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What is DNA? – Definition, Structure, Types, Functions

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  • Last Updated : 13 Jul, 2022
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DNA(Deoxyribonucleic Acid)), which represents deoxyribonucleic acid, is a particle that provisions the hereditary guidelines that advise living animals on how to grow, live and replicate. DNA can be tracked down inside each cell and is passed down from guardians to their posterity. DNA is comprised of particles called nucleotides. Every nucleotide contains three parts: a phosphate bunch, which is one phosphorus bond to four oxygen particles; a sugar atom; and a nitrogen base. The four sorts of nitrogen bases are adenine (A), thymine (T), guanine (G), and cytosine (C), and together, these act as the “letters” that make up the hereditary code of our DNA.

Nucleotides are joined together to frame two long strands that twist to make a construction called a twofold helix. On the off chance that you consider the twofold helix structure as a stepping stool, the phosphate and sugar particles would be the sides, while the base matches would be the rungs. The bases on one strand pair with the bases on another strand: Adenine matches with thymine (A-T), and guanine matches with cytosine (G-C).



Most chromosomes seem to be minute Xs; all things considered, people and most different warm-blooded creatures convey a couple of sex chromosomes that can be either X or Y-formed, as per the National Human Genome Research Institute. As a general rule, females convey two X sex chromosomes in each body cell and guys convey one X and one Y. Yet, there is some regular variety in the number of sex chromosomes individuals convey — in some cases, there might be additional sex chromosomes, or one may be missing, so different examples, like X, XXX, XXY and XXYY.

The human quality HBA1, for instance, contains directions for building the protein alpha globin, which is a part of hemoglobin, the oxygen-conveying protein in red platelets, as per the NLM(opens in new tab). To take another model, the quality OR6A2 encodes an olfactory receptor, a protein that recognizes scents in the nose, as per the National Center for Biotechnology Information’s Gene database(opens in new tab). Contingent upon which adaptation of OR6A2 you have, you might cherish cilantro or think it has an aftertaste like cleanser.

Albeit every single one of your 37.2 trillion cells conveys a duplicate of your DNA, not all cells fabricate similar proteins. One justification behind this is that atoms called “record factors” hook onto DNA to control which qualities get turned on and off, and hence, which proteins get made when, where and in what amounts in every phone. DNA additionally gets bundled somewhat distinctively in various cell types, and this impacts how and where record variables can take hold of the particle.

Structure of DNA

The DNA construction can be considered a turned stepping stool. This design is depicted as a twofold helix, as delineated in the figure above. It is a nucleic corrosive, and all nucleic acids are comprised of nucleotides. The DNA atom is made out of units called nucleotides, and every nucleotide is made out of three unique parts, for example, sugar, phosphate gatherings, and nitrogen bases.

The fundamental structure blocks of DNA are nucleotides, which are made out of a sugar bunch, a phosphate bunch, and a nitrogen base. The sugar and phosphate assemblies connect the nucleotides to shape each strand of DNA. Adenine (A), Thymine (T), Guanine (G), and Cytosine (C) are four kinds of nitrogen bases.

These 4 Nitrogenous bases pair together in an accompanying manner: A with T and C with G. These base sets are fundamental for the DNA’s twofold helix structure, which looks like a wound stepping stool.

The two strands of DNA run in inverse headings. These strands are kept intact by the hydrogen bond that is available between the two corresponding bases. The strands are helically bent, where each strand frames a right-given curl, and ten nucleotides make up a solitary turn.

The pitch of every helix is 3.4 nm. Subsequently, the distance between two back-to-back base matches (i.e., hydrogen-fortified bases of the contrary strands) is 0.34 nm.

Types of DNA

There are two kinds of DNA autosomal DNA and mitochondrial DNA.

Autosomal DNA 

Nuclear DNA (nuclear DNA) is available in the cell core of eukaryotic organic entities and procured from the two guardians. The construction of atomic DNA is made out of 46 chromosomes, of which 23 are from the dad and the other 23 from the mother.

