Chargaff's base complimentarity rules are applicable to
(a) dsDNA
(b) mRNA
(c) ssDNA
(d) rRNA

Options

A. dsDNA
B. mRNA
C. ssDNA
D. rRNA

Answer

To solve the question regarding Chargaff's base complementarity rules, we need to analyze each option provided:

1. **Understanding Chargaff's Rules**: Chargaff's rules state that in double-stranded DNA, the amount of adenine (A) is equal to thymine (T), and the amount of guanine (G) is equal to cytosine (C). This is due to the specific pairing of bases: A pairs with T and G pairs with C.

2. **Evaluating the Options**:
- **(a) dsDNA (double-stranded DNA)**: This is the primary context in which Chargaff's rules apply. The complementary base pairing occurs here, which is the basis of the rules.
- **(b) mRNA (messenger RNA)**: mRNA is single-stranded and does not exhibit base complementarity in the same way as double-stranded DNA. It is synthesized based on the DNA template but does not follow Chargaff's rules.
- **(c) ssDNA (single-stranded DNA)**: Similar to mRNA, single-stranded DNA does not exhibit the base pairing that Chargaff's rules describe, as there is no complementary strand.
- **(d) rRNA (ribosomal RNA)**: rRNA is also single-stranded and does not follow Chargaff's rules, as it does not have a complementary strand for base pairing.

3. **Conclusion**: Based on the analysis, the only option where Chargaff's base complementarity rules apply is **(a) dsDNA (double-stranded DNA)**.

### Final Answer:
**(a) dsDNA**