Chapter 23, Problem 13RQ

To determine

The four nitrogenous bases that are found in DNA and RNA.

Answer to Problem 13RQ

The nitrogenous bases that are present in DNA are adenine, guanine, thymine and cytosine whereasthe bases which are present in RNA are adenine, guanine, uracil and cytosine.

Explanation of Solution

The structure of deoxyribonucleic acid that is DNA is postulated by Watson and Crick as a double helical structure. In DNA, the sugar is a deoxyribose sugar and heterocyclic bases are adenine, guanine, thymine and cytosine. The nucleotide chain in DNA has alternate sugar and phosphate ester residues. The phosphoric acid on one side forms ester linkage with $3\text{'}-\text{OH}$ of one sugar and on other side it forms ester linkage with $5\text{'}-\text{OH}$ of the another sugar residue.

The ribonucleic acid that is RNA exists as a single stranded helix. The structure of RNA is similar to that of DNA except that the sugar in it is ribose sugar and uracil is present instead of thymine as a heterocyclic base. The DNA and RNA are involved in protein biosynthesis, which involves two important processes of transcription and translation.

Conclusion:

The nitrogenous bases that are in DNA are adenine, guanine, thymine and cytosine. However, the bases which are present in RNA are adenine, guanine, uracil and cytosine.