Q.Some of the following statements apply to DNA only, some to RNA only and some to both. Label them accordingly.
a. The polynucleotide is double stranded. ( )
b. The polynucleotide contains uracil. ( )
c. The polynucleotide contains D-ribose ( ).
d. The polynucleotide contains Guanine ( ).

Step 1 (a). 'The polynucleotide is double stranded': section 14.4.3 states DNA forms a double helix (two strands) while RNA exists as a single-stranded structure -- so double-strandedness applies to DNA only.

Step 2 (b). 'The polynucleotide contains uracil': section 14.4.1 states uracil (U) occurs only in RNA (DNA uses thymine, T, instead) -- so this applies to RNA only.

Step 3 (c). 'The polynucleotide contains D-ribose': section 14.4.1 states the sugar in RNA nucleotides is D-ribose, while DNA nucleotides use 2-deoxy-D-ribose instead -- so plain D-ribose applies to RNA only.

Step 4 (d). 'The polynucleotide contains Guanine': guanine (G) is one of the five nitrogen bases and, per the Remember box (RNA: D-ribose, A, G, C, U; DNA: D-2-deoxyribose, A, G, C, T), it is present in BOTH DNA and RNA -- so this applies to both.

Check each statement against the DNA-vs-RNA composition facts of sections 14.4.1 and 14.4.3: double helix and thymine/deoxyribose are DNA-specific; uracil and plain ribose are RNA-specific; adenine and guanine occur in both.

• Assuming uracil occurs in both DNA and RNA (it occurs only in RNA; DNA has thymine instead).
• Assuming D-ribose is the sugar for DNA rather than RNA (DNA uses 2-deoxy-D-ribose, a different sugar).