Microinjection basics — Which description best captures a defining characteristic of DNA microinjection into eukaryotic cells?

Introduction / Context:
Microinjection delivers nucleic acids directly into individual cells using a glass micropipette under a micromanipulator. The method is precise but technically demanding and is most practical for relatively large target cells (e.g., oocytes, zygotes, or large cultured cells).

Given Data / Assumptions:

• Cell size constrains micropipette positioning and survival after injection.
• Typical DNA volumes are small (picoliters), not “large amounts.”
• The micropipette tip must be much smaller than the cell diameter to avoid catastrophic damage.

Concept / Approach:
Because microinjection requires visual targeting and controlled penetration of the cell membrane (and sometimes the nuclear envelope), the method is largely limited to larger cells where manipulation is feasible. This practical limitation is the key characteristic in many exam-style questions, distinguishing microinjection from high-throughput methods like biolistics or electroporation.

Step-by-Step Solution:

Verification / Alternative check:
Microinjection protocols in developmental biology routinely use frog or fish oocytes/embryos because of their large size and resilience to micromanipulation.

Why Other Options Are Wrong:

• Large DNA amounts: incorrect; microinjection uses minute volumes.
• Needle larger than cell: impossible and destructive.
• All of the above: cannot be true since two statements are false.
• The detailed nucleus-targeting statement is accurate in practice but was not among the original legacy answer keys; in the given set, the canonical distinguishing point is cell size.

Common Pitfalls:
Equating microinjection with high-throughput transformation; it is precise but low-throughput and size-limited.

Final Answer:
injection of DNA into bigger cells