When was genetics first discovered

DNA is made up of molecules known as nucleotides. Each nucleotide contains a sugar and phosphate group as well as nitrogen bases.

These nitrogen bases are further broken down into four types, including:. The sugar and phosphates are nucleotide strands that form the long sides. The nitrogen bases are the rungs. Every rung is actually two types of nitrogen bases that pair together to form a complete rung and hold the long strands of nucleotides together. Remember, there are four types of nitrogen bases, and they pair together specifically — adenine pairs with thymine, and guanine with cytosine.

Human DNA is unique in that it is made up of nearly 3 billion base pairs, and about 99 percent of them are the same in every human. Think of DNA like individual letters of the alphabet — letters combine with one another in a specific order and form to make up words, sentences, and stories.

The same idea is true for DNA — how the nitrogen bases are ordered in DNA sequences forms the genes, which tell your cells how to make proteins. Ribonucleic acid RNA , another type of nucleic acid, is formed during the process of transcription when DNA is replicated. DNA is essentially a recipe for any living organism. During this process, DNA unwinds itself so it can be replicated.

RNA acts as a messenger, carrying vital genetic information in a cell from DNA through ribosomes to create proteins, which then form all living things. DNA was discovered in by Swiss researcher Friedrich Miescher, who was originally trying to study the composition of lymphoid cells white blood cells. Instead, he isolated a new molecule he called nuclein DNA with associated proteins from a cell nucleus. While Miescher was the first to define DNA as a distinct molecule, several other researchers and scientists have contributed to our relative understanding of DNA as we know it today.

The full answer to the question who discovered DNA is complex, because in truth, many people have contributed to what we know about it.

DNA was first discovered by Friedrich Miescher, but researchers and scientists continue to expound on his work to this day, as we are still learning more about its mysteries. Watson and Crick contributed largely to our understanding of DNA in terms of genetic inheritance, but much like Miescher, long before their work, others also made great advancements in and contributions to the field.

The future of DNA has great potential. DNA insights are already enabling the diagnosis and treatment of genetic diseases. Science is also hopeful that medicine will advance to be able to leverage the power of our own cells to fight disease. For example, gene therapy is designed to introduce genetic material into cells to compensate for abnormal genes or to make a therapeutically beneficial protein.

Researchers also continue to use DNA sequencing technology to learn more about everything from combating infectious disease outbreaks to improving nutritional security. Miescher thus made arrangements for a local surgical clinic to send him used, pus-coated patient bandages; once he received the bandages, he planned to wash them, filter out the leukocytes, and extract and identify the various proteins within the white blood cells. But when he came across a substance from the cell nuclei that had chemical properties unlike any protein, including a much higher phosphorous content and resistance to proteolysis protein digestion , Miescher realized that he had discovered a new substance Dahm, Sensing the importance of his findings, Miescher wrote, "It seems probable to me that a whole family of such slightly varying phosphorous-containing substances will appear, as a group of nucleins, equivalent to proteins" Wolf, More than 50 years passed before the significance of Miescher's discovery of nucleic acids was widely appreciated by the scientific community.

For instance, in a essay on the history of nucleic acid research, Erwin Chargaff noted that in a historical account of nineteenth-century science, Charles Darwin was mentioned 31 times, Thomas Huxley 14 times, but Miescher not even once. This omission is all the more remarkable given that, as Chargaff also noted, Miescher's discovery of nucleic acids was unique among the discoveries of the four major cellular components i.

Meanwhile, even as Miescher's name fell into obscurity by the twentieth century, other scientists continued to investigate the chemical nature of the molecule formerly known as nuclein. One of these other scientists was Russian biochemist Phoebus Levene. A physician turned chemist, Levene was a prolific researcher, publishing more than papers on the chemistry of biological molecules over the course of his career.

Levene is credited with many firsts. For instance, he was the first to discover the order of the three major components of a single nucleotide phosphate-sugar-base ; the first to discover the carbohydrate component of RNA ribose ; the first to discover the carbohydrate component of DNA deoxyribose ; and the first to correctly identify the way RNA and DNA molecules are put together.

During the early years of Levene's career, neither Levene nor any other scientist of the time knew how the individual nucleotide components of DNA were arranged in space; discovery of the sugar-phosphate backbone of the DNA molecule was still years away. The large number of molecular groups made available for binding by each nucleotide component meant that there were numerous alternate ways that the components could combine. Several scientists put forth suggestions for how this might occur, but it was Levene's "polynucleotide" model that proved to be the correct one.

Based upon years of work using hydrolysis to break down and analyze yeast nucleic acids, Levene proposed that nucleic acids were composed of a series of nucleotides, and that each nucleotide was in turn composed of just one of four nitrogen-containing bases, a sugar molecule, and a phosphate group.

Levene made his initial proposal in , discrediting other suggestions that had been put forth about the structure of nucleic acids. In Levene's own words, "New facts and new evidence may cause its alteration, but there is no doubt as to the polynucleotide structure of the yeast nucleic acid" Indeed, many new facts and much new evidence soon emerged and caused alterations to Levene's proposal.

One key discovery during this period involved the way in which nucleotides are ordered. Levene proposed what he called a tetranucleotide structure, in which the nucleotides were always linked in the same order i. However, scientists eventually realized that Levene's proposed tetranucleotide structure was overly simplistic and that the order of nucleotides along a stretch of DNA or RNA is, in fact, highly variable. Despite this realization, Levene's proposed polynucleotide structure was accurate in many regards.

For example, we now know that DNA is in fact composed of a series of nucleotides and that each nucleotide has three components: a phosphate group ; either a ribose in the case of RNA or a deoxyribose in the case of DNA sugar; and a single nitrogen-containing base. We also know that there are two basic categories of nitrogenous bases: the purines adenine [A] and guanine [G] , each with two fused rings, and the pyrimidines cytosine [C], thymine [T], and uracil [U] , each with a single ring.

Erwin Chargaff was one of a handful of scientists who expanded on Levene's work by uncovering additional details of the structure of DNA, thus further paving the way for Watson and Crick. Chargaff, an Austrian biochemist, had read the famous paper by Oswald Avery and his colleague s at Rockefeller University, which demonstrated that hereditary units, or genes , are composed of DNA.

This paper had a profound impact on Chargaff, inspiring him to launch a research program that revolved around the chemistry of nucleic acids. Of Avery's work, Chargaff wrote the following:. Avery gave us the first text of a new language, or rather he showed us where to look for it.

I resolved to search for this text. As his first step in this search, Chargaff set out to see whether there were any differences in DNA among different species. After developing a new paper chromatography method for separating and identifying small amounts of organic material, Chargaff reached two major conclusions Chargaff, First, he noted that the nucleotide composition of DNA varies among species.

In other words, the same nucleotides do not repeat in the same order, as proposed by Levene. Second, Chargaff concluded that almost all DNA--no matter what organism or tissue type it comes from--maintains certain properties, even as its composition varies. In particular, the amount of adenine A is usually similar to the amount of thymine T , and the amount of guanine G usually approximates the amount of cytosine C. This second major conclusion is now known as "Chargaff's rule. Watson and Crick's discovery was also made possible by recent advances in model building, or the assembly of possible three-dimensional structures based upon known molecular distances and bond angles, a technique advanced by American biochemist Linus Pauling.

In fact, Watson and Crick were worried that they would be "scooped" by Pauling, who proposed a different model for the three-dimensional structure of DNA just months before they did.

In the end, however, Pauling's prediction was incorrect. Using cardboard cutouts representing the individual chemical components of the four bases and other nucleotide subunits, Watson and Crick shifted molecules around on their desktops, as though putting together a puzzle.

They were misled for a while by an erroneous understanding of how the different elements in thymine and guanine specifically, the carbon, nitrogen, hydrogen, and oxygen rings were configured. Only upon the suggestion of American scientist Jerry Donohue did Watson decide to make new cardboard cutouts of the two bases, to see if perhaps a different atomic configuration would make a difference.

It did. Not only did the complementary bases now fit together perfectly i. Figure 3: The double-helical structure of DNA. Complementary bases are held together as a pair by hydrogen bonds. Figure Detail. Although scientists have made some minor changes to the Watson and Crick model, or have elaborated upon it, since its inception in , the model's four major features remain the same yet today.

These features are as follows:. One of the ways that scientists have elaborated on Watson and Crick's model is through the identification of three different conformations of the DNA double helix. In other words, the precise geometries and dimensions of the double helix can vary.

The most common conformation in most living cells which is the one depicted in most diagrams of the double helix, and the one proposed by Watson and Crick is known as B-DNA. There are also two other conformations: A-DNA , a shorter and wider form that has been found in dehydrated samples of DNA and rarely under normal physiological circumstances; and Z-DNA, a left-handed conformation. Z-DNA was first discovered in , but its existence was largely ignored until recently. Watson and Crick were not the discoverers of DNA, but rather the first scientists to formulate an accurate description of this molecule's complex, double-helical structure.

Moreover, Watson and Crick's work was directly dependent on the research of numerous scientists before them, including Friedrich Miescher, Phoebus Levene, and Erwin Chargaff.

Thanks to researchers such as these, we now know a great deal about genetic structure, and we continue to make great strides in understanding the human genome and the importance of DNA to life and health.

Chargaff, E. Chemical specificity of nucleic acids and mechanism of their enzymatic degradation. Experientia 6 , — They conclude that hereditary information is contained within chromosomes. US scientist Thomas Hunt Morgan is the first to discover a sex-linked trait, while studying the fruit fly Drosophila.

The trait for eye colour, on the X chromosome, is also the first gene to be traced to a specific chromosome. A trio of US geneticists revisit work from the s and prove that, in bacteria, DNA is the hereditary material, and not protein as was previously suspected. They are awarded a Nobel prize in for their efforts. Crick and South African geneticist Sydney Brenner report that trios of DNA bases — called nucleotides — each hold the instructions for one of the 20 amino acids that combine to form proteins.

US researcher Herb Boyer uses enzymes to cut DNA and splice it into bacterial plasmids, which then replicate producing many copies of the inserted gene. This heralds the dawn of genetic engineering. The international Human Genome Project begins, with the goal of sequencing the entire human genetic code.