Differences between DNA and RNA

All organisms have nucleic acids. They may not be so well known by this name, but if I say "DNA" things may change.

The genetic code is considered a universal language because it is used by all types of cells to save the information of its functions and structures, which is why even viruses use it to subsist.

In the article I will focus on clarify the differences between DNA and RNA to understand them better.

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What are DNA and RNA?

There are two types of nucleic acids: deoxyribonucleic acid, abbreviated as DNA or DNA in its English nomenclature, and ribonucleic acid (RNA or RNA). These elements are used to make copies of cells, which will build the tissues and organs of living beings in some cases, and unicellular life forms in others.

DNA and RNA are two very different polymers, both in structure and in function; however, they are both related and essential for the correct functioning of cells and bacteria. After all, although its "raw material" is different, its function is similar.

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Nucleotides

Nucleic acids are made up of chains of chemical units called "nucleotides". To put it in some way, they are like the bricks that make up the genotype of the different forms of life. I will not go into much detail about the chemical composition of these molecules, although therein lie several of the differences between DNA and RNA.

The centerpiece of this structure is a pentose (a 5-carbon molecule), which in the case of RNA is a ribose, while in DNA it is a deoxyribose. Both give names to the respective nucleic acids. Deoxyribose gives more chemical stability than ribose, which makes the structure of DNA more secure.

Nucleotides are the building block for nucleic acids, but they also play an important role as a free molecule in energy transfer in metabolic processes cells (for example in ATP).

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Structures and types

There are several types of nucleotides and not all of them are found in both nucleic acids: adenosine, guanine, cytosine, thymine, and uracil. The first three are shared in the two nucleic acids. Thymine is only in DNA, while uracil is its RNA counterpart.

The configuration that nucleic acids take is different depending on the form of life that is being talked about. In the case of eukaryotic animal cells such as humans Differences between DNA and RNA are observed in their structure, in addition to the different presence of the nucleotides thymine and uracil mentioned above.

The differences between RNA and DNA

Below you can see the basic differences between these two types of nucleic acid.

1. DNA

Deoxyribonucleic acid is structured by two chains, which is why we say that it is double-stranded. These chains draw the famous double helix linear, because they intertwine with each other as if they were a braid. At the same time, the DNA chains are coiled in the chromosomes, entities that remain grouped inside the cells.

The union of the two DNA strands occurs through links between the opposite nucleotides. This is not done randomly, but each nucleotide has an affinity for one type and not another: adenosine always binds to a thymine, while guanine binds to cytosine.

In human cells there is another type of DNA apart from nuclear: mitochondrial DNA, genetic material which is located inside the mitochondria, an organelle in charge of cellular respiration.

Mitochondrial DNA is double-stranded but its shape is circular rather than linear. This type of structure is the one typically observed in bacteria (prokaryotic cells), for what it is thought that the origin of this organelle could be a bacterium that joined the cells eukaryotes.

2. RNA

Ribonucleic acid in human cells is found in a linear fashion but it is single-stranded, that is, it is configured by forming only one chain. Also, comparing their size, their chains are shorter than DNA chains.

However, there is a wide variety of RNA types, three of which are the most prominent, since they share the important function of protein synthesis:

• Messenger RNA (mRNA): acts as an intermediary between DNA and the synthesis of protein.
• Transfer RNA (tRNA): transports amino acids (units that make up proteins) in protein synthesis. There are as many types of tRNA as there are amino acids used in proteins, specifically 20.
• Ribosomal RNA (rRNA): they are part, together with proteins, of the structural complex called ribosome, which is responsible for carrying out protein synthesis.

Duplication, transcription and translation

The names of this section are three very different processes linked to nucleic acids, but easy to understand.

Duplication only involves DNA. It occurs during cell division, when the genetic content is replicated. As the name suggests, it is a duplication of genetic material to form two cells with the same content. It is as if nature made copies of the material that will later be used as a blueprint that indicates how an element has to be built.

Transcription, on the other hand, affects both nucleic acids. In general, DNA needs a mediator to "extract" information from genes and synthesize proteins; for this it makes use of RNA. Transcription is the process of passing the genetic code from DNA to RNA, with the structural changes that it entails.

Finally, translation only acts on RNA. The gene already contains the instructions on how to structure a specific protein and has been transcribed into RNA; now all we need is move from nucleic acid to protein.

The genetic code contains different combinations of nucleotides that have a meaning for protein synthesis. For example, the combination of the nucleotides adenine, uracil, and guanine in RNA always indicates that the amino acid methionine will be placed. Translation is the passage from nucleotides to amino acids, that is, what is translated is the genetic code.

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Bibliographic references:

• Alquist, P. (2002). RNA-Dependent RNA Polymerases, Viruses, and RNA Silencing. Science 296 (5571): 1270-1273.
• Dahm, R. (2005). Friedrich Miescher and the discovery of DNA. Developmental Biology 278 (2): 274-288.
• Dame, R.T. (2005). The role of nucleoid-associated proteins in the organization and compaction of bacterial chromatin. Mol. Microbiol. 56 (4): 858-70.
• Hüttenhofer, A., Schattner, P., Polacek, N. (2005). Non-coding RNAs: hope or hype?. Trends Genet 21 (5): 289-297.
• Mandelkern, M., Elias, J., Eden, D., Crothers, D. (1981). The dimensions of DNA in solution. J Mol Biol. 152(1): 153 - 161.
• Tuteja, N., Tuteja, R. (2004). Unraveling DNA helicases. Motif, structure, mechanism and function. Eur J Biochem 271 (10): 1849-1863.