Lately, it was discovered that people who carry the sickle-cell trait heterozygously are resistant to malaria. how could biotechnology best use this infomation to people living in these areas?

Insertion of malaria resistant gene in the human population living in the areas with malaria outbreak.

Explanation:

The heterozygous genotype for sickle cell trait is resistant to malaria. Insertion of one copy of sickle cell allele in individuals could impart them resistance to malaria. Biotechnological methods of introduction of gene into a host organism could be applied to create heterozygous genotype which in turn would protect these genetically modified humans against malaria.