In this section each item consists of six sentences of a passage. The first and sixth sentences are given in the beginning as S1 and S6. The middle four sentences in each have been jumbled up and labelled as P, Q, R and S. You are required to find the proper sequence of the four sentences and mark your response accordingly. S1: Mutations are random changes to the base sequence of genes. S6: Several mutations must occur in the same cell for it to become a tumour cell. P: This is why mutations in them can result in uncontrolled cell division and therefore tumour formation. Q: The few genes that can become cancer-causing after mutating are known as oncogenes. R: Most genes do not cause cancer if they mutate. S: In a normal cell oncogenes are involved in the control of cell cycle and cell division.