Q.74 Bacterial artificial chromosomes (BAC) are capable of cloning fragments upto
- 500–750 kb
- 200–250 kb
- 50–150 kb
- 300–350 kb
Bacterial artificial chromosomes (BACs) are engineered vectors based on the F-plasmid, capable of stably cloning large DNA fragments typically up to 300–350 kb, making option D correct.
BAC Cloning Capacity
BACs excel in genomic libraries due to their low-copy replication, which maintains stability for inserts of 100–350 kb without chimerism or rearrangement issues seen in smaller vectors. This range suits whole-gene cloning including regulatory elements, unlike YACs (up to 1000 kb but unstable).
Option Breakdown
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500–750 kb (Incorrect): Exceeds standard BAC limits; approaches YAC territory but BACs rarely achieve this stably.
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200–250 kb (Incorrect): Underestimates BAC capacity; typical lower end is 100–150 kb, averaging higher.
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50–150 kb (Incorrect): Matches cosmids or lambda phages, not BACs which handle 2–5x larger inserts.
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300–350 kb (Correct): Precise upper limit for BACs in E. coli, confirmed across genome projects.
Bacterial artificial chromosomes (BAC) revolutionized genomics with their BAC cloning capacity of 300–350 kb, ideal for stable large-fragment cloning in E. coli. This bacterial artificial chromosomes BAC cloning fragments kb guide cracks NEET/GATE questions on vector capacities versus plasmids (15 kb), cosmids (45 kb), or YACs (1000 kb).
Key Features of BACs
BACs use F-plasmid origins for single-copy maintenance, enabling bacterial artificial chromosome cloning capacity up to 350 kb without deletions—crucial for human genome sequencing. Unlike phages, they avoid packaging limits; unlike YACs, they resist chimerism.
Option Capacity Range Vector Match Why Wrong/Correct A 500–750 kb YAC upper end Too large for BAC stability B 200–250 kb BAC average Understates max capacity C 50–150 kb Cosmids/phages Far below BAC range D 300–350 kb BACs Exact standard limit NEET Exam Insights
Bacterial artificial chromosomes (BAC) cloning capacity kb questions test vector hierarchies: plasmids < phages < cosmids < BACs < YACs. Focus on BAC’s 300–350 kb for large eukaryotic genes in biotech exams. Practice with insert size comparisons for mastery.
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