What is DNA? DNA from Yesterday to Today!

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Deoxyribonucleic acid, or abbreviated DNA: is a molecule that contains the instructions an organism needs to develop, live, and reproduce. These instructions are found in each cell and passed on to descendants.


DNA consists of molecules called nucleotides. Each nucleotide contains a phosphate group, a sugar group, and a nitrogen base. The nitrogen base includes adenine (A), thymine (T), guanine (G), and cytosine (C). The order of these bases determines the instructions or genetic code of the DNA. According to the US National Library of Medicine, there are about 3 billion bases in human DNA, and more than 99 percent of these bases are the same in all humans.

The bases in DNA are somewhat like the alphabet; we form words with letters. In DNA, on the other hand, bases show cells how to produce proteins. Ribonucleic acid, or short for RNA, transfers the information from DNA to proteins.

Two long strands of nucleotides come together to form a structure called a double helix. If we give an example with a double-helix ladder: phosphate and sugar molecules become handrails, bases become steps. Bases in one set match with bases in the other set, but this match is anti-parallel so one side is upside down. Likewise, matches are also complementary. The base in each strand ties only one base from another strand.

DNA molecules are also very long structures. So much so that if they are not placed properly, they may not fit into the cells. The DNA is tightly coiled to ensure correct placement, forming the chromosome. Humans have 23 pairs of chromosomes, and these chromosomes are located in the nuclei of the cell.


DNA was first observed in 1869 by a German biochemist named Frederich Miescher. However, for many years the importance of this molecule was not understood by researchers. In 1953, James Watson, Francis Crick, Maurice Wilkins, and Rosalind Franklin formulated the structure (double helix) of DNA, which they realized could carry biological information

Watson, Crick, and Wilkins were awarded the Nobel Prize in Medicine in 1962 for their “discovery of the molecular structure of nucleic acids and the importance of knowledge transfer in living things”. Indeed, he does
Franklin was not included in the award, although the studies were an integral part of the research.


DNA sequencing is a technology that allows researchers to determine the order of bases in a DNA sequence. This method can be used to determine the order of bases in genes, chromosomes, or genome. According to the report published by the US National Human Genome Research Institute in 2000, the researchers have completed the sequencing of the human genome.


There is information about the genetic inheritance in the DNAs of the people and it can be determined whether a person is at risk against certain diseases or not through these DNAs. DNA tests or genetic tests can be done for a variety of purposes, such as diagnosing inherited diseases, determining whether the individual has a genetic mutation carrier that can be passed on to inferior lineage, or whether he or she is at risk for an inherited disease.

For example, mutations in the BRCA1 and BRCA2 genes, which are known to increase the risk of breast and ovarian cancer in a person, can be detected through genetic testing. The results of genetic tests may also have some effects on the health of the people who have them done. For this reason, genetic testing is often provided with test counseling to help test takers understand their results.

There are many test kits we can do in our homes today, but not all of them are completely reliable. Likewise, special attention should be paid to these tests, as these tests require the person to have the test to give their genetic code to a stranger.


As a result of DNA research, several interesting and important findings have been discovered in the last few years. For example, according to a study published in Journal Science in 2017, it was revealed that two-thirds of cancer mutations do not occur due to environmental or hereditary reasons, rather they are caused by random errors in DNA.

Another important piece of news from 2017 is the first DNA sequencing on Egyptian mummies. “We are very excited to have sequenced the genome of ancient Egyptian mummies,” said Stephan Schiffels, Group Leader of Population Genetics at the Max Planck Institute for the Science of Human History in Jena, Germany.
The findings of the research were shared in the May 2017 issue of Nature Communications. One month after this study on Egyptian mummies, film pixels were processed into human DNA. Researchers used DNA as pixels during the study.

“We are thinking of a biological memory system that will be smaller and more efficient than today’s technologies, so we want to turn cells into a kind of chronicler,” said Seth Shipman of Harvard Medical School in Boston, USA. Their findings were published in the July 2017 issue of Nature magazine.