SV40 genome basics: What is the approximate size of the Simian Virus 40 (SV40) genome?

Introduction / Context:
SV40 is a classic small DNA virus used in molecular biology as a model for eukaryotic replication and as the source of powerful regulatory elements (e.g., SV40 promoter). Knowing its genome size is foundational knowledge for vector design and literature comprehension.

Given Data / Assumptions:

• Genome size is requested in kilobases (kb).
• SV40 is a small, circular, double-stranded DNA virus.

Concept / Approach:
The SV40 genome is approximately 5.2 kilobases in length (about 5,243 base pairs). This compact genome encodes early and late genes and regulatory elements widely adapted for expression constructs. Larger sizes listed in the distractors correspond to entirely different viral systems or are unrealistic for SV40.

Step-by-Step Solution:

Verification / Alternative check:
Genome maps and reference sequences consistently report ~5.2 kb for SV40, validating the answer.

Why Other Options Are Wrong:

• 7.2 kb: too large for SV40; closer to some other small viral genomes.
• 69 kb, 110 kb: sizes more typical of large DNA viruses, not SV40.
• 2.6 kb: too small to encode SV40 functions.

Common Pitfalls:
Confusing SV40 with adenovirus or herpesvirus sizes; those are much larger.

Final Answer:
5.2 kb