Final answer:
RNA is indeed usually single-stranded, which provides flexibility for its various roles in the cell, unlike the typically double-stranded structure of DNA for stable genetic storage. RNA's single-stranded form can also fold into complex structures for its functions in protein synthesis and regulation.
Step-by-step explanation:
The correct answer to the given question is a. true. Unlike DNA, RNA is usually single-stranded. This structural distinction is vital for their respective functions in the cell. DNA is typically double-stranded, which lends it the stability needed for long-term storage of genetic information. On the other hand, RNA's single-stranded nature allows it more flexibility to carry out various functions within the cell, such as protein synthesis through processes involving mRNA, tRNA, and rRNA.
Furthermore, even though RNA is single-stranded, it can fold upon itself, forming intricate three-dimensional structures stabilized by intramolecular base pairing. This base pairing can happen because of the presence of complementary base sequences within the single RNA strand. These structures are crucial for RNA's function in protein synthesis, where mRNA carries genetic instructions from DNA to the ribosomes, tRNA transfers specific amino acids to the developing polypeptide chain, and rRNA is a component of the ribosome itself. Other types of RNA like miRNA are involved in the regulation of gene expression.