Many modern biotechnologies are based on our growing understanding of gene structure and function. A range of DNA-based laboratory techniques are used to study individual genes, groups of genes and whole genomes.
What is DNA
DNA (deoxyribonucleic acid) is contained in the nucleus of every cell. It is the main component of chromosomes and is the material that transfers genetic characteristics from one generation to the next.
DNA needs to be released from the cell’s nucleus before it can be analysed.
Find out more about DNA extraction and then follow up with the article Extracting ancient DNA.
DNA molecules extracted from a cell’s nucleus are very long and thin. Restriction enzymes are used to break up the DNA into fragments. These smaller fragments can then be size separated using gel electrophoresis. This is the beginning of many DNA-based experiments.
A DNA molecule actually has two strands of nucleotides that join together and wrap around each other to form a structure known as the double helix.
The sugar-phosphate-base nucleotides of DNA strands are represented by the letters G, A, T and C. Instructions or codes are ‘written’ in the sequence of the nucleotides. For example, a GATCCA sequence carries a different instruction to a GACCAT sequence.
To ‘read’ the nucleotides in the genes, scientists use a technique called DNA sequencing. During DNA sequencing, the two DNA strands are broken apart and duplicated and the nucleotides are ‘read’.
Try the activity, Modelling DNA with your class.
Making multiple copies of DNA
Once a DNA molecule has been extracted, it can be copied by DNA cloning or the polymerase chain reaction (PCR).
Generating multiple copies of DNA or of a particular gene is an important first step in many biotechnology, science and forensic applications.
Related activity idea
This activity helps students conceptualise DNA by extracting it from tomatoes.