Practice question

Question

As depicted in the figure below, the sequence of trypanosomal mitochondrial cytochrome oxidase subunit II (COX 11) mRNA does not match the sequence of the COX II gene. The mRNA contains four additional U's (highlighted) which are not represented by 'T's in the gene, and these four U's are presumably added to the RNA by editing COX II DNA: ... GT AT MAAGT AGA G A ACCTGG··· COX II RNA: ···GUAUMAAGUAGAUUGUAUACCUGG··· The following statements were made about RNA editing: A. RNA editing can add or remove U's from the target mRNA. B. Editing occurs in the 5' - 3' direction by successive action of one or more guide RNAs. C. A terminal uridylyl transferase (TUTase) facilitates addition of extra UMPs (urldylates) to the mRNA during editing. D. The proteins required for editing are encoded by the mitochondrial DNA, while the required guide RNAs are encoded in the nucleus and imported into the mitochondria. Which one of the following options shows the combination of all correct statements?