Correct order of molecular weight is :-

Options

A. DNA `lt` r-RNA `lt` t-RNA
B. DNA `lt` m-RNA `lt` r-RNA
C. t-RNA `lt` m-RNA `lt` DNA
D. t-RNA `lt` DNA `lt` m-RNA

Answer

To determine the correct order of molecular weight among DNA, RNA, and tRNA, we need to analyze the molecular weights of these nucleic acids.

### Step-by-Step Solution:

1. **Understanding Molecular Weight**:
- Molecular weight refers to the mass of a molecule, typically measured in Daltons (Da). In the context of nucleic acids, it is influenced by the number of nucleotides present in the molecule.

2. **Molecular Weight of DNA**:
- DNA (Deoxyribonucleic Acid) is a double-stranded molecule that contains a large number of nucleotides. It is typically the largest in molecular weight compared to RNA molecules because it contains more nucleotides and has a more complex structure.

3. **Molecular Weight of rRNA**:
- rRNA (Ribosomal RNA) is the largest and most abundant type of RNA in the cell, constituting about 70-85% of total RNA. It is synthesized by RNA polymerase I in eukaryotes and has a significant molecular weight due to its size and abundance.

4. **Molecular Weight of mRNA**:
- mRNA (Messenger RNA) is synthesized by RNA polymerase II and varies in size depending on the gene it is transcribing. However, it is generally smaller than rRNA.

5. **Molecular Weight of tRNA**:
- tRNA (Transfer RNA) is synthesized by RNA polymerase III and is the smallest among the three types of nucleic acids. It has a relatively low molecular weight compared to DNA, rRNA, and mRNA.

6. **Arranging in Order**:
- Based on the analysis, we can arrange the molecular weights from highest to lowest:
- **DNA** (highest molecular weight)
- **rRNA** (second highest)
- **mRNA** (varies, but generally lower than rRNA)
- **tRNA** (lowest molecular weight)

### Final Order of Molecular Weight:
- **DNA > rRNA > mRNA > tRNA**