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gsenviro eNotes educator| Certified Educator

DNA or Deoxyribonucleic acid is a double-stranded helical molecule and codes the genetic information necessary for life. Each DNA molecule consists of four nitrogen containing nucleobases: 

Adenine (designated as A)

Guanine (designated as G)

Thymine (designated as T) and,

Cytosine (designated as C).

Of these four bases, A and G are Purines, and are five and six-membered heterocyclic compounds. The remaining bases, C and T are known as Pyrimidines, and have six-membered ring structures.

The double-helix structure of DNA is possible only because of complementary base pairing, in which one base on a strand will only pair with a specific base on the other strand, through hydrogen bonds. For example, adenine pair with thymine through two hydrogen bonds and cytosine only pairs with guanine through three hydrogen bonds. The complementary pairing of nucleobases enables the DNA replication and is crucial for life.

There is another nucleobase, Uracil (designated as U) that is present only in RNA and replaces thymine. 

Hope this helps.

Nolan McShea | Student

The four bases in DNA are thymine, cytosine, guanine, and adenine. You can represent these four bases with letters: T,C,G,A.

Two of these nitrogenous bases, thymine and cytosine, are pyrimidines, which consist of one hexagonal shape. You can see this in the picture I've attached below. You may disregard the Uracil (U) in the picture, though. In case you're curious, Uracil only appears in RNA and replaces thymine (T). 

The other two nitrogenous bases, guanine and adenine, are purines, which consist of a hexagonal shape with a pentagon attached. You can see these, as well, in the image I've attached.

You must always remember this:



These are the laws of the complementary bases in DNA. They always, ALWAYS connect. An easy way to remember this is that C looks like G. Once you've got that, all that's left is A and T, so you can remember that.

Example: Get the complementary strand of CGGCGTCGCATC

Convert all of them, and you should get GCCGCAGCGTAG.

I hope I helped!

Fun fact: DNA is grouped into codons. Codons are groups of 3 complementary bases.

punitjoshi369 | Student

DNA is Deoxyribonucleic acid. It is a nucleic acid . It has nitrogen containing  bases. The four bases are: 

A- Adenine

C- Cytosine

G- Guanine

T- Thymine

These bases gets combined as per base -pair rule. Adenine (A) gets combined with Thymine (T) and Cytosine (C) b gets combined with Guanine (G).

ramanlady | Student

Adenine, Thymine, Cytosine, Guanine

iamkaori | Student

The four nitrogenous bases in DNA are adenine, guanine, cytosine, and thymine. Adenine and guanine are larger purines compared to cytosine and thymine. Cytosine usually pairs up together with guanine, and adenine pairs up together with thymine. Each base has a distinct shape that makes it impossible to have them pair with another base other than the one they can pair with.

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