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DNA: DEOXYRIBONUCLEIC ACID
What is DNA?
Deoxyribonucleic acid or DNA is a molecule which carries the genetic instructions or the hereditary material which is used in the growth and development of all known living organisms including viruses.
DNA is found in all living organisms. This nucleic acid is mainly responsible for the inheritance among the human beings. The cells of the human body possess same DNA which is located in the nucleus of cells hence it is described as nuclear DNA and the DNA present in the mitochondria is termed as mitochondrial DNA which is inherited from the mother to their children. In humans, there are approximately 16,000 base pairs of mitochondrial DNA.
DNA was first recognized and identified by Swiss biologist named Johannes Friedrich Miescher in the year 1869. The double helix structure of a DNA molecule was later discovered through the experimental data by James Watson and Francis Crick. Finally, it was proved that the DNA is responsible for storing the biological information of a human being.
DNA is a double helix structure that resembles a ladder as shown in the figure below, which is twisted at both the ends. The DNA molecule is made up of basic materials called as nucleotides and each nucleotide is made up of three different components naming sugar, phosphate groups, and nitrogen bases.
Among the 3 components of DNA, the sugar is the one which forms the backbone of the DNA molecule. It is also called to as deoxyribose.
The phosphate group is compound forming a carbon chain or a regular ring pattern in the form of a ladder. This chain comprises of phosphorous which in turn is attached to 4 molecules of oxygen.
DNA molecule consists of 4 nitrogen bases namely adenine (A), thymine (T), cytosine
(C) and Guanine (G). which completely forms the structure of a nucleotide. The A and G from a pair of purines and the C and T from pyrimidines. Both purines and pyrimidines differ as they have the carbon rings either single or double.
The two strands of DNA run in opposite directions. The hydrogen bonds between are responsible for holding the two strands together.
DNA’s are coiled up forming chromosomes and each of chromosome has a single molecule of DNA in it. Overall Human beings have around twenty-three pairs of chromosomes in them. These chromosomes are found inside the cells of the nucleus. The DNA’s play an important role in the process of cell division. It is considered that there are three billion bases in the genetic material called DNA of the human body.
Functions of DNA:
DNA is the genetic material which carries all the hereditary information which is coded in the arrangement of its nitrogen bases. Apart from the hereditary information, DNA is also involved in:
- Replication process: transfer of genetic information from one cell to its daughters and from one generation to the next.
- Equal distribution of DNA during cell division.
- Mutations: changes which occur during DNA sequences.
- Cellular Metabolism.
- DNA Finger Printing.
DNA profiling (also called DNA fingerprinting, DNA testing, or DNA typing) is the process of determining an individual’s DNA characteristics, called a DNA profile, that is very likely to be different in unrelated individuals, thereby being as unique to individuals as are fingerprints (hence the alternative name for the technique). DNA profiling with the aim of identifying not an individual but a species is called DNA barcoding.
DNA profiling is most commonly used as a forensic technique in criminal investigations to identify an unidentified person or whose identity needs to be confirmed, or to place a person at a crime scene or to eliminate a person from consideration. DNA profiling has also been used to help clarify paternity, in immigration disputes, in parentage testing and in genealogical research or medical research. DNA fingerprinting has also been used in the study of animal and floral populations and in the fields of zoology, botany, and agriculture.
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