EXPLANATION/ANSWER:
Through genetic engineering, tomatoes gained a gene called polygalacturonase in its antisense DNA strand that when the antisense strand is expressed, it prevents them from softening by interfering to the production of the enzyme polygalacturonase enzyme. Other scientists have developed a tomato with inhibited ethylene production and by doing so, the tomato delayed ripening. To make this, they inserted a modified version of the ACC synthase gene into the tomato DNA. This gene came from Pseudomonas chlororaphis.