Which task becomes difficult in gene cloning without a cloning vector?

Correct answer: Carrying desired DNA into host

The direct answer is A: carrying desired DNA into the host. Gene cloning requires a DNA fragment to enter a suitable host cell and usually to be copied there. A cloning vector acts like a biological vehicle: the desired gene is inserted into it, the recombinant vector is introduced into the host, and the vector’s features help the DNA remain or replicate. Thus, without a vector, carrying the desired DNA into the host and obtaining many copies becomes difficult in the context of this question. A is correct. B, digesting protein, is an enzymatic activity and is not the main role of a cloning vector. C, freezing water, is a physical process unrelated to gene cloning. D, colouring fat, is also unrelated and does not help DNA transfer. Some DNA can enter cells by other methods, so “without a vector” does not mean transfer is absolutely impossible in every technology; it means the normal vector-based cloning task is made difficult. Exam cue: vector means a vehicle for the gene.