1
Maximum number of bases in plasmids discovered so far:
- 500 kilobases
- 5 kilobases
- 50 kilobases
- 5000 kilobases
Answer
(3) 50 kilobases
Solution
As per NCERT, plasmids are autonomously replicating circular extra-chromosomal DNA of bacteria.
∵ Plasmids used as cloning vectors are small; e.g. pBR322 has 4361 base pairs (about 4.4 kilobases).
⇒ The large natural plasmids, such as the conjugative F and R plasmids, are of the order of 50 kilobases or more.
∴ Of the given options, about 50 kilobases is taken as the maximum size of plasmids.
Answer: (3)
AIPMT 2001