DNA is found both in prokaryotes and eukaryotes. In prokaryotes, DNA is double stranded and circular and is found throughout the cytoplasm called nucleoid. In eukaryotes, DNA is located in nucleus and in mitochondria or chloroplasts.

Variation allows some individuals within a population to adapt to the changing environment. Because natural selection acts directly only on phenotypes, more genetic variation within a population usually enables more phenotypic variation.

The term 'plasmid' was coined by Joshua Lederberg in 1952, referring to the extrachromosomal DNA of an organism. It is the extrachromosomal DNA of an organism capable of self-replication as well as horizontal transfer, and confers certain characteristics to the bacterium, such as antibiotic resistance, etc.

Trypsin is a pancreatic serine protease that is involved in the breakdown of dietary protein molecules into peptides. Pancreas, a accessory digestive organ is made up of small clusters of glandular epithelial cells.

Cytochemical staining method for nucleic acid depends on the properties of nucleic acid components or nucleotides. DNA can be studied by means of the nuclear reaction,a technique developed by Feulgen and Rossenbeck.

Solutions of short chain alcohols and acetic acid have been commonly used for fixing proteins as insoluble aggregates within gel matrix. The combination of low pH and high organic solvent content disrupts the hydrogen bonding which holds protein structures together, and exposes hydrophobic portions of the protein core.

The Periodic Acid Schiff, or PAS reaction is a technique for the demonstration of presence of carbohydrates. McManus devised the technique based on selective oxidation of “1,2 glycol” group on monomer unit of all insoluble polysaccharides by Periodic Acid (HIO4) with liberation of aldehyde group which on reaction with Schiff’s reagent form a magenta coloured complex.

Mitosis is a type of cell division in which one cell (the mother) divides to produce two new cells (the daughters) that are genetically identical to itself. In the context of the cell cycle, mitosis is the part of the division process in which the DNA of the cell's nucleus is split into two equal sets of chromosomes