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DNA structure

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The 3D structure of DNA

Deoxyribonucleic acid (DNA) is often called the blueprint for life. This is because all the information required to build a functioning organism is contained within the DNA. All living cells contain DNA at some stage in their lifespan.

Different types of organisms have different DNA the DNA of a bacterial cell is different to the DNA found inside your own cells. However, your DNA still has a lot in common with the DNA of bacteria and even with that of a tree.

The nucleotide

DNA is a type of nucleic acids, one of the main biomolecules. Like all other biomolecules, DNA is a polymer made from a large number of subunits joined together. The subunits, or monomers, are called nucleotides. (See the Biological macromolecules chapter from the MUF0031 eBook, Cell Biology)

A DNA nucleotide is made up of three components:

deoxyribose a 5-carbon sugar molecule (carbohydrate)

phosphate group and a

nitrogen base or nitrogenous base.

Figure 1: A DNA nucleotide is made up of a phosphate group and a deoxyribose sugar molecule attached to one of four different nitrogen bases.

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The carbon atoms in the sugar molecule are numbered 1 to 5. The phosphate group bonds to the deoxyribose sugar at the 5’ (five prime) carbon of the sugar. One of four different nitrogen bases is also attached to the sugar molecule, but at the 1’ (one prime) carbon.

Nitrogen bases are classed into two groups.