Question

Plasmids were discovered by
A. Hayes and Lederberg
B. Lederberg and Tatum
C. Bolivar and Rodriguez
D. Messing and Vieria

Answer 1

A plasmid is a small, extra-chromosomal DNA molecule. They are commonly found as small circular, double-stranded DNA molecules in bacteria. There are various shapes of plasmids but circular is a common structure. Linear plasmids are also well known. Plasmids may be present in an individual cell in numbers ranging from one to several hundreds. Plasmids have greater advantages.

Complete answer:
Option A Hayes and Lederberg: Hayes and Joshua Lederberg are the scientists which first discovered plasmids in $1953$. They observed it in salmonella bacteria. Then later he named it as an extrachromosomal hereditary element.
Option A is correct.
Option B Lederberg and Tatum: Lederberg discovered the plasmid that is true but Tatum along with Lederberg is not the correct option hence, it is incorrect.
Option B is not correct.
Option C Bolivar and Rodriguez: they discovered the vector. Vectors are known to be the carrier of certain components. They first observed the $pBR322$ vector.
Option C is not correct.
Option D Messing and Vieria: messing and Vieria also usually, named in the pages of the discoveries of vectors.
Option D is not correct.

Hence, Option A is the correct answer.

Note:
As we already know the advantages and disadvantages of plasmid, even who discovered the plasmid. Bacteria are classified on the basis of morphology. The spherical shape is called coccus, rod shaped bacilli, spiral spirillum. Plasmids are found in bacteria bodies and they perform resistance in them. Plasmid lies in other eukaryotic organisms too. It is a great tool in recombinant DNA technology. Used in various experiments as it has the resistance power against any diseases.