Foot-and-mouth disease virus (FMDV) genome size — Approximately how many nucleotides are present in the single-stranded RNA (ssRNA) molecule of this picornavirus?

Introduction / Context:
Picornaviruses possess positive-sense, single-stranded RNA genomes that function directly as mRNA upon entry. Knowing typical genome sizes helps in designing RT-PCR assays, sequencing strategies, and understanding coding capacity (single large polyprotein strategy). Foot-and-mouth disease virus (FMDV) is a classic member of this family affecting cloven-hoofed animals.

Given Data / Assumptions:

• The genome is single-stranded, positive-sense RNA.
• It encodes one large polyprotein that is post-translationally cleaved.
• Typical picornavirus genomes fall in the ~7,000–9,000 nucleotide range.

Concept / Approach:
Recall the canonical size range and select the closest representative value. FMDV genomes are about 8 to 8.5 kilobases in length. Therefore, the best rounded option among those provided is 8,000 nucleotides.

Step-by-Step Solution:

Verification / Alternative check:
Reference genomes of various FMDV serotypes consistently report ~8.2–8.5 kb, validating that 8,000 is the closest rounded choice here.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing “kb” (kilobases) with “kDa” (kilodaltons) or mixing up DNA vs RNA viruses with larger genomes.

Final Answer:
8,000.