Deoxyribonucleic acid DNA is critically important because it serves as the blueprint for life. It contains the instructions necessary for the growth, development, functioning, and reproduction of all living organisms. In this article, we detail what the hereditary molecule looks like and why is the DNA important.
Structure of DNA
DNA is a double helix made up of nucleotides, which can be called the building blocks of the hereditary molecule. There are only 4 varieties of nucleotides: adenine, guanine, thymine and cytosine. Nucleotides consist of a nitrogenous base, deoxyribose and a phosphoric acid residue. They are related to each other in a complementary way. According to this principle, adenine in one chain always interacts with thymine in another, and vice versa. Similarly, guanine in one chain always interacts with cytosine in another chain. Such base pairs are held together by the formation of hydrogen bonds between them: the A-T pair forms 2 hydrogen bonds, the G-C pair forms 3 hydrogen bonds.
All DNA must double before the cell divides. This process is called DNA replication. The process of replication takes place in the nucleus and ensures the accurate transmission of genetic information from one generation to the next. This process involves 15-20 different proteins-enzymes: for example, in humans, it is necessary to double 3 billion based paired nucleotides of each chain.
In eukaryotic cells (animals, plants and fungi), DNA is located in the cell nucleus as part of chromosomes and in some cell organelles (mitochondria and plastids). In the cells of prokaryotic organisms (bacteria and archaea), a circular or linear DNA molecule, the so-called nucleoid, is attached internally to the cell membrane. Eukaryotic DNA is compactly packed into chromosomes. Humans have 23 pairs of chromosomes: 22 autosomes and one pair of sex chromosomes. One chromosome of the pair is copied from the paternal organism and the other from the maternal organism, and each stores its own genetic information. The last pair, made up of sex chromosomes, determines a person’s sex.
DNA and genetic information
Why is DNA important? DNA carries the genetic information that determines the unique characteristics of every organism. This information is encoded in the sequence of its nucleotide bases (adenine, thymine, cytosine, and guanine), which form specific genes. DNA molecules regulate all cellular processes by controlling which genes are expressed (turned on or off) in specific cells at specific times. This gene regulation ensures that cells perform their specialized functions, such as muscle contraction or nerve signaling.
DNA directs the synthesis of proteins, which are essential for the structure, function, and regulation of the body’s cells, tissues, and organs. The sequence of amino acids in each protein is determined by the sequence of nucleotides in the gene, the section of DNA that codes for that particular protein.
DNA is passed from parents to offspring, ensuring the transmission of genetic traits. This inheritance allows for the continuation of species and the variation within populations, which is fundamental for evolution and adaptation. Each person gets 50% of their genome from their mum and 50% from their dad. But exactly which areas we get from mum and dad is determined randomly for each child. You could say that we are a mosaic of our parents’ genomes.
Mutations in DNA
Sometimes mistakes are made when doubling DNA. Such irregularities are quickly detected by special enzymes and corrected. But sometimes they remain and become mutations – changes in the sequence of the DNA molecule. Mutations are random, non-directional in nature. They lead to the appearance of various traits in individuals, which can be both useful, neutral and harmful to the individual.
Mutations or changes in DNA sequences over time provide the raw material for evolution. These variations can lead to new traits that may give organisms a survival advantage, driving natural selection and biodiversity. Mutations create the basis for the action of a directional factor of evolution – natural selection. In the course of this process, individuals with useful traits that help them adapt to environmental conditions and contribute to their survival remain and reproduce, while individuals without these traits survive less often and do not continue the lineage.
Mutations can lead to the development of genetic diseases. These can be gene (due to a change in a gene), chromosomal (due to a change within a chromosome), genomic (due to a change in the number of chromosomes), or multifactorial (both genetic and environmental factors contribute) diseases. They may be due to mutations inherited in families or to mutations newly arising in germline cells, in the zygote or at very early stages of development. Examples include cystic fibrosis, Down syndrome. phenylketonuria, spian muscular atrophy and others.
DNA is fundamental to life because it encodes the instructions for biological processes, ensures heredity, enables evolution, and serves as a cornerstone for advancements in medicine, agriculture, and biotechnology. A strand of DNA (a double helix) is incredibly stable, allowing it to reliably store genetic information. At the same time, its ability to undergo mutations enables adaptability, which is essential for evolution and survival in changing environments.
