The primary structure of a nucleic acid contains the base sequence $GATGC...$. Which of the following chains is complementary to this sequence?

$A$ nucleotide consists of

Which base is present in $RNA$ but not in $DNA$?

According to Chargaff's rule,in a living system:

$DNA$ contains a base that is not present in $RNA$. Identify it.

The average energy of each hydrogen bond in $A-T$ pair is $x \, kcal \, mol^{-1}$ and that in $G-C$ pair is $y \, kcal \, mol^{-1}$. Assuming that no other interaction exists between the nucleotides,the approximate energy required in $kcal \, mol^{-1}$ to split the following double stranded $DNA$ into two single strands is:
$A$-$T$-$A$-$T$-$G$-$C$-$A$-$G$
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$T$-$A$-$T$-$A$-$C$-$G$-$T$-$C$