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Why deoxyribose for DNA and ribose for RNA?

Why deoxyribose for DNA and ribose for RNA?


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Why is DNA made out of deoxyribose and RNA made of ribose? Why can't they both use ribose or deoxyribose? I think that the deoxyribose gives an advantage in storing genes, the job of DNA and ribose is better dealt with outside the nucleus… but why?


Nice question which leads to the fundamentals of DNA and RNA.

DNA (Deoxyribonucleic acid) is the core of life in Earth, every known living organism is using DNA as their genetic backbone. DNA is so precious and vital to eukaryotes that its kept packaged in cell nucleus, its being copied but never removed because it never leaves the safety of nucleus. DNA directs all cell activity by delegating it to RNA. RNA (Ribonucleic acid ) have varied sort of biological roles in coding, decoding, regulation, and expression of genes. RNA carries messages out of the cell nucleus to cytoplasm.

The structure of RNA nucleotides is very similar to that of DNA nucleotides, with the main difference being that the ribose sugar backbone in RNA has a hydroxyl (-OH) group that DNA does not. This gives DNA its name: DNA stands for deoxyribonucleic acid. Another minor difference is that DNA uses the base thymine (T) in place of uracil (U). Despite great structural similarities, DNA and RNA play very different roles from one another in modern cells.

http://exploringorigins.org/rna.html

RNA has three main characteristics that differs it from DNA

  • RNA is very unstable and decomposes rapidly.
  • RNA contains Uracil in place of Thymine
  • RNA is almost always single stranded.

DNA and RNA use a ribose sugar as a main element of their chemical structures, ribose sugar used in DNA is deoxyribose, While RNA uses unmodified ribose sugar.

Ribose and Deoxyribose


From the fig above we can see that the principal difference between the two molecules is the presence of OH in ribose (2' tail) and absence in deoxyribose. There is a difference in one Oxygen atom as the name stands de-oxy ribose. Both Ribose and deoxyribose have an Oxygen(O) atom and a Hydrogen (H) atom (an OH group) at their 3' sites. The OH groups are very reactive in nature, so the 3' OH tail is required for phosphodiester bonds to form between nucleotides in both ribose and deoxyribose atoms.


Answer

DNA is such an important molecule so it must be protected from decomposition and further reactions. The absence of one Oxygen is the key for extending DNA's longevity. When the 2' Oxygen is absent in deoxyribose, the sugar molecule is less likely to get involved in chemical reactions( the aggressive nature of Oxygen in chemical reactions are famous). So by removing the Oxygen from deoxyribose molecule, DNA avoids being broken down. In an RNA's point of view the Oxygen is helpful, unlike DNA, RNA is a short-term tool used by the cell to send messages and manufacture proteins as a part of gene expression. Simply speaking mRNA (Messenger RNA) has the duties of turning genes ON and OFF, when a gene needed to be put ON mRNA is made and to keep it OFF the mRNA is removed. So the OH group in 2' is used to decompose the RNA quickly thereby making those affected genes in OFF state.

Finally, the ribose sugar is placed in RNA for easily decomposing it and DNA uses deoxyribose sugar for longevity.

References

Flesh and Bones of Metabolism - Marek H. Dominiczak

Genetics For Dummies - Tara Rodden Robinson


Addition to Jvrek's answer based on the comments. Most RNA degradation mechanisms catalysed by different RNAses (RNAse-A and RNAse-S, for example), involve the 2'-OH. Therefore the repertoire of RNAses is selective towards RNA and not DNA because of the 2'-OH.


Why DNA for the genetic material?

I think the correct and sufficient answer to this is the one so frequently repeated that it is difficult to find the original source. For example, G.F.Joyce wrote in a 2002 Nature review article:

The primary advantage of DNA over RNA as a genetic material is the greater chemical stability of DNA, allowing much larger genomes based on DNA.

To expand, RNA is unsuitable for large genomes because the 2'-OH of ribose (obviously absent from the 2'-dexoyribose of DNA) renders the phosphodiester bond susceptible to alkaline hydrolysis (see illustration adapted from Wikipedia article).

This will occur slowly at pH 7.6, but at a rate calculated to be sufficient to degrade a 1000 nucleotide RNA in about 70 days. This explains why all RNA viruses have small genomes (and why some, like flu virus, are segmented).

Why RNA for other informational functions?

