55 Interesting Facts About DNA

In 1869, Friedrich Miescher was the first person to isolate nucleic acid from pus cells found on surgical bandages. He named his discovery as "nuclein", which is now known as DNA.

DNA is the biological molecule that is responsible for the development and functioning of each unique living thing on this planet. It codes for the physical as well as physiological processes of all organisms. In other words, it is the blueprint of life.

DNA also forms the genetic hereditary unit that causes the passing of certain characteristics from parents to their progeny.  Despite such a vast and diverse function, the DNA molecule is composed of various variations of just 4 basic units, called nucleotides or DNA bases.

They are adenine (A), guanine (G), cytosine (C), and thymine (T). Juxtapositions in the sequence of their occurrence has given rise to the plethora of biological species observed in the world.
Few scientists believe that the early Earth developed certain environmental conditions that gave rise to something called a "primordial soup".

This liquid, supposedly, contained the basic building blocks, that merged to form the first life-form on the planet. Another theory suggests that life forms arrived on the planet via meteorites and then thrived and evolved on earth.

These theories are, however, highly contested, and scientists are still unclear about the origin of DNA and life. While the origins remain unclear, scientists have managed to decipher a great deal about this vital molecule.

❖ DNA consists of a double helical structure, resembling a twisted ladder. The steps of the ladder are made of the nucleotide base pairs while the sides are composed of deoxyribose sugars linked to each other with phosphodiester bonds.

❖ It possesses a negative charge due to the presence of phosphate groups.

❖ Experiments carried out by Alfred Hershey and Martha Chase in 1952 helped confirm that DNA is the genetic material in organisms.

❖ Its chemical structure was discovered by James Watson and Francis Crick in 1953, based on the experimental data of Rosalind Franklin and Maurice Wilkins.

❖ The 1958 experiment by Matthew Meselson and Franklin Stahl helped prove that the method of DNA replication was semi-conservative.

❖ The double helical strands are 20-26 Å wide, and each nucleotide unit is 3.3 Å wide. The structure shows a major groove and a minor groove.

❖ This molecule has three structural forms: A form, B form and Z form. The A and B forms are double helices, and differ only in the orientations of their spiral. The Z DNA has a structure similar to the β pleated structure found in protein molecules.

❖ The B DNA structure is found in the genome of most organisms.

❖ Separation of the two strands, on heating, is called denaturation, and denatured and natural DNA have different absorption wavelengths.

❖ DNA sequences have a 5' and a 3' end, and replication always occurs in the 5' to 3' direction.

❖ Sequences of DNA giving rise to a functional unit are called genes. Coding parts of the gene are called exons, and the non coding regions are called introns.

❖ DNA is transcribed into RNA, which is finally translated into proteins. This is the central dogma of molecular biology.

❖ Sets of 3 nucleotides are called codons, and they represent various amino acids.

❖ Any changes in the original DNA sequence are called mutations, and they can be caused by UV radiations, chemicals, environmental factors, etc.

❖ Mutations may change a single nucleotide or stretches of nucleotide sequences.

❖ Mutation may or may not be harmful, depending on the protein that they code for. While some mutations give rise to different physical characteristics, few others give rise to health disorders.

❖ The strands form a beaded structure by being wound on octamers of histone proteins. This structure undergoes re-coiling to form a spiral structure called solenoid. The solenoids are arranged and condensed around itself with the help of scaffolding proteins. This highly condensed structure is called a chromosome.

❖ The chromosome number varies across different species but remains constant for a species. Humans have 46 chromosomes.

❖ The number of copies of chromosomes contained in a cell is called the ploidy of that cell. Cells with two copies of chromosomes are called diploids, ones with three copies are called triploids, and so on. Humans are diploid organisms.

❖ All the chromosomes of an organism, collectively, forms its genome.

❖ In 2003, the Human Genome Project accomplished its goal of deciphering the entire sequence of the human genome.

❖ Genes can be selectively activated or deactivated, and are subject to environmental conditions and cellular stimuli.

❖ Genetic makeup is called the genotype of an organism, while its physical manifestation is called the phenotype.

