AP BIOLOGY

Detailed explanation-1: -Single-stranded RNA (ssRNA) is the simplest form of genetic molecule and constitutes the genome in some viruses and presumably in primitive life-forms. However, an innate and unsolved problem regarding the ssRNA genome is formation of inactive double-stranded RNA (dsRNA) during replication.

Detailed explanation-2: -The chemical structure of RNA is very similar to that of DNA, but differs in three primary ways: Unlike double-stranded DNA, RNA is usually a single-stranded molecule (ssRNA) in many of its biological roles and consists of much shorter chains of nucleotides.

Detailed explanation-3: -Which molecule is always single-stranded? RNA is always single-stranded and is often referred to as single-stranded ribonucleic acid. This can be seen in Figure 1 below. However, DNA can be either double-stranded or a single strand of DNA (ssDNA).

Detailed explanation-4: -Nucleic acid aptamers are short, single-stranded DNA or RNA oligonucleotides, which adopt stable three-dimensional sequence-dependent structures. This intrinsic property makes them efficient bioreceptors for different molecular targets (from small ions and organic molecules to large proteins, and even cells).