DNA is the most well-known biological molecule, and it can be found in all kinds of life on the planet. But what exactly is DNA, also known as deoxyribonucleic acid? We will go through the basics here.
DNA, or the genetic information that makes you who you are, is found in almost every cell in your body. All life’s instructions for development, growth, reproduction, and function are encoded in DNA.
Genetic differences explain why some people have blue eyes instead of brown, why certain people are predisposed to particular diseases, why birds have just two wings, and why giraffes have lengthy necks.
Amazingly, if all of the DNA in the human body were unwound, it would stretch more than 300 times around the world.
What is DNA?
The hereditary substance in humans and almost all other animals is DNA, or deoxyribonucleic acid. The DNA of nearly every cell in a person’s body is identical. The majority of DNA is contained in the cell nucleus (also known as nuclear DNA), although a tiny quantity is also present in the mitochondria (where it is called mitochondrial DNA ). Mitochondria are cellular structures that convert food energy into a form that cells can utilize.
Each person’s genetic information is encoded in DNA, which is a lengthy molecule. It contains the instructions for constructing the proteins required for our bodies to function. DNA instructions are passed down from parent to child, with around half of a child’s DNA coming from the father and half from mother.
Structure of DNA
DNA is a two-stranded molecule with a twisted appearance, giving it the shape of a double helix.
Adenine (A), guanine (G), cytosine (C), and thymine (T) are the four chemical bases that make up DNA’s coding (T). Human DNA is made up of around 3 billion bases, with over 99 percent of those bases being identical in all humans. Similar to how letters of the alphabet appear in a specific order to form words and sentences, the arrangement, or sequence, of these bases dictates the information accessible for creating and maintaining an organism.
DNA bases pair up with each other, A with T and C with G, to form units called base pairs. Each base has a sugar molecule and a phosphate molecule connected to it. A nucleotide is made up of a base, sugar, and phosphate. Nucleotides are structured in a spiral known as a double helix, which is made up of two long strands.
The structure of the double helix is similar to that of a ladder, with the base pairs forming the rungs and the sugar and phosphate molecules serving as the ladder’s vertical sidepieces.
One of DNA’s most essential properties is its ability to replicate, or generate copies of itself. Each strand of DNA in the double helix can be used as a template to duplicate the base sequence. When cells divide, this is crucial because each new cell must have a perfect copy of the old cell’s DNA.
The Structure of DNA Provides a Heredity Mechanism
When a cell divides to generate two daughter cells, genes convey biological information that must be precisely duplicated for transmission to the next generation. These criteria raise two important biological questions: how can information for identifying an organism be transported in chemical form, and how is it accurately copied?
The discovery of the structure of the DNA double helix was a watershed moment in twentieth-century biology because it provided instant answers to both issues, resolving the problem of heredity at the molecular level.
The order, or sequence, of the nucleotides along each strand encodes information. Each base—A, C, T, or G—can be thought of as a letter in a four-letter alphabet that translates biological messages into the DNA’s chemical structure. Organisms differ from one another because their DNA molecules have various nucleotide sequences and, as a result, contain diverse biological information.
Genes contain the instructions for creating proteins long before the structure of DNA was discovered. As a result, the DNA signals must encode proteins in some way. Because of the molecular nature of proteins, this link immediately makes the situation more understandable. The features of a protein that are responsible for its biological function are dictated by its three-dimensional structure, which is determined by the linear sequence of the amino acids that make it up.
As a result, the linear sequence of nucleotides in a gene must correspond to the linear sequence of amino acids in a protein in some way. The exact link between the four-letter nucleotide alphabet of DNA and the twenty-letter amino acid alphabet of proteins—the genetic code—is not clear from the DNA structure, and it took more than a decade after the double helix was discovered to figure out. Gene expression, which is the process by which a cell converts a gene’s nucleotide sequence into a protein’s amino acid sequence explains the code properly.
What is a Gene?
A gene is a segment of DNA that codes for a certain protein. One gene, for example, codes for the protein insulin, a hormone that aids in the regulation of blood sugar levels. Although estimates vary, humans have between 20,000 and 30,000 genes.
Our genes make up only about 3% of our DNA; the remaining 97 percent is less well understood. The exceptional DNA is hypothesized to play a role in transcription and translation regulation.
Who Discovered DNA?
Rosalind Elsie Franklin (1920-1958), a British chemist and crystallographer, is well known for discovering the structure of DNA.
According to an article published in 2005 in the Journal of Developmental Biology, Swiss biologist Friedrich Miescher discovered DNA in 1869. Miescher isolated DNA — which he dubbed nuclein — from white blood cells and sperm using biochemical procedures and discovered that it was substantially different from protein. (The word “nucleic acid” comes from the word “nuclein.”)
However, for many years, researchers were unaware of the significance of this molecule.
X-ray diffraction — a method of detecting the structure of a molecule by the way X-rays bounce off it — was employed by chemist Rosalind Franklin, who was working in the lab of biophysicist Maurice Wilkins, in 1952, to discover that DNA had a helical structure. In what became known as Photo 51, Franklin photographed this edifice.
Without Franklin’s knowledge, Wilkins showed the shot to researchers James Watson and Francis Crick in 1953. Watson and Crick published a major 1953 publication in the journal Nature, armed with the knowledge that DNA was a double helix and prior observations that the bases adenine and thymine, as well as guanine and cytosine, were found in equal proportions within DNA.
They suggested the now-iconic double-helix model of DNA, with sugar-phosphate sides and rungs made up of A-T and G-C base pairs, in that publication. They also argued that DNA could be duplicated — and hence passed on — using their proposed structure.
“For their discoveries about the molecular structure of nucleic acids and their significance for information transfer in living material,” Watson, Crick, and Wilkins were given the Nobel Prize in medicine in 1962. Despite the fact that Franklin’s contribution was critical to the research, she did not get an award.
How is DNA Sequenced?
Researchers can establish the order of bases in a piece of DNA using DNA sequencing techniques. The technology can be used to determine the base order in genes, chromosomes, or a whole genome. According to the National Human Genome Research Institute, researchers completed a “working draft” sequence of the human genome in 2000 and completed the project in 2003.
How does DNA Work?
Genes code for proteins that serve a variety of roles in humans (and other living beings). The human gene HBA1 provides instructions for making the protein alpha globin, which is a component of hemoglobin, the oxygen-carrying protein in red blood cells. According to the National Center for Biotechnology Information’s Gene database, the gene OR6A2 encodes an olfactory receptor, a protein that senses odors in the nose. According to a study published in the Journal Flavour in 2012, you may adore cilantro or think it tastes like soap depending on whatever variation of OR6A2 you have.
Despite the fact that each of your 37.2 trillion cells contains a copy of your DNA, not all cells produce the same proteins. One reason for this is that molecules known as “transcription factors” hook onto DNA to control which genes are turned on and off, and hence which proteins are generated when, where, and in what quantities in each cell. In addition, various cell types have slightly varied packaging of DNA, which affects how and where transcription factors can capture the molecule.
Epigenetics, which literally means “above” or “on top of” genetics, refers to exogenous DNA alterations that switch specific genes on or off. Small chemicals known as methyl groups, for example, can bond to a DNA strand and block some genes from being produced. Changes to the spool-like proteins inside chromosomes can make specific portions of DNA more or less accessible to the proteins that “read” genes, which is another form of epigenetics. If epigenetic modifications to DNA occur in sperm or egg cells, they can be passed down to future generations.