Mitochondrial DNA: 

Mitochondrial DNA is available in the mitochondria, and every cell contains around 100-1000 duplicates. Mitochondrial DNA is haploid, meaning it comes from one source, which is the mother. This kind of DNA has a higher transformation rate than atomic DNA.



This seems when the natural stickiness is under 75% and is seldom present under ordinary physiological circumstances. The twofold strands are antiparallel and shaped by sugar phosphates utilizing phosphodiester bonds. Infections adjust this type of DNA as a versatile method of endurance in cruel natural circumstances.


Discovered in view of X-beam diffraction designs and existed under typical physiological circumstances. Twofold strands of B-DNA run in inverse headings, and the two strands are kept intact by hydrogen connections between the base units.


This is the structure DNA takes when exposed to somewhat low dampness and explicit particles like Li+ and Mg2+. This structure is shaky and doesn’t happen normally in living organic entities. Both B and C-DNA contain comparable nucleotide adaptations however at various proportions.


Lacks the Guanine (G) base unit making it an interesting variation. This type of DNA structures under lower mugginess than A-DNA.


 Is a lengthy or unusual organismal DNA present in the climate? E-DNA is from cell material shed by various organic entities into the climate like skin, mucous, discharged feces, hair, gametes, and corpses. The DNA goes on around 7-21 days, contingent upon natural circumstances like openness to acridity, intensity, or radiation.


Stands out with its crisscross appearance. It comprises of minor and significant sections as it’s a left-given twofold helix. This type of DNA is available in eukaryotes, microscopic organisms, and infections. In light of ongoing examinations, Z-DNA connects to sicknesses like Alzheimer’s and Systemic lupus erythematosus through the presence of normally happening antibodies.

Function of DNA

DNA is the hereditary material that car­ries all the inherited data. Qualities are the little sections of DNA, comprising generally 250 – 2 million base matches. A quality code for a polypeptide particle, where three nitrogenous bases succession represents one amino corrosive.

Polypeptide chains are additionally collapsed in optional, tertiary, and quaternary designs to shape various proteins. As each creature contains numerous qualities in its DNA, various sorts of proteins can be framed. Proteins are the primary useful and underlying particles in many life forms. Aside from putting away hereditary data, DNA is engaged with:

  • Replication process: Transferring the hereditary data from one cell to its little girls and starting with one age then onto the next and equivalent dispersion of DNA during the
  • Cell division
  • Transformations: The progressions which happen in the DNA groupings.
  • Cell Metabolism
  • DNA Fingerprinting
  • Quality Therapy.

Properties of DNA 

  • Right-gave or left-gave DNA helices exist. In any case, the right-given helices of the B – conformity of DNA are the most steady.
  • At the point when two strands of DNA are warmed, they discrete and afterward re-hybridize when they are cooled.
  • Liquefying temperature is characterized as the temperature at which the two strands separate totally (Tm). For each arrangement, the softening temperature is unique.
  • Since the C-G pair has three hydrogen bonds, the B test of DNA with a higher dissolving point should have more C-G.
  • Each protein in all species has a succession of amino acids that is encoded by the base grouping along with the DNA particle.

Difference between RNA and DNA 

  • DNA contains the sugar deoxyribose, while RNA contains the sugar ribose. The main distinction between ribose and deoxyribose is that ribose has one more – OH bunch than deoxyribose, which has – H appended to the second carbon in the ring.
  • DNA is a twofold abandoned particle, while RNA is a solitary abandoned particle.
  • DNA is steady under antacid circumstances, while RNA isn’t steady.
  • DNA and RNA carry out various roles in people. DNA is liable for putting away and moving hereditary data, while RNA straightforwardly codes for amino acids and goes about as a courier among DNA and ribosomes to make proteins.
  • DNA and RNA base matching is marginally unique since DNA utilizes the bases adenine, thymine, cytosine, and guanine; RNA utilizes adenine, uracil, cytosine, and guanine. Uracil contrasts from thymine in that it comes up short on methyl bunch on its ring.

