Principal constituents of chromosomes are
(a) DNA+ Protein
(b) DNA
(c) RNA
(d) tRNA

Options

A. DNA+ Protein
B. DNA
C. RNA
D. tRNA

Answer

To determine the principal constituents of chromosomes, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Chromosomes**:
- Chromosomes are structures within cells that contain genetic material. They are made up of DNA and proteins.

2. **Identifying the Genetic Material**:
- The primary genetic material in chromosomes is DNA (deoxyribonucleic acid). This DNA carries the genetic instructions necessary for the growth, development, and reproduction of organisms.

3. **Role of Proteins**:
- In addition to DNA, chromosomes also contain proteins. The main type of protein associated with DNA in chromosomes is called histone proteins. These proteins help in the packaging and organization of DNA, allowing it to fit within the nucleus of the cell.

4. **Conclusion**:
- The principal constituents of chromosomes are therefore a combination of DNA and proteins (specifically histones).

5. **Selecting the Correct Option**:
- Given the options:
- (a) DNA + Protein
- (b) DNA
- (c) RNA
- (d) tRNA
- The correct answer is (a) DNA + Protein, as both components are essential for the structure of chromosomes.

### Final Answer:
The principal constituents of chromosomes are (a) DNA + Protein.

---