Initiator RNA
See iRNA.

Initiator tRNA
A tRNA molecule that carries the amino acid methionine and initiates translation.

Innate immune response
Immune response that involves the preexisting defences of the body. These include the barriers formed by the skin and mucosa, antimicrobial molecules and phagocytes. This type of immune response is however not specific for the pathogen.

Innate immunity
Immunity present from birth and not based on prior antigen exposure. The components of innate immunity include physical and chemical barriers to infection, phagocytes, complement, and NK cells.

Inoculate
Deliberate introduction. It is not however synonymous to contamination. 1. In microbiology and tissue culture, refers to placing inoculum into (or onto) medium in order to initiate a culture. 2. In immunology, to immunize.

Inoculation
Introduction of a small of a microorganisms into a new environment such as inoculation of fermenters. The small dose of the organism introduced is termed the inoculant.

Inoculation cabinet
A small room or cabinet where inoculation of tissue or microorganism culture is done. This chamber is equipped with a current of sterile air to carry contaminants away from the work area.

Inoculum
(pl: inocula). 1. A small piece of tissue cut from a tissue or organ, or a small amount of cell material from a suspension culture that is transferred into fresh medium for continued growth of the culture. 2. Microbial spores or components such as mycelium. 3. Vaccine.

Inomics
The study of inositol signaling molecules (ISMs) and their role in regulating cellular functions.

Inorganic compound
A chemical compound that is not derived from living material; compounds that do not contain carbon.

Inorganic pyrophosphatase
An enzyme that hydrolyses inorganic phrophosphate to yield two molecules of orthophosphate. Also termed pyrophosphatase.

Inorganic sulphur
An index of protein catabolism. It is a completely oxidised from of sulphur that precipitates from urine on addition of barium chloride.

Inosine
A purine base present in inosine monophosphate (IMP), the precursor of AMP and GMP.

Inositol
(hexahydroxycyclohexane; C6H6(OH)6) 1. A cyclic acid, which is a component of some phosphoglycerides. 2. A water-soluble nutrient that is considered as a “vitamin” in plant tissue culture. Also functions as a growth factor in some animals and microorganisma.

Inositol lipid
A membrane-bound phospholipid that transduces hormonal signals by inducing the release of any of several chemical messengers.

Inositol triphosphate
A second messenger in lymphocyte activation that increases intracellular calcium and activates calcineurin.

Insecticide
A substance or living organism that kills insects.

Insert
A DNA molecule incorporated into a cloning vector.

Insertion
1. The presence of additional base pairs in DNA. 2. A part of a sequence alignment where one sequence appears to have extra monomers compared to another sequence.

Insertion element
A term used to refer to DNA sequences found in bacteria that are capable of getting inserted into the genome. It is hypothesised to be responsible for site-specific phage and plasmid integration.

Insertion mutations
Changes in the base sequence of DNA that result form the random integration of DNA from another source.

Insertion sequence (IS)
A short DNA sequence (800-1400 base pairs) found in a bacterium that is capable of inserting itself or a copy of it into another DNA molecule. It carries information only for transposition.

Insertion site; cloning site
A unique site in a vector DNA molecule that can be cleaved by a restriction endonuclease in order to incorporate a foreign DNA molecule. The term is also used to refer to the position of integration of a transposon or insertion site element.

Insertion vector
A bacteriophage lambda vector into which a foreign DNA can be inserted by cleavage at a single site.

Insertional inactivation
The loss of gene expression that results when a DNA segments in cloned into a region of a vector molecule that is critical for expressing the gene. For example, insertion of a DNA segment into the antibiotic resistance gene of a plasmid vector abolished resistance to that antibiotic. This phenomenon is used in the selection of recombinants from nonrecombinant clones.