DNA stronger than RNA 

Both DNA and RNA contain the sugar ribose, which is basically a ring of carbon molecules encompassed by oxygen and hydrogen. In any case, though RNA contains a total ribose sugar, DNA contains a ribose sugar that has lost one oxygen and one hydrogen particle. Fun truth: This minor contrast makes sense of the various names appointed to RNA and DNA – ribonucleic corrosive versus deoxyribonucleic corrosive. The additional oxygen and hydrogen iotas in RNA leave it inclined to hydrolysis, a substance response that successfully breaks the RNA particle fifty. Under ordinary cell conditions, RNA goes through hydrolysis very nearly multiple times quicker than DNA, which makes DNA a more steady particle. DNA is stronger than RNA because 

  • DNA is more easily repaired.
  • DNA Information is more protected.
  • Double strands and allow double-checking.

Importance of DNA 

DNA contains the guidelines that are fundamental for a living being to develop, create, and repeat. These directions exist inside the grouping of nucleotide base matches.

DNA assists your body with developing
Your cells read this code on three bases all at once to create proteins that are fundamental for development and endurance. The DNA grouping that houses the data to make a protein is known as quality.

Each gathering of three bases compares to explicit amino acids, which are the structure blocks of proteins. For instance, the base matches T G indicates the amino corrosive tryptophan, while the base matches G-C determines the amino corrosive glycine.

A few mixes, similar to T A, T-A-G, and T-G-A, likewise show the finish of a protein succession. This tells the cell not to add more amino acids to the protein.

Proteins contain various mixes of amino acids. At the point when put in together in the right request, every protein includes a special construction and capability inside your body

Conceptual Questions

Question 1:  What is the composition of DNA? 


DNA is made of synthetic structure blocks called nucleotides. These structure blocks are made of three sections: a phosphate bunch, a sugar gathering, and one of four kinds of nitrogen bases. To shape a strand of DNA, nucleotides are connected into chains, with the phosphate and sugar bunches substituting. The four kinds of nitrogen bases found in nucleotides are adenine (A), thymine (T), guanine (G), and cytosine (C). The request, or grouping, of these bases, figures out what natural guidelines are contained in a strand of DNA. For instance, the arrangement could educate for blue eyes, while it could train for brown. The total DNA guidance book, or genome, for a human, contains around 3 billion bases and around 20,000 qualities on 23 sets of chromosomes.

Question 2: What are the three unique kinds of DNA?


There are three distinct DNA types:

  • A-DNA: It is a right-given twofold helix like the B-DNA structure. Got dried out DNA takes A structure that safeguards the DNA during outrageous circumstances like drying up. Protein restricting likewise eliminates the dissolvable from DNA, and the DNA takes A structure.
  • B-DNA: This is the most well-known DNA compliance and is a right-given helix. Most DNA has B-type compliance under typical physiological circumstances.
  • Z-DNA: Z-DNA is a left-given DNA where the twofold helix winds to one side in a crisscross example. It was found by Andres Wang and Alexander Rich. It is viewed as in front of the beginning site of quality and subsequently, is accepted to assume some part in quality guidelines.

Question 3: What is the function of DNA in the human body?


DNA is the base genetic information molecule of a cell. It will pass the information from generation to generation. It keeps the information intact.

  • Genetic information
  • Help in mutation
  • Cellular Metabolism
  • Translation of essential protein for proper functioning

Question 4: Differentiate between DNA and RNA?


The DNA is stronger than the RNA because in DNA deoxyribose is used whereas in RNA ribose sugar is used, so because of the sugar the Tm of DNA is high and it’s not easily broken down whereas RNA can and its Tm is also low.

Question 5: What are the properties of DNA?


  • DNA helices can be correct given or left given. Yet, the B – conformity of DNA having the right given helices is the most steady.
  • On warming the two strands of DNA separate from one another and on cooling these again hybridize. The temperature at which the two strands separate totally is known as dissolving temperature (Tm). Softening temperature is explicit for every particular arrangement.
  • The B test of DNA having a higher dissolving point should have more C-G content since C-G pair has 3 hydrogen bonds.
  • The succession of bases along the DNA particle encodes for the grouping of amino acids in each protein in all creatures.

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