The tangent plane at the point x=a, y=b is the plane that contains all the tangent vectors (at the point) of curves on the surface that pass through the point (a,b,f(a,b)). Another way to define it is to say that this is the plane through the point (a,b,f(a,b)) which is perpendicular to the NORMAL to the surface at that point. The NORMAL to the surface at a point is just defined as the direction perpendicular to all tangent vectors to the surface at that point. Therefore all we need to do to find the equation of the tangent plane is to find a normal to the surface at that point.
Apart from adenine (A), cytosine (C), guanine (G), thymine (T) and uracil (U), DNA and RNA also contain bases that have been modified after the nucleic acid chain has been formed. In DNA, the most common modified base is 5-methylcytosine (m 5 C). In RNA, there are many modified bases, including those contained in the nucleosides pseudouridine (Ï), dihydrouridine (D), inosine (I), and 7-methylguanosine (m 7 G).
Nucleic acids are made of monomers known as nucleotides. There are 3 parts to nucleotides: one of 4 nitrogenous bases, a sugar, and a phosphate group. RNA as well as DNA are both nucleotides. The four bases in DNA are: Adenine, Guanine, Cytosine and Thymine (present in DNA only). Plus a slightly different base: Uracil (present in RNA only).