Which characteristic would not be useful in a vector? A) A recognition sequence for a restriction enzyme B) Large size relative to the host chromosomes C) The ability to replicate independently inside the host cell D) A reporter gene E) An origin of replication

The correct answer is B) Large size relative to the host chromosomes

Explanation:

A vector for clonation or expression must contain sequence elements which allow it independent replication and identification of host cells which have incorporated the vector. Among these elements are:

- Replication origin (option E) : allows it to replicate independently of the host genome. Option B is the same as it.

- Restriction enzyme sites (option A) : in order to cut the vector and to inser the desired gene into the vector.

- Reporter gene (option E) : it allows to visualize the host cells which are expresing the inserted gene of the vector. For example, a reporter gene can codificate a fluorescent protein, thus the host cells which have expresion of the vector are fluorescent.

The only option which is unuseful is option B because if the vector has too large size, the transformation efficiency will be low. That means that fewer host cells will contain the vector after transformation.