Deoxyribonucleic acid and RNA are long additive concatenation polymers, called nucleic acids, composed of monomers called bases. It is found in all the beings which act as familial information transporting molecules that can be passed from one coevals to the following. These supermolecules consisted of a big figure of linked bases, each nucleic acid composed of furanose ( pentose ) sugar, a phosphate, and a base ( purines or pyrimidines ) . The sugars are linked to each other by glycosidic bond, organizing a common anchor for structural function. The bases sequence in both molecules carries familial information.
Deoxyribonucleic acid is a dual spiral molecule. During the reproduction, one of strand Acts of the Apostless as templet forming complementary additive strand of RNA and transferred information to the messenger RNA ( written text ) . From here the information was carried for the synthesis of protein through the exact sequences of amino acids ( interlingual rendition ) . Therefore, we can corroborate that DNA is information transporting molecules and RNA as a catalyst/intermediate for the protein synthesis. Therefore, the flow of familial information, cistron look in normal cell is
Deoxyribonucleic acid and RNA are the nucleic acid nowadays in the karyon and cytol of an being but DNA is besides found in the chloroplast of works, which acts as familial information transporting molecules in the exact sequence of their bases. These molecules are additive polymers composed of monomers called bases. Both the molecules have three chief constituents in the structures- pentose sugar, nitrogen-bearing bases, and the phosphate group attached at 5 iˆ?carbon, as mentioned above. The chemical construction of individual stranded Deoxyribonucleic acid and RNA shows hydroxyl group at 3A? terminal and a phosphate group at 5A? terminal of C. The next bases are linked to each other by phosphodiester bond, one on the 5A? side of the phosphate and another on the 3A? side of the hydroxyl group. ( Lodish et Al, 2008 ) The construction of DNA is similar to RNA, but non indistinguishable to each other. In 1953, James D. Watson and Francis H. C. Crick proposed that DNA has a dual spiral molecule, based on analysis of x-ray diffraction forms. Deoxyribonucleic acid consists of two associated polynucleotide strands that air current together to organize a dual spiral. The two sugar phosphate anchors are on the exterior of the dual spiral, and bases project into the inside. The bordering bases in each strand stack on top one another in parallel planes but the orientation of two strands are in anti-parallel, that is, their 5A? to 3A? waies are opposite. ( Nelson & A ; Cox, 2000 ) But RNA exists in individual stranded. Their bases are in the linear signifiers which has codon at 5 iˆ? . The furanose sugar nowadays in DNA is deoxyribose, whereas RNA has ribose sugar. The deoxyribose sugar contained H at 2 iˆ?carbon of DNA which makes different from ribose sugar which contained OH-group at 2 iˆ? in RNA. The common bases present in the Deoxyribonucleic acid and RNA are adenine ( A ) and G ( G ) – purines, which contain a brace of amalgamate rings, and the bases cytosine ( C ) – pyrimidines, holding a individual ring. But DNA contained thymine alternatively of U in RNA. In the complementary strand, A ever pairs thymine/uracil with two H bonds and guanine brace ‘s C with three H bonds. The bases are on the 1 iˆ? C of pentose sugar. ( Berg et al, 2006 )
Figure2: Chemical construction of DNA. Figure 3: Chemical construction of RNA.
