Question

Out of the following statements, which one is true?

• A. DNA is single stranded, RNA is double stranded.
• B. There is only one type of RNA, whereas there are many types of DNA.
• C. DNA synthesizes RNA, but RNA generally cannot synthesize DNA.
• D. DNA bases are adenine, guanine, cytosine, uracil and RNA has adenine, guanine, cytosine, thymine.

Answer 1

The correct option is C DNA synthesizes RNA, but RNA generally cannot synthesize DNA.

DNA molecule is made up of two helical DNA chains that are wound around the same axis. Each chain is a polymer of deoxyribonucleotides while RNA is normally a single-stranded polymer of ribonucleotides.
There are three major types of RNA namely mRNA, tRNA and rRNA; DNA can exhibit three main forms that are termed as B-DNA, A-DNA and Z-DNA. Deoxyribonucleotide sequence of DNA template is transcribed into ribonucleotide sequence of RNA but RNA does not serve as the template for DNA synthesis. Reverse transcription is the only exception to this. DNA and RNA both have four bases, two purines and two pyrimidines, in the nucleotide chains. There are two purines namely adenine and guanine and three pyrimidines namely cytosine, thymine and uracil. The purines adenine and guanine and the pyrimidine cytosine are common to both DNA and RNA. DNA has the pyrimidine thymine; RNA has the pyrimidine uracil. Thus, the correct answer is option C.