Read the passage given below and answer the questions that follow : Chocoholics no longer need to feel guilty about their desire for chocolate. They are simply the victim of the genes, scientists have found. The so called "sweet-tooth gene" has been identified by separate teams of researchers and helps explain why some find it harder to resist chocolate bars and cream cakes. It also raises the possibility of designing a drug which could "switch off" the gene and help people resist sugary foods. Children, in particular, risk their health by eating too many sweets and chocolates. To identify the gene, research teams conducted almost identical experiments using mice which have differences in their ability to taste sweet foods. One of the team members said "A sweet taste receptor recognises the sweet content of food and initiates a cascade of events which signals to the brain that a sweet food has been eaten." He further added, "The same gene exists in humans, so it means that if your parents have a sweet tooth then you probably will as well". He said, "We have always known that some people have a sweeter tooth than others. But it has also been proved that if you are gradually exposed to less sugar, then the body becomes accustomed to less. They will be satisfied with a lower level of sweetness. Doctors warn against any form of gene therapy which seeks to deactivate the sweet gene. "We have produced this gene through evolution because sweet foods in nature are not poisonous, they give us energy. We all need to have some sugar in our diet," claim scientists. US researchers are using this discovery to develop artificial sweeteners without any after-taste. Identify parts of speech of the underlined words in the given sentence : 'Doctors warn against any form of gene therapy which seeks to deactivate the sweet gene'.