Packaging of DNA helix

Options

A. Involves polyamines in eukaryotes
B. Occurs with the help of NHC proteins only
C. Requires acidic proteins that help in coiling of DNA in prokaryotes
D. Is more complex in eukaryotes than prokaryotes

Answer

### Step-by-Step Solution for the Question: Packaging of DNA Helix

1. **Understanding DNA Length in Eukaryotes**:
- Eukaryotic cells contain a significant amount of DNA. For example, a haploid human genome has approximately 3.3 x 10^9 base pairs.
- Each base pair is about 0.34 nm in length. To find the total length of DNA in a single cell, we multiply the number of base pairs by the length of each base pair:
\[ \text{Total Length} = 3.3 \times 10^9 \text{ base pairs} \times 0.34 \text{ nm/base pair} = 1.122 \times 10^9 \text{ nm} = 1.122 \text{ m} \]
- This means that the DNA from a single cell can stretch to about 2.2 meters when fully extended.

2. **Need for DNA Packaging**:
- Given the large amount of DNA in eukaryotic cells, it must be compactly packaged to fit within the nucleus, which is much smaller than the total length of the DNA.

3. **Role of Histone Proteins**:
- The primary proteins involved in the packaging of DNA in eukaryotes are histone proteins. These proteins are rich in basic amino acids like lysine and arginine.
- DNA wraps around a core of histone proteins to form a structure known as a nucleosome.

4. **Formation of Nucleosomes**:
- Each nucleosome consists of an octamer of histone proteins (8 histones) around which approximately 166 base pairs of DNA are wrapped.
- This structure allows for the initial level of DNA compaction.

5. **Higher-Order Structures**:
- Nucleosomes further coil and fold to form more complex structures:
- Nucleosomes coil to form a solenoid structure.
- These solenoids further organize into chromatin fibers.
- Chromatin fibers condense to form chromatids, which ultimately form chromosomes.

6. **Comparison with Prokaryotic DNA Packaging**:
- In contrast, prokaryotic DNA is not associated with histone proteins; hence, it is often referred to as "naked DNA."
- Prokaryotic DNA is packaged with the help of non-histone basic proteins, such as polyamines.

7. **Conclusion**:
- The packaging of DNA in eukaryotes is more complex than in prokaryotes due to the involvement of histone proteins and the formation of higher-order structures.

### Final Answer:
The packaging of DNA helix is more complex in eukaryotes than in prokaryotes.

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