Given below are a few terms related to map-based sequencing of genomes:

A. Partial digestion with restriction enzymes.
B. Assembly of contigs
C. Pulsed field gel electrophoresis
D. Cloning in cosmids/YACs/BACs
E. Sub-cloning and sequencing

Which one of the following options represents the correct order of steps (based on the above terms) in map-based sequencing?

Correct option is B

Explanation-

1.  C. Pulsed Field Gel Electrophoresis (PFGE)
     PFGE is used early to separate large fragments of genomic DNA and estimate their size. This helps select appropriate fragments for mapping and cloning.
2.   A. Partial Digestion with Restriction Enzymes
     Partial digestion of genomic DNA creates overlapping large DNA fragments. These are the input for large-insert clone libraries.
3.   D. Cloning in cosmids/YACs/BACs
     The large fragments are cloned into vectors (like BACs) to construct a physical map.
4.   B. Assembly of contigs
      By fingerprinting and overlapping clone ends, contigs (continuous sequences) are assembled.
5.   E. Sub-cloning and sequencing
      Finally, selected clones are broken down, sub-cloned, and sequenced in detail.

Final  Order:
C → A → D → B → E
Which matches: Option b
​