Deoxyribonucleic acid (abbreviated DNA) is the molecule that carries our genetic information for the development and functioning of an organism. It consists of more than 3 billion base pairs ("lethrites") in each of the cells of our body.
What is DNA for?
DNA is essential for life and its proper functioning, as it is responsible for the transmission and regulation of genetic information and the synthesis of proteins.
It mainly stores genetic information, information that makes us who we are and makes it possible for us to be alive. It is responsible for synthesizing the functional units of our body (proteins) and regulating the expression of genes.
It also serves as the primary unit of inheritance in all living beings. In other words, every time an organism reproduces, a portion of its DNA is passed on to its offspring. This total or partial transmission of an organism's DNA helps ensure a certain level of continuity from one generation to the next, while allowing slightly changes that contribute to the diversity of life, the adaptation of species, and their evolution.
And you may wonder, how is it possible that a cell (not visible for the human eye) can storage more than 3,000 million letters that are equivalent to 2 meters in length?
This is possible thanks to the compaction in which DNA and its complex structure are found. DNA consists of different levels of condensation being de lower to higher:
DNA is composed of a linear sequence of nucleotides, which are the structural units of the DNA molecule. Each nucleotide is composed of a nitrogenous base, a phosphate group and a five-carbon sugar (deoxyribose). The nitrogenous base can be adenine (A), thymine (T), cytosine (C) or guanine (G).
DNA double helix
The DNA molecule is a double helix, in which two strands of nucleotides are wound together to form a spiral structure. The two strands of DNA are linked by hydrogen bonds between complementary nitrogenous bases. Each strand of a DNA molecule is composed of a long strand of nucleotide monomers.
The DNA molecule is organized into nucleosomes thanks to histones. Histones are essential proteins for maintaining the structure of DNA which in turn facilitates its accessibility to regulatory factors and the transcription and replication machinery. Due to their positive charge they are able to compact DNA (negative charge). Each nucleosome contains approximately 147 base pairs of DNA and several proteins.
Chromatin is the form in which DNA is found in the eukaryotic cell (coiled nucleosomes). Chromatin is composed of a combination of DNA and chromosomal proteins, especially histones, that keep DNA in a compact structure accessible for genetic regulation. Chromatin is a condensed material found in the nucleus of the cell for most of the cell cycle.
It is a condensed and dynamic material that is composed of DNA and chromosomal proteins and plays a key role in the regulation of gene expression and in the equitable distribution of DNA during cell division.
During cell division, chromatin condenses to form chromosomes during cell division, allowing for the equal separation and distribution of DNA to daughter cells.
These are long and elongated structures that can be visualized with an optical microscope during a very specific point in the cell cycle, the cell division.
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