( Synergistic Concepts in Biochemistry, 2002 ) ( Synergistic Concepts in Biochemistry, 2002 )
In normal signifier of DNA, the infinites between the intertwined strands form two coiling channels of different breadths, major channels ( larger ) and minor channels ( smaller ) . The Deoxyribonucleic acid semidetached house is held together by two forces ; hydrogen bond between complementary base braces and base stacking interactions or hydrophobic interactions. Since RNA is a individual isolated molecule it does hold channels in its construction. ( Berg et al, 2006 ) . The normal DNA in the cells is a right handed spiral. The x-ray diffraction form of Deoxyribonucleic acid reveals that the stacked of bases are on a regular basis spaced 3.4A apart along the spiral axis. The spiral makes a complete bend every 34A and 10 base braces per bend. There is a rotary motion of 36 degree per base ( 360 grades per full turn/ 10 bases per bend. Deoxyribonucleic acid can happen in different three dimensional signifiers since it is a flexible molecule. The secondary and third construction of DNA is A- , B- , C-and H-forms, classified harmonizing to their characteristic constructions or spirals. All plays the same maps in the ordinance of look of cistrons or familial information. ( Nelson & A ; Cox, 2000 ) RNA besides forms three-dimensional constructions, by the complementary base coupling within a additive sequence ; G pairs with C and A brace with U organizing the secondary constructions like hairpin cringle, root cringle, and third construction like pseudoknot and so on. Weak interactions, particularly base-stacking interactions play a major function in stabilising RNA constructions. A-form right handed dual spiral ( complementary sequence ) and Z- signifier like DNA have been existed but B-form of RNA has non been observed. RNA is found in three signifiers ( messenger RNA, transfer RNA, and rRNA ) and their differences in constructions and maps are given below. ( Lodish et Al, 2008 )
Figure4: Deoxyribonucleic acid dual spiral. Figure 5: Secondary Structure of RNA
( Synergistic Concepts in Biochemistry, 2002 ) ( Secondary Structure of RNA, n.d )
Function of DNA and RNA based on its construction
General map of DNA and RNA
Deoxyribonucleic acid is a familial stuff that controls all the cell activities. From the construct of Central Dogma of Molecular Biology, DNA shops the familial information for protein synthesis. In the procedure of written text, one of the DNA dual strands acts as a templet for the synthesis of complementary strand of RNA by replacing all T by U. Transcription of DNA is carried out by RNA polymerase, which adds one ribonucleotide at a clip the 3A? of turning RNA concatenation. The sequence of the templet DNA strand determines the order in which ribonucleotides are polymerized to organize an RNA concatenation. ( Hartl & A ; Jones, 2005 ) The chief map of RNA is to synthesise the proteins by exact sequencing of aminic acids. The information stored in DNA is copied into ribonucleic acid during written text, and so to the protein by interlingual rendition. Translation is the procedure by which the linear nucleotides sequence of an messenger RNA is used as a templet to fall in the amino acids in a polypeptide concatenation in the right order. Three types of RNA take parts to execute different but concerted maps in the protein synthesis. ( Alberts et al, 2008 )
Hydrogen at 2A?carbon in deoxyribose and OH-group at 2 iˆ? in ribose
Deoxyribonucleic acid evolved as bearer of familial information or its map in long term storage of familial information because the H at 2A?position in the deoxyribose of DNA makes it far more stable molecule than RNA. Hydrogen can non assail and hydrolysis the phosphodiester bond, forestalling the formation of the cyclic phosphate ester. Therefore, stableness of DNA construction will be maintained in order to hive away information for longer clip. Whereas, RNA have an OH-group attached at the 2A?carbon of ribose. These 2A?-hydroxyl groups in RNA act as nucleophile, assailing the phosphodiester bond. It consequences in less opportunity of hive awaying the information. ( Lodish et Al, 2008 ) But this hydroxyl group on C2 of ribose makes RNA more chemically labile by assailing and hydrolysis the phosphodiester bond at impersonal pH. This stableness cleaves RNA into mononucleotides by alkalic solution. The C2 hydroxyl group of RNA provides a chemically reactive group that takes portion in RNA- mediated contact action. As a consequence, RNA like ribosomal RNA plays a catalytic function in the formation of peptide bond, by exact sequencing the amino acids during protein synthesis. Hence, flow of information is accurate. ( Lodish et Al, 2008 )
Thymine in DNA and U in RNA
Thymine is more of import in Deoxyribonucleic acid because it contains methyl group ( -CH3 ) which remains impersonal. By holding T in DNA in topographic point of U ( in RNA ) , cells ensures to mend damaged DNA, caused by the deaminization of C to uracil without doing other alterations in the Deoxyribonucleic acid molecule. It will besides better the long term stableness of DNA constructions, since T is inactive base. Therefore, familial information gets shop for longer clip. If uracil is present in the Deoxyribonucleic acid, it prevents the repairing of damaged DNA and mistake will happen during written text. ( Becker et al, 2006 ) Presence of U in RNA besides plays of import functions ( absent in DNA ) . RNA easy gets folded forming secondary construction. During folding, uracil gets brace with A in which they will stabilise the secondary construction of RNA. Presence of uracil aids in heightening the smooth flow of familial information in the exact sequence of aminic acids during protein synthesis. Uracil is besides a reactive base since it does non hold a methyl group that prevents the renaturation of spiral. In that manner being receives immediate familial information. ( Lodish et Al, 2008 )
Deoxyribonucleic acid map base on channels
We know that secondary and third construction of DNA contain two different channels ; major ( larger ) and minor ( smaller ) channels. These channels provide infinite for other strands of nucleic acid and besides for binding of regulative proteins. ( Bhagavan, 2002 ) Whereas RNA does hold channels since it is individual isolated molecule.
