Patenting depends on invention, so the patenting of a synthetic gene would need to emphasize the newness, the inventedness of gene to increase lipid production in microalgae. Such invention could include the fusion of gene parts not normally found together in nature, editing of gene sequences, alteration of regulatory elements (promoter, enhancers), and similar operations.
Work Step by Step
The key here is to see in the text that patents are only given for invention. Then go through the ways that biotechnologists and list those which could be used to improve the gene and mention how each "invents" something new about the gene, something not found in nature.