what is structure of DNA

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sanjeetmanna's profile pic

sanjeetmanna | College Teacher | (Level 3) Assistant Educator

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DNA stands for Deoxyribonucleic acid.

DNA is the genetic material of the cell.

Watson and Crick model is considered as the best model to describe the structure of the DNA.

It is the polynucleotic acid chain of deoxynucleotides they are dNMP in 5'→3' phosphodiester linkage.

The nucleotides are twisted around each other and form the double helix structure. 

It consists of two stands which are twisted around each other with a specific angle. The two stands are complementary to each other.

The nucleotides in each stand is bound by phosphodiester bonds and the two stands are bound with the hydrogen bonds with the complementary nucleotide on both the stands(A is bound by double with T and C is bound by triple bond with G).

Note:- the stand are in anti parallel manner

We can assume the twisted ladder structure the rungs of the ladder are the base pairs that is A=T and C≡G, and the sides of the ladder are the sugar-phosphate-nitrogenbase backbone of the stand.

The DNA formes the chromosome which is located in the nucleus of the cell.

The nitrogen bases are A, T, G and C

A nucleoside is nitrogen base + sugar(ribose sugar).

Nucleotide is phosphate + nucleoside.

and when we remove a oxygen from phosphate in the nucleotide they for deoxynucleotide or deoxyribonucleoside.

Deoxyribonucleoside joined together by phosphodiester bond to form a single stand.

the nucleotides are joined by hydrogen bond forming basepairs.

NOTE :- its a complex model refer watson and crick model for mode details.

trophyhunter1's profile pic

trophyhunter1 | College Teacher | (Level 1) Educator Emeritus

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Deoxyribonucleic acid, or DNA is a double-stranded molecule in the shape of a double helix. It resembles a ladder twisted every few rungs or a spiral staircase. Its makes up the chromosomes and genes and stores the genetic code of organisms. DNA is made of subunits called nucleotides. A nucleotide consists of a phosphate group, a sugar called deoxyribose and one of four nitrogenous bases--adenine, thymine, guanine and cytosine. The sugar and phophate group make up the sides of the ladder and the rungs of the ladder are the nitrogenous bases. There are two nucleotides on each level of the DNA ladder because of its double-stranded nature. The nitrogenous bases bond in the center and are held together by weak hydrogen bonds. They pair by specific rules--adenine pairs with thymine and cytosine pairs with guanine. If you picture a zipper that is closed, the sides of the zipper are the phophate group and the sugar and the teeth that join together would be the base pairs.

francy17's profile pic

francy17 | Student, Grade 11 | (Level 1) Salutatorian

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The structure of DNA is illustrated by a right handed double helix, with about 10 nucleotide pairs per helical turn. Each spiral strand, composed of a sugar phosphate backbone and attached bases, is connected to a complementary strand by hydrogen bonding (non- covalent) between paired bases, adenine with thymine  and guanine with cytosine .

Adenine and thymine are connected by two hydrogen bonds (non-covalent) while guanine and cytosine are connected by three.


Excellent resource below:


 The illistrations really help you to grasp it...


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