Q.45 Which of the following vector(s) is(are) used to clone a DNA fragment of size
220 kb?
(A) Bacterial artificial chromosome
(B) Yeast artificial chromosome
(C) Cosmids
(D) pUC19 plasmid
Cloning vectors like BAC and YAC enable handling large DNA inserts up to 220 kb, unlike smaller-capacity options. This guide details each vector’s capacity for precise exam prep.
Option Analysis
Bacterial artificial chromosome (BAC) accommodates 100-350 kb inserts, making it ideal for 220 kb fragments in stable bacterial cloning. Yeast artificial chromosome (YAC) handles 100-1000 kb, perfect for very large eukaryotic DNA libraries including 220 kb. Cosmids limit to 35-52 kb due to lambda phage packaging constraints, insufficient for 220 kb. pUC19 plasmid caps at 10-15 kb, suited only for small inserts via high-copy E. coli replication.
Correct Answer
Options (A) and (B) work for 220 kb DNA. BAC offers low-chimerism stability; YAC excels in genomic mapping despite instability risks.
Vector Comparison Table
| Vector | Insert Size Capacity | Best Use Case |
|---|---|---|
| BAC (A) | 100-350 kb | Large stable bacterial clones |
| YAC (B) | 100-1000 kb | Eukaryotic genomic libraries |
| Cosmids (C) | 35-52 kb | Medium genomic libraries |
| pUC19 (D) | Up to 15 kb | Small gene cloning |
