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

Every living organism in our world is not like the others. Not only people differ 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 birth, each organism has its own personal set of genes, which determines absolutely all the structural features. It is not only the color of the coat or the shape of the leaves, for example. More important characteristics are laid in genes. After all, a hamster cannot be born in a cat, and baobab will not grow from wheat seeds.

And for all this huge amount of information, nucleic acids - RNA and DNA molecules are responsible. Their importance is very difficult to overestimate. After all, they not only preserve information throughout life, they help to realize it with the help of proteins, but in addition, pass it on to the next generation. How do they get it, how complex are the structures of DNA and RNA molecules? How are they similar and what are their differences? In all this we will figure it out in the following chapters of the article.

We will analyze all the information in parts, starting with the very basics. First we find out what nucleic acids are, how they were discovered, then we will talk about their structure and functions. At the end of the article, we are waiting for a comparative table of RNA and DNA, which you can refer to at any time.

What are nucleic acids

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

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

• monosaccharide (pentose), can be of two types - ribose and deoxyribose;
• nitrogen base (one of four);
• phosphoric acid residue.

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

Features of a structure: pentoses

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

In deoxyribose at the second carbon atom (denoted as 2 ') there is no oxygen. Scientists suggest that its absence:

• shortens the bond between C ₂ and C ₃ ;
• makes a DNA molecule more durable;
• creates the conditions for compact folding of DNA in the nucleus.

Comparison of buildings: nitrogenous bases

Comparative characterization of DNA and RNA is not an easy task. But the differences are visible from the very beginning. Nitrogen bases are the most important building blocks in our molecules. They carry the genetic information. More precisely, not the grounds themselves, but their order in the chain. They are purine and pyrimidine.

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

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

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

Let's move on to the levels of organization of nucleic acids. In order for the comparative characteristics of DNA and RNA to be as complete and objective as possible, we will consider the structure of each. DNA has four, and the number of levels of organization in RNA depends on its type.

Discovery of DNA structure, structural principles

All organisms are divided into prokaryotes and eukaryotes. This classification is based on the core design. In those and other DNA is contained in the cell in the form of chromosomes. These are special structures in which deoxyribonucleic acid molecules 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 interconnected by phosphodiester bonds. Huge success in the study of the DNA chain structure was achieved by Charguff and his colleagues. They determined that the ratios of nitrogenous bases obey 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 becoming acquainted with the secondary structure of DNA. From its features, the second rule also follows: the molar ratios A / T and G / C are equal to unity. The same rule is true for the second nucleic acid - here is another similarity of DNA and RNA. Only the second has uracil everywhere instead of thymine.

Also, many scientists began to classify DNA of different species for a greater number of bases. If the sum of "A + T" is greater than "G + C", this DNA is called the AT type. If on the contrary, then we are dealing with the HZ type of DNA.

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

• the composition of each DNA strand is strictly species-specific;
• the bond between the chains is hydrogen, is formed by the principle of complementarity of nitrogenous bases;
• polynucleotide chains wrap around each other to form a right-handed helix called helix;
• residues of phosphoric acid are located outside the spiral, nitrogenous bases inside.

Farther, denser, harder

The tertiary structure of DNA is a supercoiled structure. That is, not only that in the molecule two chains are twisted together, for greater compactness the DNA is wound on special proteins - histones. They are divided into five classes depending on the content of lysine and arginine in them.

The most recent DNA level 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 compaction, 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 deploy and open access to the desired site.

Types of RNA, structural features

In addition to the fact that any RNA differs from DNA in its primary structure (absence of thymine, 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 a clover leaf. Each loop of it performs its function, but the most important are the acceptor stem (an amino acid clings to it) and the anticodon (which should coincide with the codon on messenger RNA). The tertiary structure of tRNA is little studied, because it is very difficult to isolate such a molecule without violating the high level of organization. But scientists have some information. For example, in yeast, transport RNA is in the form of the letter L.
2. Matrix RNA (also called informational) performs the function of transferring information from DNA to the site of protein synthesis. She reports what kind of protein will turn out in the end, ribosomes move along it in the synthesis process. Its primary structure is a single chain molecule. The secondary structure is very complex, it is necessary for the correct determination of the beginning of protein synthesis. mRNA is folded in the form of hairpins, at the ends of which there are sites of the beginning and end of protein processing.
3. Ribosomal RNA is found in ribosomes. These organelles consist of two subparticles, each of which has its own rRNA. This nucleic acid determines the location of all ribosomal proteins and the functional centers of this organelle. The primary structure of rRNA is represented by a nucleotide sequence, as in previous varieties of acid. It is known that the final stage of rRNA folding is the pairing of the terminal sections of one chain. The formation of such petioles makes an additional contribution to the compaction of the entire structure.

DNA functions

Deoxyribonucleic acid serves as a repository of genetic information. It is in the sequence of its nucleotides that all the proteins of 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 comparative table of RNA and DNA will show us that another nucleic acid does not know how to do this. But she has many other functions.

RNA Functions

Each type of RNA performs its functions:

1. Transport ribonucleic acid delivers amino acids to the ribosomes, where proteins are made from them. tRNA not only brings building material, it is also involved in the recognition of the codon. And from her work depends on how correctly the protein will be built.
2. Informational 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 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's another similarity between DNA and RNA: they both care about the genetic information that a cell carries.

Comparison of DNA and RNA

To systematize all the above information, we write all of it in a table.

Thus, we briefly talked about the similarities between DNA and RNA. The table will be an indispensable assistant in the exam or a simple memo.

In addition to what we already learned earlier, several facts appeared in the table. For example, the ability of DNA to double is necessary for cell division, so that both cells receive the correct genetic material in full. While for RNA, doubling does not make sense. If a cell needs another molecule, it synthesizes it using a DNA matrix.

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

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