The similarity of DNA and RNA. Comparative characteristics of DNA and RNA: table

Every living organism in our world is not like others. Not only are people different from each other. Animals and plants of the same species also have differences. The reason for this is not only different living conditions and life experience. The individuality of each organism is laid in it with the help of genetic material.

Important and interesting questions about nucleic acids

Even before the birth of each organism has its own set of genes, which determines absolutely all the features of the structure. It is not only the color of the coat or the shape of the leaves, for example. In the genes are laid and more important characteristics. After all, a cat can not have a hamster, and a baobab will not grow from wheat seeds.

And for all this huge amount of information, nucleic acids - RNA and DNA molecules - respond. Their importance is very difficult to overestimate. After all, they not only retain information throughout their lives, they help to realize it with the help of proteins, but also transmit it to the next generation. How does it work out, how complex are the DNA and RNA molecules ? What are they like and what are their differences? In all this, we will deal with the following chapters of the article.

All the information we will disassemble in parts, starting with the very basics. First we learn what nucleic acids are, how they were discovered, then we'll talk about their structure and functions. At the end of the article we are waiting for a comparative table of RNA and DNA, to which you can apply at any time.

What are nucleic acids

Nucleic acids are organic compounds having a high molecular weight, are polymers. In 1869 they were first described by Friedrich Mischer, a biochemist from Switzerland. He isolated a substance, which includes phosphorus and nitrogen, from the cells of pus. Assuming that it is located only in the nuclei, the scientist called it a nuclein. But what remained after the separation of proteins, was called nucleic acid.

Its monomers are nucleotides. Their number in an acid molecule is individual for each species. Nucleotides are molecules consisting of three parts:

• Monosaccharide (pentose), there may be two types - ribose and deoxyribose;
• A nitrogenous base (one of four);
• Phosphoric acid residue.

Next, we will consider the differences and similarities between DNA and RNA, the table at the very end of the article will summarize.

Peculiarities of the structure: pentoses

The very first similarity between DNA and RNA is that they contain monosaccharides. But for each acid they are their own. It is depending on what is in the molecule of pentose, the nucleic acids are divided into DNA and RNA. The DNA composition includes deoxyribose, and RNA - ribose. Both pentoses are found in acids only in β-form.

In deoxyribose, the second carbon atom (designated as 2 ') lacks oxygen. Scientists suggest that his absence:

• Shortens the bond between C ₂ and C ₃ ;
• Makes the DNA molecule more durable;
• Creates conditions for the compact laying of DNA in the nucleus.

Comparison of structures: nitrogen bases

Comparative characteristics of DNA and RNA are not easy. But the differences are already visible from the very beginning. Nitrogen bases are the most important "bricks" in our molecules. They carry genetic information. More precisely, not the bases themselves, but their order in the chain. They are purine and pyrimidine.

The composition of DNA and RNA differs already at the level of monomers: in deoxyribonucleic acid we can find adenine, guanine, cytosine and thymine. But RNA instead of thymine contains uracil.

These five bases are major (major), they make up most of the nucleic acids. But apart from them, there are others. This happens very rarely, such minor reasons are called. Both are found in both acids - this is another similarity between DNA and RNA.

The sequence of these nitrogenous bases (and, correspondingly, of the nucleotides) in the DNA chain determines which proteins the cell can synthesize. What molecules will be created at the moment, depends on the needs of the body.

Let us pass to the levels of organization of nucleic acids. In order for the comparative characteristics of DNA and RNA to be maximally complete and objective, we consider the structure of each. DNA has four of them, and the number of levels of organization in RNA depends on its kind.

The discovery of the structure of DNA, the principles of structure

All organisms are divided into prokaryotes and eukaryotes. This classification is based on the design of the kernel. These and other DNA is contained in the cell as chromosomes. These are special structures in which the molecules of deoxyribonucleic acid are bound to proteins. DNA has four levels of organization.

The primary structure is represented by a chain of nucleotides, the sequence of which is strictly observed for each individual organism and which are linked by phosphodiester bonds. Great successes in studying the chain structure of DNA were reached by Chargaff and his collaborators. They determined that the ratios of nitrogenous bases are subject to certain laws.

They were called the rules of Chargaff. The first of them says that the sum of purine bases should be equal to the sum of pyrimidine bases. This will become clear after acquaintance with the secondary structure of DNA. The second rule follows from its features: the molar ratios A / T and T / C are equal to one. The same rule is also true for the second nucleic acid - here is another similarity between DNA and RNA. Only the second instead of thymine everywhere is uracil.

Also, many scientists began to classify DNA of different species for more grounds. If the sum of "A + T" is greater than "Г + Ц", such DNA is called АТ-type. If on the contrary, then we are dealing with GC-type DNA.

