Question
Answers

Bases common to RNA and DNA is?
A. adenine, guanine, cytosine
B. adenine, uracil, cytosine
C. adenine, guanine, thymine
D. guanine, uracil, thymine

Answer
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Hint: Nucleic acids are the organic compound that forms the genetic material of the cell such as DNA and RNA. Nucleic acid consists of nucleotides, a pentose sugar, nitrogenous base and a phosphate group. It is mainly considered as a macromolecule.

Complete Step by Step Answer:
 -As we all know that DNA or DeoxyriboNucleic Acid and RNA or ribonucleic acid are found in the chromosomes.
-DNA is more stable due to its structure and the properties than RNA.
-DNA is made up of nucleotides and its backbone contributes pentose sugar, a phosphate group and nitrogenous base.
-Now, there are four types of nitrogenous base i.e. adenine, guanine, cytosine and thymine.
-Adenine makes two hydrogen bonds with thymine and cytosine makes three hydrogen bonds with the guanine only.
-The nitrogenous base is attached to the pentose sugar.
-Now, let's study the structure of RNA that is also made up of nucleotides and its backbone contributes pentose sugar, a phosphate group and nitrogenous base.
-Now, there are four types of nitrogenous base i.e. adenine, guanine, cytosine and uracil.
-Adenine makes two hydrogen bonds with uracil and cytosine makes three hydrogen bonds with the guanine only.
-So, we can conclude that adenine, guanine and cytosine are present in both DNA and RNA.
-So, they are the common nitrogenous base in the DNA and RNA.
-Therefore, option A is the correct answer.
-In option B, uracil is mentioned but it is not present in the DNA so, it is an incorrect answer.
-In option C, thymine is mentioned but it is not present in the RNA so, it is an incorrect answer.
-In option D, uracil is mentioned but it is not present in the DNA and thymine is not found in RNA. So, it is an incorrect answer.

Hence, the correct option is A.

Note: DNA has a double-stranded structure whereas RNA is a single-stranded structure. RNA has a main role in protein synthesis and DNA has a main role in DNA replication through transcription.