Why RNA is not easy to form a double helix

RNA is generally single-stranded and can only form a double helix by folding itself back to form a local pairing. And thanks to ribose 2'With the presence of a hydroxyl group, only the A-type double helix can be formed, which is different from the B-type double helix of DNA.

The two main ingots in the DNA, composed of pentose and phosphate groups, are intertwined with each other in an antiparallel manner and in the right-hand direction to form the backbone of the double helix. The backbone is on the outer surface of the double helix due to its hydrophilic nature and the bases are located on the inside of the double helix due to its degree of hydrophobicity. This structure is a B-type double helix structure.

RNA is generally single-stranded and can only form a double helix by folding itself back to form a local pairing. Only the local area of native RNA is a double helix structure. These double-stranded structures are due to the fact that the RNA single-stranded molecules fold back by themselves so that the complementary base pairs meet, and the hydrogen bonds combine to form an antiparallel right-hand double helix structure.

And due to ribose 2'The presence of a hydroxyl group can only form a type A double helix (similar to the structure formed by DNA dehydration), which is different from the B type double helix of DNA.

DNA is a double helix structure.

RNA is single-stranded.

Hehe, I'll briefly explain to you, what you asked is the content of university textbooks. (Note: The following are all personal inductions) 1. The triple helix and quadruple helix of DNA are composed of only 3 and 4 nucleotide strands of DNA, respectively.

That is to say, DNA can be divided into single strands, double strands, triple strands, and quadruple strands according to the number of nucleotide chains. (All are made of the same 4 deoxynucleotides.)

Formation) of single-stranded DNA without bases.

Pairing; Double-stranded DNA base pairing, you know; Three-stranded DNA is 3 nucleotide strands that are base-linked to each other and look like triangles in cross-section.

of the 3 vertices; Four-stranded DNA, that is, 4 nucleotide strands connected by bases, with a cross-section of 4 vertices in a rectangle. The principle of base hydrogen bond formation of the triple and quadruple chains is far beyond the scope of your knowledge, so I won't explain it; And these two situations are rare, you can ignore them and just understand them. 2. Supercoiled DNA refers to the concentrated body formed by linear DNA after multiple winding and concentration.

As you can imagine, it's like twisting twisted many times) and as for why it's called "supercoiled", you just have to remember the term, because it involves the specific process of "winding and concentrating" DNA: it is formed by the introduction of negative supercoiling into DNA by enzymes. Supercoiled DNA is just a form of DNA that exists and is not classified.

However, we generally divide DNA into: supercoiled DNA, ring-opening DNA (ring-opening DNA refers to circular double-stranded DNA with only one strand broken in one strand), and single-stranded double-helix.

In the structure, each turn of the helix has 10 bases on a chain. There are a total of 20 bases on the double strand. 4. It is not the base that controls the rotation of DNA, and the DNA is not rotary, but the helical conformation of DNA is determined by its environment and intermolecular forces.

In general, it is a double helix. In exceptional cases, it is not spiral (zigzag). Above, I explained it on the basis that you are a high school student. If you have more knowledge or questions, please send us a follow-up.

DNA forms an A-type structure at a relative humidity of 75, and it is also a right-handed helix, but it is shorter and thicker, with 11 base pairs per turn. Its biological significance lies in the fact that it is very similar in conformation to double-stranded RNA and DNA-RNA hybrids in solution. Due to the presence of 2'-hydroxyl groups, RNA is not easy to adopt a B-type conformation, so when transcribing, DNA should adopt a A-type conformation.

DNA also has a left-handed helix, or Z-DNA. Its skeleton is serrated and found in oligomeric DNA alternating with purines and pyrimidines, and it is also an antiparallel complementary double helix, with 12 base pairs per turn and an elongated helix. As a special structural marker, Z-DNA is related to the regulation of gene expression.

RNA is available in double-stranded and single-stranded products.

There are three types of RNA:

tRNA: carrying RNA, single-stranded, primary structure, clover-shaped, with four rings, and inverted L-shaped secondary structure.

mRNA: Messenger RNA, which is a single-stranded structure. It is transcribed from DNA.

RRNA: Ribosomal RNA, a constituent of ribosomes.

In viruses, as a heritage substance, RNA has a double-stranded and single-stranded structure.

In order to make the genetic material more stable, if the single-stranded RNA is used as the genetic material, the RNA virus is more prone to genetic mutations, and in most cases, genetic mutations are harmful.

Base packing force complex refers to the force formed by the combination of base pairs stacked on the inner side of the double helix in the DNA double helix structure, and the adjacent hydrophobic bases are stacked together with each other and attracted to each other during the precession. The main force to maintain the stability of the DNA double helix structure is the base packing force, and the base packing force when the double helix structure is formed can make the structure tend to a steady state the most, because the base packing force is the largest at this time.

The DNA molecule presents a bispiral.

The reason for the spiral structure is that the double helix structure is the result of evolution. The double helix is more stable than the single strand, which can be tolerated to ensure genetic stability.

DNA is deoxyribonucleic acid, also known as deoxyribonucleotide, which is the main component of chromosomes and is also the main genetic material. The double helix structure of the DNA molecule is relatively stable. This is because on the inner side of the double helix structure of the DNA molecule, the long strands of two deoxynucleotides are firmly linked together by the base pairs formed by hydrogen bonds.

In addition, the longitudinal interaction forces between base pairs further strengthen the stability of the DNA molecule. This longitudinal interaction between the individual base pairs is called the base stacking force, which is caused by the interaction between the aromatic base electrons. Base stacking is now generally accepted as the most important factor in stabilizing DNA structure.

In addition, the ionic bond formed between the negatively charged phosphate group on the outside of the double helix and the positively charged cation can reduce the electrostatic repulsion between the double strands, so it also has a certain stabilizing effect on the structure of the DNA double helix.