The model of the secondary structure was proposed in 1953 by the scientists Watson and Crick, it is still universally recognized to this day. The model is a double helix, which consists of two antiparallel circuits. The main characteristics of the secondary structure are:

• The composition of each DNA chain is strictly specific for the species;
• The bond between the chains is hydrogen, is formed by the principle of complementarity of nitrogenous bases;
• Polynucleotide chains entwine each other forming a right-spiraled spiral called "helix";
• Residues of phosphoric acid are located outside the spiral, nitrogenous bases - inside.

Further, denser, more difficult

Tertiary structure of DNA is a super-spiral structure. That is, not only that in a molecule two chains are twisted with each other, for greater compactness of DNA it is wound up on special proteins - histones. They are divided into five classes, depending on the content of lysine and arginine in them.

The latest level of DNA is the chromosome. To understand how tightly the carrier of genetic information is laid in it, imagine the following: if the Eiffel Tower went through all stages of compactification, like DNA, it could be placed in a matchbox.

Chromosomes are single (consist of one chromatid) and double (consist of two chromatids). They provide reliable storage of genetic information, and if necessary can turn around and open access to the desired site.

Types of RNA, structural features

In addition to the fact that any RNA differs from DNA by its primary structure (absence of thymine, the presence of uracil), the following levels of organization also differ:

1. Transport RNA (tRNA) is a single-stranded molecule. In order to fulfill its function of transporting amino acids to the site of protein synthesis, it has a very unusual secondary structure. It is called cloverleaf. Each of its loops fulfills its function, but the most important are the acceptor stem (an amino acid clings to it) and anticodon (which must coincide with the codon on the matrix RNA). The tertiary structure of tRNA has been little studied, because it is very difficult to isolate such a molecule without disturbing the high level of organization. But some information is available from scientists. For example, in yeast the transport RNA has the form of the letter L.
2. Matrix RNA (also called information) performs the function of transferring information from DNA to the site of protein synthesis. She tells what kind of protein will turn out as a result, ribosomes move through it during the synthesis. Its primary structure is a single-stranded molecule. The secondary structure is very complex, necessary for the correct determination of the beginning of protein synthesis. MRNA is formed in the form of hairpins, at the ends of which are located the beginning and end of the processing of protein.
3. Ribosomal RNA is contained in ribosomes. These organelles consist of two subparticles, each with its own rRNA. This nucleic acid determines the location of all ribosomal proteins and functional centers of this organelle. The primary structure of rRNA is represented by a sequence of nucleotides, as in the previous versions of the acid. It is known that the final stage in the laying of rRNA is the pairing of the end sections of one chain. The formation of such petioles makes an additional contribution to the compactification of the entire structure.

Functions of DNA

Deoxyribonucleic acid serves as a storehouse of genetic information. It is in the sequence of its nucleotides that all the proteins in our body are "hidden". In DNA, they are not only stored, but also well protected. And even if an error occurs while copying, it will be fixed. Thus, all genetic material will be preserved and will reach the offspring.

In order to transmit information to descendants, DNA has the ability to double. This process is called replication. A comparison table of RNA and DNA will show us that another nucleic acid does not know how to do this. But it has many other functions.

RNA functions

Each type of RNA performs its functions:

1. Transport ribonucleic acid carries amino acids to the ribosomes, where proteins are made from them. TRNA not only brings construction material, it also participates in the recognition of the codon. And on her work depends on how correctly the protein will be built.
2. Information RNA reads information from DNA and transfers it to the site of protein synthesis. There, it attaches to the ribosome and dictates the order of the amino acids in the protein.
3. Ribosomal RNA ensures the integrity of the structure of the organelle, regulates the work of all functional centers.

Here is another similarity between DNA and RNA: they both care about the genetic information that the cell carries.

Comparison of DNA and RNA

To systematize all the above information, write it all into a table.

Thus, we briefly described how there are similarities between DNA and RNA. The table will be an indispensable assistant in the exam or a simple reminder.

In addition to what we have already learned, several facts have appeared in the table. For example, the ability of DNA to double is necessary for dividing cells, so that both cells receive the correct genetic material in full. While there is no sense in doubling for RNA. If the cell requires another molecule, it synthesizes it by the DNA matrix.

The characteristics of DNA and RNA turned out to be brief, but we covered all the features of the structure and functions. Very interesting is the process of translation - protein synthesis. After getting acquainted with it, it becomes clear how much RNA plays a role in the life of the cell. And the process of doubling DNA is very exciting. What exactly is the tearing of the double helix and the reading of each nucleotide!

Learn new every day. Especially if this new occurs in every cell of your body.