Question

RNA forms loop structure because (1) It always contain uracyl instead of thymine (2) of presence of nearby complementary bases (3) all RNAs have to from loop structure to function (4) they are always single stranded

Short answer

Option 2: Presence of nearby complementary bases.

Step-by-step solution

- Understand the Question

Identify why RNA forms loop structures from the given choices. Look for the specific reason related to RNA structure.

- Evaluate Option 1

Option (1) says RNA forms loop structures because it always contains uracil instead of thymine. This is not the reason for loop formation but rather a distinguishing feature of RNA.

- Evaluate Option 2

Option (2) suggests RNA forms loops due to the presence of nearby complementary bases. This is correct as RNA strands fold back on themselves and form hydrogen bonds between complementary bases, creating loops.

- Evaluate Option 3

Option (3) states all RNAs have to form loop structures to function. This is not necessarily true; not all RNAs form loops as part of their function.

- Evaluate Option 4

Option (4) says RNA forms loops because they are always single-stranded. While RNA is typically single-stranded, loop formation specifically results from base pairing within the strand.

- Conclusion

Based on the evaluations, the reason RNA forms loop structures is due to the presence of nearby complementary bases (Option 2).

Key concepts

RNA structure

RNA, or ribonucleic acid, is a crucial molecule in living organisms. It plays a significant role in translating genetic information from DNA into proteins, which are essential for various cellular functions.
Unlike DNA, which is double-stranded, RNA is usually found as a single strand. This single strand can fold into complex three-dimensional shapes, which are vital for its function.
RNA is made up of four nucleotides: adenine (A), cytosine (C), guanine (G), and uracil (U). Notice that uracil replaces thymine, which is found in DNA.
These nucleotides are linked together by a sugar-phosphate backbone, similar to the structure of DNA, but with ribose sugar instead of deoxyribose. The unique structure of RNA allows it to perform multiple roles, from acting as a messenger carrying genetic information (mRNA) to helping in protein synthesis (tRNA and rRNA). Understanding RNA structure is key to comprehending how it functions in various biological processes.

complementary bases

Complementary bases in RNA are the key to its ability to fold into loop structures. Complementary bases are pairs of nucleotides that can form hydrogen bonds with each other. In RNA, adenine (A) pairs with uracil (U), and cytosine (C) pairs with guanine (G).
When an RNA strand folds back on itself, these complementary bases can find each other and form hydrogen bonds. This pairing is essential for the formation of stem-loop structures, where a sequence of bases pairs with a complementary sequence further down the strand, causing the intervening loop to bulge out.
These loop structures are not just random; they are critical for the RNA's function. For instance, tRNA molecules have a characteristic cloverleaf structure caused by these intramolecular base pairings. This structure is essential for tRNA to carry amino acids to the ribosome during protein synthesis.

single-stranded RNA

RNA is typically single-stranded, which differentiates it from the double-stranded DNA. This single-stranded nature grants RNA more flexibility in its structure.
The single-stranded RNA can fold into various shapes and structures, essential for its role in the cell. For example, in mRNA, the single strand allows it to be easily read by the ribosome for protein synthesis.
Because RNA is single-stranded, it can form intramolecular base pairs, leading to the formation of complex secondary structures like hairpins and loops.
These structures are vital for the stability and function of the RNA molecule. They can create binding sites for proteins or other RNAs and act as regulatory elements. The ability of RNA to form such structures is pivotal in many cellular processes, including gene regulation and the catalytic activity of ribozymes.