DNA – Double helix

DNA has a double helix structure which looks like this:

(Note: The image below depicts a left handed helix, which is very rare in nature, but does occur)

Image of the DNA double helix

Sections of DNA called genes control the development of characteristics such as height, eye colour and hair colour.

Sections of DNA are called genes that control characteristic development.

If we look at a section of DNA in more detail we can see this is made up of nucleotides

Annotated magnification of DNA showing its structure like rungs on a ladder

Each nucleotide contains three parts:

A phosphate

A sugar

And a base

Simple contense diagram of a nucleotide these give DNA structure

The phosphate and sugar form the upright of the DNA strand and the bases make up the rungs of the ladder

Close up diagram showing how a nucleotide possitions into the double helix through strong hydrogen bonds

This can be shown diagrammatically as:

Simplified structure of DNA nitrogenous bases and hydrogen bonds between bases

Or more simply shown as

Further simplification of the hydrogen bonds of nitrogenous bases

There are four bases found within DNA, these are:

Thymine (T)

Adenine (A)

Cytosine (C)

Guanine (G)

These join up in pairs within the DNA

There are four bases of nucleotides these are Thymine, Adenine, Cytosine, Guanine

Adenine (A) can only join to thymine (T)

And cytosine (C) can only join to guanine (G)