What type of bond exists between $A$ (Adenine) and $T$ (Thymine)?

Who proposed that for a double-stranded $\text{DNA},$ the ratios between Adenine and Thymine and Guanine and Cytosine are constant and equal to one?

Who provided the data for $X$-ray diffraction of $DNA$?

Nucleosome is made up of

Provide definitions/explanations for the following terms: $Nucleosome$ and $Euchromatin$.

One turn of $DNA$ possesses