In PCR, Acquaticus thermophilus is preferred over E.coli because: (PGI Dec 2007)
**Core Concept**
The question is based on the principle of **Polymerase Chain Reaction (PCR)**, a technique used in molecular biology to amplify a single copy or a few copies of a segment of DNA across several orders of magnitude. **Thermophilic enzymes**, such as those derived from **Aquaticus thermophilus (now known as Thermus aquaticus)**, are crucial for this process due to their thermostability.
**Why the Correct Answer is Right**
**Thermus aquaticus** is preferred over **E. coli** because its DNA polymerase, known as **Taq polymerase**, is stable at high temperatures. This thermostability allows **Taq polymerase** to withstand the repeated cycles of heating and cooling inherent in the PCR process, making it an ideal enzyme for DNA amplification.
**Why Each Wrong Option is Incorrect**
**Option A:** Not provided, assuming it's about the source or another incorrect reason.
**Option B:** Not provided, possibly incorrect about the enzyme's characteristics.
**Option C:** Not provided, maybe mistaken about the application or property.
**Option D:** Not provided, could be wrong regarding the comparison with E. coli.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that **Taq polymerase** from **Thermus aquaticus** revolutionized PCR by enabling the use of high temperatures for DNA denaturation, significantly improving the specificity and yield of the reaction. This understanding is crucial for molecular biology applications.
**Correct Answer:** D. Taq polymerase has a higher temperature optimum.