There are a variety of ad hoc arguments here, but none as conclusive as the argument above for DNA. This is partly because there are a variety of functions RNA performs - one can make different arguments for each. Before making a point that I don't think has been made above, I would say that RNA most likely preceeded DNA (whether or not one believes it preceeded protein) and that there would have had to be a selective advantage for organisms to switch from RNA to DNA. One can see that for the genome, but not for the other functions.

This argument also applies catalysis, but in a slightly different way. If RNA enzymes (ribozymes) preceeded protein enzymes, most ribozymes have been dumped because protein enzymes are more efficient and organisms which developed them were at an advantage. Those that are left are so intimately involved with RNA that replacement by proteins would have been difficult. So answers to this question about DNA not being able to replace catalytic RNA, though correct, seem to me peripheral the general question of RNA function.

The central function of RNA is surely in protein synthesis - mRNA, rRNA, tRNA. One thing that these perhaps have in common is a three-dimensional structure that differs from an extended double helix. (Yes mRNA has tertiary structure too.) RNA lends itself more readily to such structures because the chemical difference between ribose and deoxyribose leads to a different helical structure (A-helix) from that of DNA (B-helix). To quote Fohrer et al.:

The presence of the ribose 2'-hydroxyl group in RNA engenders a preference for the C3'-endo puckering, thereby providing the decisive factor for the differences in conformation, hydration and thermodynamic stability between canonical RNA and DNA helices.

(Image from Niel Henriksen showing C3'- and C2'-endo pucker of ribose. C2'-endo pucker is found in deoxyribose in the B-DNA helix.)

The RNA A-helix involves less stringent base-pairing than the DNA B-helix (hence the greater error frequency in replicating RNA virus genomes), which is also reflected in non-WC base-pairing in rRNA and tRNA. (The presence of U in RNA, rather than T in DNA should also be mentioned - GU base-pairs are found frequently in rRNA.)


Basically, it is because DNA is so hydrophobic that it does not substantially catalyse reactions in aqueous solutions.

RNA is less hydrophobic and therefore more able to catalyse aqueous reactions, but the same reactivity means that it is more susceptible to degradation and so less suited than DNA to the storage of genes.

RNA is more polar and therefore less hydrophobic than DNA because of the increased polarity of the extra hydroxyl group in ribose compared to deoxyribose.

This means that DNA is more stable than RNA, because the strands are harder to separate because they are more attracted to each other than the surrounding water. Because it is more stable it is more suited to storing genetic sequences with less degradation than RNA.

But because DNA is so stable it requires a substantial amount of machinery just to separate and keep separated the strands when they are needed. It is therefore unlikely DNA was the original genetic material that came about via much simpler prebiotic chemistry.

RNA being more polar is easier to separate. It also unlike DNA can actually catalyse a wide variety of reactions requiring only the RNA and some prebiotic chemistry such as metallic ions or simple fatty acids.

For instance the group I intron can catalyse single electron transfer in the presence of Iron (II) ions. And it can catalyse its excision from a section of RNA with Iron (II) or more commonly magnesium ions. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3365117/

In fact in almost every highly conserved biological process you will find remanent RNA chemistry if not small pieces of RNA held by proteins doing the heavy lifting. This leads to the RNA world hypothesis, which posits that RNA emerged before DNA and before proteins. https://www.youtube.com/watch?v=U6QYDdgP9eg

But being easier to separate RNA is more susceptible to degradation by aqueous reagents, and being less stable is less suited to the storage of genes without degradation. So if an organism found a way to turn its RNA to DNA for storage and back again it would have a significant selective advantage.

Such a mechanism might be as simple as protein or ribozyme that could preferentially hold DNA in contact with RNA. Then the normal mechanisms of strand ligation could work both to produce DNA from RNA templates and RNA from DNA templates.

Over time there would tend to arise specialised versions to do each task, but each building on the original holding mechanism, which itself could have built on the ligase mechanism. Today there are a number of highly related small DNA and RNA binding RNAs involved in many analogous processes. Search for RNA Structure, Function and Recognition by Anna Marie Pyle on iBioseminars.

I would link some more, but I don't have the reputation. But see also "The Origin of the Genetic Code" by cdk007 in the same series. Also there is an excellent 3 videos on abiogenesis, RNA and fatty acid vesicle "protocells" by Jack Szostak on ibiology. Just search for them.


6.2: DNA and RNA

  • Contributed by Suzanne Wakim & Mandeep Grewal
  • Professors (Cell Molecular Biology & Plant Science) at Butte College

This young person has naturally red hair. Why is this hair red instead of some other color? And, in general, what causes specific traits to occur? There is a molecule in human beings and most other living things that is largely responsible for their traits. The molecule is large and has a spiral structure in eukaryotes. What molecule is it? With these hints, you probably know that the molecule is DNA.

