Question

The nucleobase present in RNA but not in DNA is
A.Adenine
B.Guanine
C.Cytosine
D.Uracil

Answer 1

Uracil base of pyrimidines is found only in RNA and not in DNA and the difference between DNA and RNA is an extra base of pyrimidines called uracil that binds to adenine along with other base pair instead of thymine.

Complete step by step answer:
Usually there are four bases out of which, two of them, namely, adenine and guanine, are referred as purines; and the other two, namely, thymine and cytosine, are referred to as pyrimidines. The sequence of base pairs where pyrimidines always base paired with purines, is the key to the hereditary determining qualities of DNA and its capability to form proteins and RNA.
DNA and RNA both are made of nucleotides and nucleotides are made up of Sugar (ribose in case of RNA) (Deoxyribose in case of DNA), phosphate and nitrogen base. DNA contains Adenine (A), Guanine (G), Thymine (T) and Cytosine (C).
The difference between DNA and RNA is an extra base of pyrimidines called Uracil which binds to adenine $\left( {A - U} \right)$ along with other base pair $\left( {G - C} \right)$ instead of thymine.
So, the nucleobase present in RNA but not in DNA is Uracil.
Therefore, the correct answer is option (D).

Note: In DNA thymine binds to adenine $\left( {A - T} \right)$ along with another base pair $\left( {G - C} \right)$ in sequence. DNA is the constituent of the nucleus of the cell while the nucleolus of the cell is made up of RNA that is known for the manufacturing of proteins. The mRNA transports the formed proteins to the nucleus where DNA organises the genetic (hereditary) mechanism of the individual.