Question

Which of the following bases is not found in DNA?
a) Adenine
b) Guanine
c) Cytosine
d) Uracil

Answer 1

Hint: DNA and RNA are made up of sugar, a nitrogenous base and a phosphate group. These bases are also known as nucleobases. They form nucleosides and nucleotides. These are the building blocks of nucleic acid.

Complete answer:
There are majorly Five nucleobases —adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U). The bases A, G, C, and T are found in DNA while A, G, C, and U in RNA. Thymine and uracil are different because of the presence or absence of a methyl group on their fifth carbon of the heterocyclic six-membered rings.
Adenine (A) and guanine (G) have a fused-ring and are called purine bases and there is a simple-ring structure of cytosine, uracil, and thymine which are called the pyrimidine bases. A dsDNA comprises purine and pyrimidine where A is paired with a T and a C paired with a G. They connect the two strands of the helix.
The A–T and C–G pairings are done by double or triple hydrogen bonds (double for C-G and triple for A-T bonds) between the amine and carbonyl groups on the bases.

So, the correct answer is “Option d”.

Note:
Presence of thymine in place of uracil gives extra stability to DNA. DNA is more stable than RNA and hence is used in storing genetic information while RNA being less stable is used in transferring the genetic information.