DNA and RNA constructions are that DNA has deoxyribose sugar and deficiency one O at C 2 ‘ , wheraes in RNA has ribose sugar and one -OH group attached at C 2 ‘ . Deoxyribonucleic acid is dual stranded in nature, supplying more stableness than individual stranded RNA. Again one large difference is that the presence of T in DNA and U in RNA srtucture.
The chief difference in the map of DNA and RNA is that the DNA maps chiefly for the storage of familial informations and the RNA as written text and interlingual rendition of familial informations.
Since the DNA is dual spiral that lesion around the plane of the spiral concealing the base -paired inside the spiral that prevents from reaching with H2O ( hydrophobic ) this base partner offing interaction provides more stableness to the nucleic acids hive awaying more familial information.In both
Deoxyribonucleic acid and RNA base partner offing between Gi‚?C provides more stronger and stable bond than the A=T since it requires more force to interrupt up the three H-bonding of Gi‚?C than the A=T.
In DNA, T is present and alternatively of thymine U is replaced in RNA.Since T contain methyl group, this base act as a protection and moreover methyl is strongly impersonal. It is methylated group and methylation freshly suppresses the migration of Deoxyribonucleic acid sections. These all grounds provides that DNA is strongly stable than RNA nucleic acid. Again methylation can assist in placing the parental ( templet ) strands from freshly synthesized strands in DNA strands.
Each of the 3’end of the sugar are used to originate the familial exchange and this point act as primer for DNA reproduction.
The fond regard of more ribosome on messenger RNA provides high deposit rate than the unattached ribosomes which means the polyribosome or polysome composites are actively synthesising protein than individual ribosomes.
( Strickberger, M.W.,1976 )