Choose the correct steps in the organisation of eukaryotic chromosome

Options

A. Nucleosome `to` Solenoid `to` Supersolenoid .
B. Sotenoid `to` Nucleosome `to` Chromatid
C. DNA `to` Solenoid `to` Nucleosome
D. Chormation `to` Solenoid `to` Nucleosome

Answer

To answer the question about the correct steps in the organization of eukaryotic chromosomes, we can break down the process into several key stages. Here’s a step-by-step explanation:

### Step 1: Formation of Nucleosomes
- **Explanation**: The first step in the organization of eukaryotic chromosomes is the wrapping of DNA around histone proteins to form nucleosomes. Each nucleosome consists of a segment of DNA wound around a core of eight histone proteins (two each of H2A, H2B, H3, and H4).
- **Hint**: Remember that nucleosomes are often described as "beads on a string" due to their appearance when DNA is wrapped around histones.

### Step 2: Formation of the Solenoid Structure
- **Explanation**: Nucleosomes are further coiled into a more compact structure known as the solenoid. This structure typically has a diameter of about 30 nanometers and is formed by the coiling of nucleosomes in a helical manner.
- **Hint**: Think of the solenoid as a way to increase the compactness of the DNA structure beyond the nucleosome level.

### Step 3: Formation of Chromatin Fiber
- **Explanation**: The solenoid structure can further fold and coil to form a chromatin fiber, which is approximately 80 nanometers in diameter. This fiber represents a higher level of DNA packing.
- **Hint**: Chromatin fibers are essential for organizing DNA within the nucleus and play a role in gene regulation.

### Step 4: Formation of Chromatid
- **Explanation**: During cell division, the chromatin fibers condense further to form chromatids. Each chromatid is a single, tightly coiled DNA molecule and is about 700 nanometers in diameter.
- **Hint**: Remember that chromatids are the structures that are separated during cell division, specifically during mitosis and meiosis.

### Step 5: Formation of Chromosomes
- **Explanation**: Finally, during cell division, two sister chromatids are joined at a region called the centromere to form a chromosome. The fully condensed chromosome is about 1400 nanometers in diameter.
- **Hint**: Chromosomes are the most condensed form of DNA and are visible under a light microscope during cell division.

### Summary of Correct Steps
1. Nucleosome formation
2. Solenoid structure formation
3. Chromatin fiber formation
4. Chromatid formation
5. Chromosome formation

### Conclusion
The correct sequence of steps in the organization of eukaryotic chromosomes is: Nucleosome → Solenoid → Chromatin Fiber → Chromatid → Chromosome.