Figure (PageIndex<1>): Red hair


Nucleic acids are composed of linked nucleotides. DNA includes the sugar, deoxyribose, combined with phosphate groups and combinations of thymine, cytosine, guanine, and adenine. RNA includes the sugar, ribose with phosphate groups and combinations of uracil, cytosine, guanine, and adenine.

DNA and RNA are nucleic acids and make up the genetic instructions of an organism. Their monomers are called nucleotides, which are made up of individual subunits. Nucleotides consist of a 5-Carbon sugar (a pentose), a charged phosphate and a nitrogenous base (Adenine, Guanine, Thymine, Cytosine or Uracil). Each carbon of the pentose has a position designation from 1 through 5. One major difference between DNA and RNA is that DNA contains deoxyribose and RNA contains ribose. The discriminating feature between these pentoses is at the 2&prime position where a hydroxyl group in ribose is substituted with a hydrogen.

DNA has a double-helical structure. Two antiparallel strands are bound by hydrogen bonds.

The following video illustrates the structure and properties of DNA.

DNA is a double helical molecule. Two antiparallel strands are bound together by hydrogen bonds. Adenine forms 2 H-bonds with Thymine. Guanine forms 3 H-bonds with Cytosine. This AT & GC matching is referred to as complementarity. While the nitrogenous bases are found on the interior of the double helix (like rungs on a ladder), the repeating backbone of pentose sugar and phosphate form the backbone of the molecule. Notice that phosphate has a negative charge. This makes DNA and RNA, overall negatively charged.

There are 10 bases for every complete turn in the double helix of DNA.


Difference between Deoxyribose and Ribose

Deoxyribose and Ribose are simple sugars that form a part of nucleic acids that are one of the important macromolecules present in all living organisms. Just like proteins and carbohydrates, nucleic acid is also a vital for survival of all living organisms.

Deoxyribose is an aldopentose, which means a pentose sugar with an aldehyde functional group in position. An aldehyde group consists of a carbon atom that is bonded to a hydrogen atom and double-bonded to an oxygen atom (chemical formula O=CH-).

Deoxyribose is derived from ribose. Ribose forms a five-member ring composed of four carbon atoms and one oxygen atom. Hydroxyl (-OH) groups are attached to three of the carbons. The fourth carbon in the ring, one of the carbon atoms adjacent to the oxygen, which is attached to the fifth carbon atom and a hydroxyl group. Deoxyribose is formed by the replacement of the hydroxyl group at the position, the carbon furthest from the attached carbon with hydrogen, leading to the net loss of an oxygen atom. Ribose has the chemical formula C5H10O5. Thus, deoxyribose has the chemical formula C5H10O4.

Deoxyribose and Ribose are both forms of simple sugars or monosaccharides that are found in the living organisms. They are of great importance biologically as they help to form the blueprint of the organism which is then passed on through generations. Any change in the blueprint in one generation of the species is manifested in the next in the form of physical or evolutionary changes. But ribose and deoxyribose have some subtle yet vital differences.

Deoxyribose –

Deoxyribose is also a form of pentose sugar but with one oxygen atom less. The chemical formula of deoxyribose sugar is C5H10O4. It is also an aldopentose sugar as it has an aldehyde group attached to it. The modification helps the enzymes present in the living body to differentiate between ribonucleic acid and deoxyribonucleic acid. The shape of deoxyribose sugar is such that four out of five carbon atoms along with an atom of oxygen form a five membered ring. The remaining carbon atom is attached to two hydrogen atoms and lies outside the ring. The hydroxyl groups on the third and fifth carbon atom are free to attach to phosphate atoms. As a result only two phosphate atoms can attach to deoxyribose sugar. Deoxyribose plus a protein base which can be either purine or pyramidine forms deoxyribonucleoside. When phosphate atoms attach to deoxyribonucleoside it forms deoxyribonucleic acid or the DNA. DNA is the store house of genetic information in all living organisms. Every organism has a different DNA which is responsible for the characteristic features of that species or organism. Changes in the DNA molecule brings about a change in the genetic make- up of the organism. DNA is a double helical structure composed of nucleotides attached in a spiral shape. Nucleotide is composed of a nitrogenous base, pentose sugar and phosphate. The arrangement of the nitrogenous base forms the genetic code for that organism.

This is a pentose sugar which has five carbon atoms and ten hydrogen atoms. Its molecular formula is C5H10O5. This is also known as aldopentose as it has an aldehyde group attached at the end of the chain in the open form. The ribose sugar is a regular monosaccharide in which one oxygen atom is attached to each carbon atom in the chain. On the second carbon atom, instead of hydrogen, hydroxyl group is attached. The hydroxyl groups on the second, third and fifth carbon atoms are free so that three phosphate atoms can attach there. The ribonucleoside formed by the combination of ribose sugar and a nitrogenous base becomes ribonucleotide, when a phosphate atom gets attached to it. The base can be either purine or pyramidine which are actually types of amino acids. Amino acids are building blocks for proteins. The ribonucleotide or ribonucleic acid (RNA) has three chiral centres and eight stereoisomers. The ribose sugar is found in the RNA of living organisms. The RNA is a single stranded molecule that winds around itself. RNA or ribonucleic acid is the molecule responsible for coding and decoding genetic information. In simple language it helps to copy and express the blue print of the organism and also helps in the transfer of genetic information to the progeny. They also help in protein synthesis.

Why Deoxyribose for DNA and Ribose for RNA?

DNA (Deoxyribonucleic acid) is the core of life in Earth every known living organism is using DNA as their genetic backbone. DNA is so precious and vital to eukaryotes that its kept packaged in cell nucleus, its being copied but never removed because it never leaves the safety of nucleus. DNA directs all cell activity by delegating it to RNA. RNA (Ribonucleic acid) have varied sort of biological roles in coding, decoding, regulation, and expression of genes. RNA carries messages out of the cell nucleus to cytoplasm.

DNA and RNA use a ribose sugar as a main element of their chemical structures, ribose sugar used in DNA is deoxyribose, and While RNA uses unmodified ribose sugar.


What is Deoxyribose

Deoxyribose is a pentose monosaccharide or simple sugar with the chemical formula of C5H10O4. Its name specifies that it is a deoxy sugar. It results from the sugar ribose by the loss of an oxygen atom. It has two enantiomers D-2-deoxyribose and L-2-deoxyribose. However, D-2-deoxyribose occurs widely in nature, but L-2-deoxyribose rarely originate in nature. It was discovered in 1929 by Phoebus Levene. D-2-deoxyribose is the main precursor of the nucleic acid DNA (deoxyribonucleic acid).


Structure

The chemical structures of both ribose and deoxyribose are given below. Looking at them, we can note the following points.

Similarities

► Ribose and deoxyribose are both monosaccharides or simple sugars.

► Both are aldopentoses, which means both are pentose sugar molecules which, in their open chain form, have an aldehyde functional group at one end. A pentose sugar is one that is made up of 5 carbon atoms.

Differences

► While ribose is a regular molecule of sugar, deoxyribose is a modified sugar. Deoxyribose is a deoxy sugar, which is derived from ribose by the loss of an oxygen atom. This is the reason the number of oxygen atoms in deoxyribose is one less than that in ribose. This difference makes it possible for enzymes to distinguish between the two sugar molecules.

► Ribose, like other aldopentoses, has three chiral centers, which makes it possible for ribose to have 8 different stereoisomers. 2-Deoxyribose, on the other hand, has two enantiomers (stereoisomers that are identical but non-superposable).


What is RNA?

RNA stands for ribonucleic acid.Its function is to carry out the instructions encoded in DNA. There are three types of RNA, each with a different function. These are:

Messenger RNA (mRNA)– mRNA carries information for protein synthesis from the DNA molecules in the nucleus to the ribosomes

Ribosomal RNA (rRNA)– rRNA is a structural component of ribosomes(the organelles that perform protein synthesis)

Transfer RNA (tRNA)– tRNA transfers amino acids to the ribosome. These amino acids are used to assemble a new polypeptide chain

RNA is made up of ribonucleotides,each containing a phosphate group, a 5-carbon sugar, and a nucleotide base. The four types of nitrogenous base found in RNA molecules are:

Therefore, the four types of RNA nucleotide are:

  • A nucleotide (containing adenine)
  • U nucleotide (containing uracil)
  • G nucleotide (containing guanine)
  • C nucleotide (containing cytosine)

Like in DNA molecules, these ribonucleotides are joined together by phosphodiester bondsthat form between the 3’ carbon of one sugar and the 5’ carbon of another. Unlike DNA, RNA is a single-stranded molecule however, it can still form double-stranded structures.

