What is the unit consisting of a base,sugar,and phosphate in nucleic acids called?

The reason for the double helical structure of $DNA$ is the operation of

The number of hydrogen bonds between guanine and cytosine; and between adenine and thymine in $DNA$ is

$DNA$ fingerprinting is a technique used to identify individuals by their genetic makeup. It relies on the fact that the sequence of nucleotides in $DNA$ is unique to every individual,except for identical twins. The process involves isolating $DNA$,fragmenting it using restriction enzymes,separating the fragments via gel electrophoresis,and then using probes to visualize specific patterns ($DNA$ profiles). Uses: $1$. Forensic investigations for solving crimes. $2$. Determining paternity or maternity. $3$. Identifying genetic disorders and hereditary diseases.

Which one is found in $ATP$ ribonucleotide?

Which nitrogen atom of a purine base is bonded with the furanose sugar to form a nucleoside?