Long strands of DNA consist of alternating sugar and phosphate sections. Attached to each sugar is one of four bases — A. C. G or T. Each unit of a sugar, phosphate, and base is known as a nucleotide.
A sequence of three bases is the code for an amino acid.
The order of bases controls the order in which amino acids are assembled to produce a particular protein.
In the complementary strands of DNA, a C is always linked with a G on the opposite strand, and a T to an A.
Proteins are synthesized according to a template. Carrier molecules bring specific amino acids to add to the growing protein chain in the correct order.
When the protein chain is complete it folds up to form a unique shape that enables the protein to carry out its function in the cell.
Not all parts of the DNA code for proteins. Non-coding parts switch genes on or off, so variations in these areas of DNA can affect how genes are expressed.
A change in the DNA structure may result in a change in the protein synthesized by the gene.
Mutations occur continuously Most do not alter the protein, or they alter it so slightly that the function is not affected.
A few mutations code for an altered protein with a different shape. affecting the function. This may be an advantage or a disadvantage.