DNA restriction fragments are separated by
**Core Concept**
The underlying principle being tested is the method used to separate DNA fragments based on size. This is a fundamental concept in molecular biology, specifically in **genetic engineering** and **molecular genetics**. The process involves the use of **electrophoresis**.
**Why the Correct Answer is Right**
The correct answer is related to the technique that uses an electric field to separate DNA fragments. This technique is called **gel electrophoresis**, where the fragments are separated based on their size as they migrate through a **gel matrix**, typically made of **agarose** or **polyacrylamide**. The smaller fragments migrate faster than the larger ones, allowing for their separation.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not relate to the standard method of separating DNA fragments.
**Option B:** This is also incorrect as it is not the primary method used for separating DNA restriction fragments.
**Option C:** Similarly, this option does not accurately describe the common technique used for this purpose.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that **gel electrophoresis** is a crucial tool in molecular biology for separating and analyzing DNA fragments, including those generated by **restriction enzymes**. This technique has numerous applications in **genetic diagnosis** and **research**.
**Correct Answer:** D. Gel electrophoresis