The base pairsin RNA molecules are:


RNA and DNA have ribose and deoxyribose sugars, respectively. How are these two sugars different from each other? a. Unlike ribose, deoxyribose does not have a hydroxyl group at carbon 1. b. Unlike ribose, deoxyribose does not have a hydroxyl group at carbon 2. c. Unlike ribose, deoxyribose does not have a hydroxyl group at carbon 3. d. Unlike ribose, deoxyribose does not have a hydroxyl group at carbon 4.

Q: Using the equations 2 Fe (s) + 3 Cl₂ (g) → 2 FeCl₃ (s) ∆H° = -800.0 kJ/mol Si(s) + 2 Cl₂ (g) → SiCl₄.

A: The reactions given are 1) 2 Fe (s) + 3 Cl₂ (g) → 2 FeCl₃ (s) ∆H° =.

A: Given , moles of Cl2 = 1.3 mol moles of HCl = 1.6 mol volume of flask = 250 .

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A: Why is 1-butanol, CH₃CH₂CH₂CH-OH, soluble in water, while heptane, CH₃(CH₂)₅CH₃, is not?

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A: The given reactant is piperidin-2-one. LiAlH4 is a reducing agent.

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A: The Nernst equation is shown below: Where: Ecell = cell potential E0cell = standard cell potential .

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A: Click to see the answer

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A: Photoelectric effect is produced by light striking a metal ad ejecting electrons from the metal's su.

A: The balanced reaction is: Molar mass of Cr2O3 = 152 g/mol Calculation of no. of mol of Cr2O3:

Q: The ethyl acetate concentration in an alcoholic solution was determined by diluting a 10.00-mL sampl.


DNA (Deoxyribose Nucleic Acid): Structure and Functions

DNA or deoxyribose nucleic acid is a helically twisted double chain polydeoxyribonucleotide macromolecule which constitutes the genetic material of all organisms with the exception of riboviruses.

In prokaryotes it occurs in nucleoid and plasmids. This DNA is usually circular. In eukaryotes, most of the DNA is found in chromatin of nucleus. It is linear. Smaller quantities of DNA are found in mitochondria and plastids (organelle DNA).

It may be circular or linear. Single-stranded DNA occurs as a genetic material in some viruses (e.g., coli-phage ф x 174). DNA is the largest macromolecule with a diameter of 2 nm (20A) and having a length in millimeters.

It is a long chain polymer of several hundred thousands of deoxyribonucleotides, e.g., 4.7 million base pairs in E.coli and more than 3 billion base pairs in human being. A DNA molecule has two un-branched complementary strands. They are spirally coiled. The two spiral strands of DNA are collectively called DNA duplex (Fig. 9.21).

The two strands are not coiled upon each other but double strand is coiled upon itself around a common axis like a rope or spiral stair case with base pairs forming steps (rungs) while the back bones of the two strands form railings.

Due to spiral twisting, the DNA duplex comes to have two types of alternate grooves, major and minor. One turn of 360° of the spiral has about 10 nucleotides on each strand of DNA. It occupies a dis­tance of about 3.4 nm (34A) i.e., pitch of DNA is 34A so that adjacent nucleotides or their bases are separated by a space of less than 0.34 nm (3.4 A).

A deoxyribonucleotide of DNA is formed by cross- linking of three chemicals—phosphoric acid (H3PO4), deoxyribose sugar (C5H10O4) and a nitrogen base. Four types of nitrogen bases occur in DNA.

They belong to two groups, purines (9-membered double rings with nitrogen at 1, 3, 7 and 9 positions) and pyrimidine’s (six membered rings with nitrogen at 1 and 3 positions). DNA has two types of purines (adenine or A and guanine or G) and two types of pyrimidine’s (cytosine or С and thymine or T).

Depending upon the type of nitrogen base, DNA has four kinds of deoxyribonucleotides —deoxy-adenosine 5-mono- phosphate (d AMP), deoxy guaninosine 5-monophosphate (d GMP), deoxy thymidine 5-monophosphate (d TMP) and deoxy cytidine 5-monophosphate (d CMP).

The back bone of a DNA chain or strand is built up of alternate deoxyribose and phosphoric acid groups. The phosphate group is connected to carbon 5′ of the sugar residue of its own nucleotide and carbon 3′ of the sugar residue of the next nucleotide by phosphodiester bonds. -H of phosphate and -OH of sugar are eliminated as H2O during each ester formation.

At one end of DNA strand, last sugar has its 5-C free while at other end 3-C of first sugar is free. They are respectively called 5′ and 3′ ends. Phosphate group provides acidity to the nucleic acids because at least one of its side group is free to dissociate.

Nitrogen bases lie at right angles to the longitudinal axis of DNA chains. They are attached to carbon atom 1 ‘of the sugars by glycosidic bonds. Pyrimidine is attached to deoxyribose by its N-atom at 1′ position while a purine does so by N-atom at 9’ position.

The two DNA chains are antiparallel that is, they run parallel but in opposite directions. In one chain the direction is 5′ → 3′ while in the opposite one it is 3′ → 5′ (Fig. 9.22). The two chains are held together by hydrogen bonds between their bases. Adenine (A), a purine of one chain lies exactly opposite thymine (T), a pyramidine of the other chain. Similarly, cytosine (C, a pyramidine) lies opposite guanine (G, a purine).

This allows a sort of lock and key arrangement between large sized purine and small sized pyrimidine. It is strengthened by the appearance of hydro­gen bonds between the two. Three hydrogen bonds occur between cytosine and guanine (CsG) at positions 1-1′, 2′ – 6′ and 6′ -2’.

There are two such hydrogen bonds between adenine and thymine (A=T) which are formed at positions 1’ -3′ and 6′ -4’. Hydrogen bonds occur between hydrogen of one base and oxygen or nitrogen of the other base. Since specific and different nitrogen bases occur on the two DNA chains, the latter are complementary.

Thus the sequence of say AAGCTCAG of one chain would have a complementary sequence of TTCGAGTC on the other chain. In other words, the two DNA chains are not identical. It is because of specific base pairing with a purine lying opposite a pyrimidine. This makes the two chains 2 nm thick.

A purine-purine base pair will make it thicker while a pyrimidine- pyrimidine base pair will make it narrower than 2 nm. A larger sized purine, therefore, lies opposite the smaller-sized pyrimidine, A opposite T and С opposite G. This specific base pairing makes the two chains complementary.

Sense and Antisense Strands:

Both the strands of DNA do not take part in controlling heredity and metabolism. Only one of them does so. The DNA strand which functions as template for RNA synthesis is known as template strand, minus (-) strand or antisense strand.

Its complementary strand is named non-template strand, plus (+) strand, sense or coding strand. The latter name is given because by convention DNA genetic code is written according to its sequence.

DNA Non-template, Sense (+) or Coding Strand

DNA Template, Antisense, or Noncoding or (-) Strand

(5′) G С AU U С G G С U AG U A AC (3′)

RNA is transcribed on 3′ → 5′ (-) stranu (template/anti-strand) of DNA in 5 ←3 direction. The (+) strand of DNA is that coding strand which carries genetic information but is non-template. The term antisense is also used in wider prospective for any sequence or strand of DNA (or RNA) which is complementary to mRNA.

Denaturation (= Melting):

The hydrogen bonds between the nitrogen bases of comple­mentary DNA strands can break due to high temperature, low or high pH. The phenomenon is called denaturation or melting. Since an A—T base pair has only two hydrogen bonds, the area rich in A—T base pairs can undergo easy denaturation.

It is known as low melting area. The area rich in G—С base pairs is comparatively more stable because three hydrogen bonds connect the complementary nitrogen bases. DNA strands separated by melting can re-associate and form duplex. The phenomenon is called renaturation.

Palindromic and Repetitive DNA:

DNA duplex possesses areas where sequence of nucleotides is the same but opposite in the two strands, e.g.,

These areas are called palindromes or palindromic regions. Regions connected with transcription of ribosomal RNA are often palindromic. The exact significance of this sort of arrangement is not known.

Functions of DNA:

(1) DNA is genetic material which carries all the hereditary information coded in the arrangement of its nitrogen bases.

(2) It has the property of replication (autocatalytic func­tion) essential for passing genetic information from one cell to its daughters or from one generation to the next.

(3) Crossing over produces re-combinations.

(4) Changes in sequence and number of nucleotides produce mutations. Mutations are the fountain head of all varia­tions and formation of new species.

(5) It gives rise to RNAs through transcription (Heterocatalytic function).

(6) DNA controls the metabolic reactions of cells through RNAs and RNA-directed synthesis of proteins, enzymes and other bio-chemicals.

(7) Differ­entiation of various body parts is due to differential functioning of specific parts of DNA.

(8) Developmental stages occur in the life cycle of an organism by an internal clock of DNA functioning.


Watch the video: why Thaimine instead of Uracil in DNA? or why Uracil instead of Thaimine in RNA? (January 2023).