Science In The Pub Adelaide

Synthetic DNA

Synthetic genes can be built to be responsive to different inductive stimuli like antibiotics, food supplements like flavourings, amino acids, and vitamins, medications and drugs, lotion-based chemicals that can penetrate the skin, redox and hormones state, endogenous metabolites, physical stimuli, etc.

The process of gene synthesis can be described as the construction and assembly of genes from nucleotides de novo. Artificial synthesis, unlike living cells DNA synthesis, does not need any template DNA. This means that any DNA sequence can be synthesised in the laboratory. All it takes to do is just two necessary steps. The first is the solid-phase DNA synthesis which is also called DNA printing. It creates the oligonucleotide fragments. The second stage connects the oligonucleotide fragments through several methods for assembling DNA. Theoretically, it is possible to create a DNA molecule that is entirely synthetic without any limit in the size and sequence of the nucleotide.

Oligonucleotide synthesis

In this method, there is a chemical synthesis of the oligonucleotide with building blocks that are known as nucleoside phosphoramidites. They can be modified or regular nucleosides that have to protect groups to ensure that their amines, phosphate groups, and hydroxyl groups do not interact incorrectly. In this process, the addition of phosphoramidite is one at a time, and there is deprotection of the 5′ hydroxyl group during the addition of a new base. While this process seeks to achieve the perfect results, the fact that it is a chemical process makes it prone to various incorrect interactions which leads to defective products. The length of the oligonucleotide sequence being synthesised will determine how effective it is. Thus, this method is best for making short sequences. At the moment, the limit is around 200 base pairs for oligonucleotide with a quality that is good enough to be utilised directly for biological application.

Annealing based connection of oligonucleotides

In this method, the sets of oligonucleotides are individually designed with automated solid-phase synthesisers and then purified and connected using specific annealing and normal polymerase and ligation reactions. In order to enhance the specificity of the annealing, the synthesis stage uses thermostable DNA polymerase and ligase enzymes. This method usually uses oligonucleotides that are about 40-50 nucleotides long and overlaps each other. The oligonucleotides are fashioned to cover most of both strands sequences. Overlap extension is used to generate full-length molecules progressively.

Limitations

Because assembling gene products that are full length requires specific and efficient alignment of the single-stranded oligonucleotides, crucial parameters are put in place for synthesis success. The outcome of any gene synthesis will be determined by the quality of oligonucleotides.

Benefits

Scientists can now synthesise and design bacterial chromosomes which can be used to produce bioproducts, advanced biofuels, renewable chemicals, and lots more.