LIFE SCIENCE

Detailed explanation-1: -RNA nucleotides contain the nitrogenous bases adenine, cytosine, and guanine. However, they do not contain thymine, which is instead replaced by uracil, symbolized by a “U.” RNA exists as a single-stranded molecule rather than a double-stranded helix.

Detailed explanation-2: -In molecular biology, the term double helix refers to the structure formed by double-stranded molecules of nucleic acids such as DNA.

Detailed explanation-3: -RNA contains uracil, while DNA contains thymine. All of the other statements are true. Note that DNA is usually double-stranded and RNA is usually single-stranded, but both can exist in the opposite configuration under certain conditions.

Detailed explanation-4: -RNA can fold into specific structures. RNA is largely single-stranded, but it often contains short stretches of nucleotides that can form conventional base-pairs with complementary sequences found elsewhere on the same molecule.