Correct option is B
In this case, the base composition of the genome of the virus shows an imbalance in the percentage of bases. According to Chargaff's rules, in double-stranded DNA, adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C), meaning the percentage of adenine should equal thymine, and the percentage of guanine should equal cytosine. However, in the given base composition (Adenine: 25%, Cytosine: 35%, Guanine: 30%, Thymine: 10%), the amounts of adenine and thymine are not equal, and the amounts of guanine and cytosine are also not equal. This suggests the genome is single-stranded DNA (ssDNA), which does not follow the complementary base pairing rules, unlike double-stranded DNA.
Information Booster:
Single-stranded DNA (ssDNA) does not follow Chargaff's rules because it consists of only one strand, which does not require complementary base pairing.
In ssDNA, there is no pairing of adenine with thymine or guanine with cytosine, so the proportions of these bases can vary significantly.
This imbalance in the base composition is a key indicator of a single-stranded DNA genome.
ssDNA is found in certain viruses, including some bacteriophages and animal viruses, and does not exhibit the strict base-pairing rules of double-stranded DNA.
Unlike double-stranded DNA, ssDNA can exist in various conformations and is typically more prone to mutations due to the lack of complementary strand support.
The presence of thymine (instead of uracil, which would be found in RNA) confirms that this is a DNA virus, not an RNA virus.
Additional Knowledge:
Double-stranded DNA (option 1) follows Chargaff's rules where adenine pairs with thymine and guanine pairs with cytosine, which does not match the given base composition.
Double-stranded RNA (option 3) involves uracil instead of thymine, and its base composition would not resemble that of the given virus.
Single-stranded RNA (option 4) also involves uracil instead of thymine, and its base composition would differ from what is presented in this case.
