Minimal gene set: Current estimates place the minimum set of genes required for cellular life in what approximate range (considering free-living but streamlined organisms)?

Introduction / Context:
Determining a minimal gene set illuminates which functions are absolutely essential for a cell to grow and divide. Studies in Mycoplasma and synthetic minimal cells combine comparative genomics and targeted gene knockouts to estimate this lower bound.

Given Data / Assumptions:

• Focus on the minimal set compatible with autonomous growth in rich media.
• Obligate symbionts may have fewer genes but rely on hosts; the question targets self-replicating minimal cells.
• We choose a gene count range consistent with experimental evidence.

Concept / Approach:

Genome minimization and transposon mutagenesis identify genes essential for DNA replication, transcription/translation, membrane integrity, metabolism, and cell division. Work with Mycoplasma genitalium and synthetic JCVI minimal cells suggests roughly 300 genes (on the order of 250–350) suffice under laboratory conditions.

Step-by-Step Solution:

Verification / Alternative check:

Synthetic biology efforts reconstructed minimal genomes having roughly 473 genes (including quasi-essential), with estimates for strict essentials near the low-300s; older estimates for M. genitalium essentials are also in this ballpark.

Why Other Options Are Wrong:

50–100: insufficient for a functioning translational and replication system.

1000–2000: represents typical bacteria, not minimal.

Common Pitfalls:

Confusing minimal free-living cells with obligate symbionts that outsource many functions to hosts; the latter can have very small genomes but are not autonomous.

Final Answer:

250–350 genes