Deoxyribonucleic acid is a dual spiral and RNA a individual stranded molecule
The dual spiral facilitates the accurate transmittal of familial information. The dual spiral construction and presence of specific base brace replicates the familial information accurately. The basal sequence of one strand determines the sequence of other strand such that G of one strand ever pairs with C of other strand and so on. Therefore, if dual spiral separated into two constituent ironss it consequences two individual strand templets. For this, new dual spirals could be constructed, each of holding the same bases sequence as the parent dual spiral. In a manner, as Deoxyribonucleic acid is replicated one of the ironss of each girl DNA molecule is synthesized, and other passed unchanged from the parent DNA molecule. Hence, a character is maintained between the two which means accurate transmittal of information is occurred through dual spiral of Deoxyribonucleic acid. ( Berg et al, 2006 ) RNA is a individual strand linear concatenation molecule. This individual strand anchor is flexible. Therefore, the polymer concatenation can flex back on itself to let one portion of the molecule to organize weak bond with another portion of the same molecule, ensuing folding of RNA concatenation which so into a specific form based on its exact sequence. Then the form of RNA recognizes other molecules by selective binding and even catalyse chemical alterations in the molecules that are bound. Exact sequencing of bases, that is, sequence of amino acid in the polypeptide concatenation consequences in accurate transportation of familial information during protein synthesis. ( Alberts et al, 2008 )
Double spiral of DNA hides the bases inside because of hydrophobic in nature, which means it does non let H2O molecules to acquire enter into the construction. Presence of deoxyribose sugar and base stacking will forestall the Deoxyribonucleic acid construction from chemical onslaught. In that instance, stableness of construction will be maintain and shops information for longer clip. ( Nelson & A ; Cox, 2008 ) The presence of individual strand and ribose sugar in RNA is helpful in rapid transferring of information for the protein synthesis. ( Alberts et al, 2008 )
Three types of RNA – constructions and its maps
Structures of RNAs
Messenger RNA is the template signifier for protein synthesis. It is a heterogenous category of molecules with an mean length of 1.2kilobases. The messenger RNA exists in additive polymers with codon for protein synthesis. In 5A? or N-terminus of additive polymers, methionine, AUG codon act as start codon and halt codon at 3A? or C-terminus with UAA, UAG and UGA three codons. Between this two points, present the reading frame, where sequencing of amino acid occurs. 5I„ cap is found at N-terminus which binds with proteins and poly A-tail at C-terminus of additive messenger RNA. The messenger RNA has secondary construction, root cringle formed by complementary base brace of additive base sequence. ( Lodish et Al, 2008 )
Figure7: – Structure of messenger RNA. ( Synergistic Concepts in Biochemistry, 2002 )
Here in transportation RNA, it is a little RNA species independent of ribosome that is charged with an amino acid at one terminal ( 3A?end ) and another terminal coated with anticodon. The tRNA exist in all degrees ; primary ( additive ) , secondary ( stem cringles ) and third construction ( 3-dimension ) . All tRNAs portion a common construction during the map, represented by cloverleaf. They have four base-paired roots, holding three stem loops- dihydrouracil cringle ( D cringle ) on left, antidon cringle at underside holding three letters, anticodon at its vertex T cringle with sequence of the bases the acceptor root and acceptor cringle on the top. ( Weaver, 2002 ) . The tRNAs portions a common three dimensional form, which resembles an upside-down L. This form maximizes stableness of run alonging up the base brace in the D root with those in the anticodon root, and the bases T root braces with those of acceptor root. The aniticodon bases are stacked and projecting out to the right from the side of anticodon cringles and twisted into a form in order to establish braces with complementary codon of messenger RNA. The construction of transfer RNA is stabilized by third interactions like base-base, base- anchor and anchor. ( Weaver, 2002 )
Figure6: Secondary construction of transfer RNA. ( Secondary Structure of transfer RNA, n.d )
