What is DNA
DNA stands for Deoxyribonucleic Acid. It is the genetic or hereditary material or molecule or genome that is present in the form of chromosomes in the nucleus of the cells. However, some DNA is also found in the Mitochondria, a cell organelle present in the cell.
DNA contains or carries genetic code or instructions or information for growth, reproduction, development and traits or features or characteristics from organisms to their offspring. It is present in every cell of the body of an organism such as every cell of the human body.
Who discovered DNA?
Swiss biologist, Johannes Friedrich Miescher identified DNA for the first time in 1869 while he was doing research on white blood cells. For many years, scientists were not able to find out more about DNA and about its importance. Later, in 1953, James Watson, Francis Crick, were able to figure out the double helix structure of DNA that could carry genetic information.
Types of DNA
In the cells of eukaryotic organisms like plants, animals, apart from the nucleus, a small amount of DNA is also present in the cell organelle such as in mitochondria. So, based on the location, DNA can be of the following two types:
Forms of DNA I Structural Conformations of DNA
DNA is a long polymer of nucleotides. It can assume different types of structural conformations based on various factors such as salt concentration, hydration level, DNA sequence, presence of chemically modified bases, etc.
The DNA as revealed by the classic Watson - Crick Model is known as B-DNA or B-form DNA. Under certain conditions, DNA can attain various other forms or conformations, some of which are described below:
The common structural conformations of DNA are described below:
It is a rare type of DNA conformation that is adopted by DNA during dehydration conditions. Although it also has a double-stranded helical structure like B-DNA, it is shorter and has a compact structural organization. Structural features of A-DNA are given below:
This form of DNA is the Watson-Crick double helix model of DNA that most people are familiar with. It is the most common DNA conformation or form in which DNA occurs under the natural physiological conditions such as salt concentration and pH in the cell. Some of the important structural features of B-DNA are given below:
It is formed when the DNA has an alternating purine-pyrimidine sequence such as GCGCGC. Besides this, in this sequence the G and C nucleotides have different conformations that gives it a zig-zag pattern. The G nucleotide has sugar in the C3' endoconformation like A-DNA and unlike B-DNA, whereas the guanine base is in the synconformation due to this reason the Guanine is located over the sugar ring unlike normal anticonformation as found in A and B form of DNA.
Some of the major structural features of Z-form DNA are follows:
Functions of DNA: