What are two important differences in the structures of DNA and RNA? The sugar of RNA is ribose, rather than DNA's deoxyribose. The base uracil substitutes for DNA's thymine. The sugar of RNA is deoxyribose, rather than DNA's ribose. The base thymine substitutes for DNA's uracil. RNA always has a single strand, while DNA always has a double strand. DNA always has a single strand, while RNA always has a double strand.