In the instance of Ribosomal RNA, it forms a nucleus of ribosome, cell ‘s indispensable protein mill. It is found most copiously and stable signifier, represents about 70-80 % of entire cellular RNA. Three types of rRNAs found in procaryotes are 5s, 16s and 23s, base on their deposit behaviour. ( Lodish et Al, 2008 ) In eucaryotes, four different size of rRNA is found- 5s, 5.8s, 18s and 28s. The rRNA exists every bit coiling construction formed by turn uping of a individual isolated polymer but does non be as a two-base hit stranded polymer. The rRNA exists in several conformations because of no stiff and stable dual coiling construction like DNA. In procaryotes, ribosome binds to the messenger RNA near to the interlingual rendition start site. That ribosome binding site is referred to as Shine-Dalgarno sequence or as the ribosome acknowledgment component. In eucaryotes, ribosome binds at 5A? terminal of the messenger RNA and scan down the messenger RNA until they encounter a suited codon. ( Weaver, 2002 )
Function of messenger RNA
During written text, information stored in DNA is copied into messenger RNA. The messenger RNA carries information from Deoxyribonucleic acid in a codon to the ribosome. The interlingual rendition begins at start codon, methionine ( AUG ) . The interlingual rendition begins from the 5A?end, where codon runs from the specific start codon to a halt codon which is in 3A?or c- end point of polypeptide concatenation, called reading frame. Each amino acid is encoded by one or three codons in messenger RNA and each codon specifies one amino acid. The methionine, AUG codon ( start codon ) specified aminic acid at 5A? but three stop codons ( UAA, UAG, UGA ) specified no amino acids, which is expiration of interlingual rendition. The uninterrupted codon sequence in transfer RNA ( reading frame ) between the start codon and halt codon is translated into additive sequence of amino acids which in bend consequence in protein synthesis. ( Lodish et Al, 2008 )
Functions of transfer RNA
transfer RNA is chiefly for decrypting map.
1 ) transfer RNA bear downing – As discussed in construction, transfer RNA has two chief terminal ; one terminal with acceptor root and other with anticodon. The acceptor root accepts and covalently bound to specific amino acids, called transfer RNA charging ( charged with aminic acids ) . Charging takes topographic point by two stairss, both catalyzed by the enzyme, aminocyl- transfer RNA synthetase.
Amino acid is activated utilizing ATP, forms an aminoacyl-AMP and pyrophosphate.
Energy stored in aminoacyl-AMP is used to reassign energy from aminic acid to tRNA ensuing formation of aminocyl-tRNA. This function was played by aminoacyl-tRNA synthetase but it besides determines the charge specificity. Merely 20 synthetases existed, one for each amino acid which is really specific. If acceptor root receives incorrect aminic acids, it consequences more mistake in protein synthesis. ( Weaver, 2002 )
2 ) Anticodon- Anticodon cringle is present at underside of tRNA secondary construction with anticodons. Anticodons of tRNA get paired with codons of messenger RNA. The activated amino acid ( encoded by codons in messenger RNA ) can be added to the turning polypeptide concatenation. This is specific and regulated by an enzyme, aminoacyl-tRNA synthetase. Normally, base partner offing between two RNA occurs in 3rd ( 3A? ) base in an messenger RNA codon and the first ( 5A? ) base in tRNA anticodon. If incorrect amino acid is acquiring attached to tRNA, there occurs immediate remotion of aminic acids. Specific or connate transfer RNA with aminic acid delivers correct protein synthesis. ( Lodish et Al, 2008 )
Function of rRNA
As mentioned in its construction, it is used in constructing up of ribosome, the complex construction which moves along an messenger RNA molecule. Usually ribosome is bind with messenger RNA at 5A? terminal. ( Weaver, 2002 ) This binding checks the suited codon of messenger RNA. The rRNA catalyzes the assembly of aminic acids into polypeptide ironss. They besides bind transfer RNA and other accoutrement proteins for protein synthesis. The rRNA besides plays a catalytic function in the formation of peptide bonds during protein synthesis. ( Lodish et Al, 2008 )
However, DNA and RNA both are supermolecules holding similar constructions. But they are non indistinguishable to each other. Each of their constructions play a peculiar map. Both occur in three dimensional constructions but RNA exists in three signifiers, each signifier differing from other, holding different constructions and maps. Over all, they perform different maps, but for the protein synthesis. Hence, DNA and RNA are nucleic acids found in all life beings, which act as information carrying molecules for the protein synthesis.