What is the full form of $EtBr$?

If the nucleotide sequence of a probe is $3'-ATCAGC-5'$,which of the following strands will it hybridize with?

Which of the following is incorrect for $DNA$ structure?

In sea urchin $DNA$,which is double stranded,$17\%$ of the bases were shown to be cytosine. The percentages of the other three bases expected to be present in this $DNA$ are

In $B-DNA$,the rise per base pair would be

$A$: In a $DNA$ molecule,the proportion of purine and pyrimidine bases is equal.
$R$: In $DNA$,two purines or two pyrimidines do not pair opposite each other.