Chromosomes are visualized through light microscope with resolution of:
**Core Concept**
Chromosomes are complex structures composed of DNA and proteins, and their visualization under a light microscope is limited by the resolution of the microscope. The resolution of a light microscope is determined by the wavelength of the light used and the numerical aperture of the objective lens.
**Why the Correct Answer is Right**
The correct answer is based on the concept of resolution in microscopy. The resolution of a light microscope is approximately 200-250 nanometers (nm), which is the minimum distance between two points that can be distinguished as separate. This is due to the diffraction limit of light, which is the limit beyond which the light cannot be focused to a smaller area. The resolution of a light microscope is not sufficient to visualize individual chromosomes, which are typically 1-10 micrometers (μm) in size. However, by using specific staining techniques, such as Giemsa staining, and preparing the chromosomes through a process called squashing, it is possible to visualize chromosomes under a light microscope.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the resolution of an electron microscope is typically in the range of 0.1-10 nm, which is much higher than that of a light microscope.
* **Option B:** This option is incorrect because the resolution of a scanning electron microscope (SEM) is also much higher than that of a light microscope, typically in the range of 1-100 nm.
* **Option C:** This option is incorrect because the resolution of a transmission electron microscope (TEM) is also much higher than that of a light microscope, typically in the range of 0.1-10 nm.
**Clinical Pearl / High-Yield Fact**
The resolution of a light microscope is a limiting factor in the visualization of chromosomes, and special staining techniques and preparation methods are required to visualize chromosomes under a light microscope.
**Correct Answer: D. 200-250 nm**