❖ The rules for genetic interactions and heredity were laid down by Gregor Mendel, based on his experiments on the varieties of pea plants.

❖ A child receives 50% of its genome from each parent, and the genome of the progeny is approximately 95% similar to that of its parents.

❖ The genome of siblings is 98% similar, whereas it is 100% similar in case of twins.

❖ All human beings share 99.9% of their genome sequence. Only 0.1% of genetic difference is responsible for the variations in physical appearance, race, and ethnicity.

❖ The human genome is 3 billion letters long, and is composed of 30,000 genes.

❖ The mitochondria of cells have their own DNA which is replicated independent of the nuclear DNA. It follows a conservative maternal inheritance.

❖ DNA can be isolated from a variety of samples, including, dead skin, hair follicles, blood, sweat, urine, saliva, etc.

❖ Similarities in genetic codes between related individuals, helps establish genealogical maps.

❖ The complete human genome would occupy a space of 3 gigabytes on a computer storage device.

❖ If one were to continuously recite all the bases of the human genome, with no breaks in between, it would last 52 years. While typing it for 8 hours a day at the speed of 60 words per minute, would require 50 years to completely type each letter.

❖ The completed human genome sequence was published on the 50th anniversary of the discovery of the DNA structure by Watson and Crick.

❖ Humans have 1-4% Neanderthal DNA, while we have a 94%-98% genetic similarity with chimpanzees.

❖ Genes make up only 3-5% of the entire genome of an organism.

❖ The International Space Station possesses a copy of the genome of famous and important people like Stephen Hawking and Lance Armstrong, so as to be able to resurrect humanity in the event of an apocalyptic destruction of the planet.

❖ The first viable cloned organism was a sheep named "Dolly" who was cloned by inserting the nuclear material of one female sheep into the egg cell of another female sheep.

❖ According to a Harvard study, a single gram of DNA can store 700 terabytes of data in totality.

❖ When an organism shows presence of two sets of DNA, it is called a chimera. It usually occurs due to fusion of multiple fertilized eggs during embryogenesis or as a result of organ or bone marrow transplant.

❖ Due to the use of nuclear weapons in World War II, people born after 1955 have trace amounts of radioactive carbon in their DNA.

❖ Mitochondrial DNA can be used to determine maternal ancestry.

❖ The egg and the sperm cells are the only haploid cells in the human body.

❖ Genetic screening of the genome can help in identifying disease risks.

❖ The DNA mapping system used by law agencies is called CODIS (Combined DNA Index System), identifies DNA samples by locating and recognizing 13 conserved loci on the human genome.

❖ Many countries like the US and the UK, maintain a genetic database of the genomes of convicted criminals.

❖ DNA analysis is used to verify the authenticity of foods like caviar and wine.

❖ The genetic material can be modified to produce genetically modified plants and microbes.

❖ DNA can be replicated in vitro using the technology of polymerase chain reaction (PCR).

❖ The Hornsleth Deep Storage Project aims to place a structure containing the genetic samples of humans, animal, and plants, into the Mariana trench for preservation, so as to be able to resurrect endangered species, and humans, if required, in the future.

❖ DNA has an approximate half-life of about 521 years. This implies that the oldest DNA samples that can be cloned cannot be older than 2 million years.

❖ Approximately 8% of the human genome contains residual sequences of viral genome, from the viruses that infected our ancestors.

❖ A team of scientists have successfully incorporated the lyrics of the song "It's a Small World After All" into the genome of a bacterium, with the aim of developing a method to pass on messages for future intelligent life forms.

❖ Bdelloid rotifers are ancient aquatic animals with the ability to absorb foreign DNA and add new characteristics to its own genome from the newly acquired genetic material. It has evolved over the years to develop the ability to survive for as long as 9 years of desiccation.

❖ An organism's DNA undergoes 1 million events of damage per cell everyday. These damages are constantly corrected by the damage repair pathways of the cell.

Ongoing extensive research will open up new avenues of manipulating the genetic makeup of an organism that can prove beneficial to the human race. In the near future, it may be possible to eradicate all diseases, evade aging, or even store memories. The possibilities are truly endless.