DNA is the molecule which contains biological instructions that form every species different from one other. It can be transferred from one generation to another.
Discovery of DNA
Swiss biochemist Frederich Miescher first saw DNA in late 1800. For many years, scientists debated on the process of transferring of biological instructions. The basic concept of DNA was cleared in 1953 by James Watson, Francis Crick, Maurice Wilkins and Rosalind Franklin. Double helical structure of DNA is discovered by studying X-ray diffraction patterns and building models.
Where is DNA found?
In eukaryotes, it is found in the nucleus. DNA is very tightly because the size of the cell is very small and there is number of DNA in a cell. So it has to be densely packed. And this condensed form of DNA is known as Chromosome.
- During DNA replication, unwinding of DNA is done so it can easily make its copies. In other stages, unwinding can also happen so that it can be used to make proteins and for other biological processes. During cell division, compact form of DNA is seen so that it can be transferred to new cells.
- The DNA is also called as nuclear chromosome and the total set of nuclear DNA is called as the genome.
- Other than humans, DNA is located in mitochondria also in some complex organisms. Energy is created by mitochondria for proper functioning of the cell.
- In sexual reproduction, half of the nuclear DNA is transferred from male parent and half from the female parent to the new organism.
- However, mitochondrial DNA is fully transferred from female parent to the new organism. This is done because during reproduction only egg cells keep their mitochondria during fertilization.
What is DNA made of?
The basic and structural unit of DNA is nucleotides. Nucleotide is made up of 3 components: a phosphate group, a sugar group and one of the 4 types of nitrogen bases. For the formation of a chain of DNA, these nucleotides are connected together into the form of a chain, with alteration of phosphate and sugar groups.
- 4 types of nucleotides are adenine (A), thymine (T), guanine (G) and cytosine (C). The sequences of nucleotides are arranged for particular biological instructions.
- The genome of a human contains about 3 million bases and about 20,000 genes on 23 pairs of chromosomes.
Function of DNA
For the development of an organism, DNA is required because it contains all the necessary instructions needed for the development. For such developmental process, DNA must be converted into messages so that it can be used for the production of proteins.
- Every DNA sequence that contains information for the production of protein is known as gene. The size of gene varies from very small to medium; it ranges from 1,000 bases to 1 million bases in humans.
- Makeup of 1% of DNA sequence is done by genes only.
- Remaining sequence of DNA is involved in regulation of formation of protein when, how and how much protein is made.