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Question #47748
The Question
While transforming E. coli with a recombinant plasmid, a researcher must treat the cells with divalent cations (Ca2+) followed by a 42°C heat shock. However, when introducing a gene into an animal oocyte via microinjection, these chemical and thermal steps are entirely omitted. Which of the following statements correctly explains the biological basis for this methodological distinction?
Options
- A.
The hydrophilic DNA molecule can naturally diffuse across the animal cell's plasma membrane due to the absence of a rigid peptidoglycan-lipopolysaccharide barrier.
- B.
Microinjection mechanically breaches the cellular barriers to deliver DNA directly into the nucleus, bypassing the need to induce transient pores via thermal stress.
- C.
Animal cells require a much higher thermal gradient than 42°C to achieve competency, making mechanical microinjection a safer and more viable alternative.
- D.
Divalent cations facilitate DNA entry by neutralizing the negative charge of the plant cell wall, a structure that is naturally absent in animal oocytes.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Competent_Cell_Preparation|Allele_Frequency_Drift|Restriction_Endonuclease_Nomenclature
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize 'heat shock for bacteria' and 'microinjection for animals' without understanding the biophysical constraints.
The primary trap (Option A) exploits the misconception that animal cells are naturally permeable to DNA simply because they lack a cell wall, ignoring the fundamental NCERT fact that DNA is hydrophilic and cannot cross the hydrophobic plasma membrane without either induced pores (heat shock) or mechanical breach (microinjection).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology : Principles and Processes - Class 12 |
| Concept | Competent Cell Preparation |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |