Which is correct sequence according to increasing molecular weight ?

Options

A. tRNA- DNA- rRNA
B. tRNA - rRNA - DNA
C. rRNA- DNA- tRNA
D. DNA- tRNA - rRNA

Answer

To determine the correct sequence of biomolecules according to increasing molecular weight, we need to analyze the molecular weights of each type of RNA and DNA. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the Types of Biomolecules
- We are comparing three types of nucleic acids: tRNA (transfer RNA), rRNA (ribosomal RNA), and DNA (deoxyribonucleic acid).

### Step 2: Determine the Molecular Weight of tRNA
- tRNA is relatively small, consisting of approximately 75 to 95 nucleotides.
- Each nucleotide has a molecular weight of about 330 daltons (g/mol), so the molecular weight of tRNA can be estimated to be around:
\[ \text{Molecular weight of tRNA} \approx 75 \times 330 \text{ to } 95 \times 330 \approx 24,750 \text{ to } 31,350 \text{ daltons} \]

### Step 3: Determine the Molecular Weight of rRNA
- rRNA is larger than tRNA, with a size ranging from approximately 120 to 5,000 nucleotides, depending on the type of rRNA.
- For example, a common rRNA molecule can have a molecular weight of around 500 to 5,000 nucleotides, leading to an estimated molecular weight of:
\[ \text{Molecular weight of rRNA} \approx 500 \times 330 \text{ to } 5,000 \times 330 \approx 165,000 \text{ to } 1,650,000 \text{ daltons} \]

### Step 4: Determine the Molecular Weight of DNA
- DNA is the largest of the three, consisting of millions of nucleotides. For example, a typical human gene can have around 1,000 to 2,000 nucleotides or more.
- The molecular weight of DNA can be estimated to be significantly higher than that of both tRNA and rRNA, often in the range of:
\[ \text{Molecular weight of DNA} \approx 1,000 \times 330 \text{ to } \text{millions of daltons} \]

### Step 5: Arrange the Biomolecules by Increasing Molecular Weight
- Based on the above estimations, we can arrange the biomolecules in order of increasing molecular weight:
1. tRNA (smallest)
2. rRNA (medium)
3. DNA (largest)

### Conclusion
Thus, the correct sequence according to increasing molecular weight is:
**tRNA < rRNA < DNA**

The correct answer is **Option D: tRNA, rRNA, DNA**.

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