Bradykinin See kinins.

Branching Enzyme (amylo[1®4]®[1®6] transglucosidase) The enzyme that catalyses branching of the glycogen molecule, in which a part of the chain consisting of six glucose residues is transferred to a neighbouring chain establishing a branch point with α1® 6 linkage.

Bragg’s law During diffraction of x-rays by crystals, each diffracted beam can be considered to be reflected from a set of parallel lattice planes. Bragg’s  law states that nλ=2dsinθ. When x-rays strike a crystal, they will be diffracted only if this equation is satisfied.

Branchpoint An intermediate in a biochemical pathway that can be channeled into two or more biochemical pathways.

BRCA1, BRCA2 genes The breast  cancer susceptibility genes suggested to be key genes involved in the development of familial breast cancer. BRCA1 is located on chromosome 17q21. It encodes a large protein containing 1863 amino acids that may function as a transcription factor. BRCA2 mapped to chromosome 13q12-13, encodes a protein of 3495 amino acids. The BRCA proteins, which regulate cell cycle arrest, apoptosis and DNA repair, function as central gatekeepers of genomic stability. Mutations in the BRCA1 gene in breast and ovarian tumours cause loss or truncation of th Ebrca1 transcript. Carries of mutations in BRCA1 and BRCA2 are estimated to have an enchanced lifetime risk of developing breast cancer.

Breakage and reunion A method of genetic recombination in which two DNA duplex molecules are broken at corresponding points followed by rejoining crosswise. This forms a heteroduplex at the site if joining.

Breast – milk jaundice a type of retention jaundice that arises due to defective hepatic conjugation or bilirubin. It occurs in some infants due to the presence of pregnane -3β-20α-doil, an inhibitor of glucuronyl transferase present in breast milk. Hypothyroidism delays the maturation of the enzyme. Drugs such as novobiocin have been reported to inhibit enzyme activity especially in the neonatal state when the activity of the enzyme is decreased.

Breed 1. A subspecific group of domestic livestock with definable and identifiable external characteristics that enable it to be separate from other similarly defined groups within the same species 2. A group of domestic livestock for which geographical and/ or cultural separation from phenotypically similar groups has led to acceptance of its separate identity. (Source:FAO, 1999).

Breeding The process of sexual reproduction and production of offspring.

Brenner, Sydney A scientist who was awarded the Nobel Prize in Physiology or Medicine for year 2002, together with John Sulston and Robert Horvitz for seminal discoveries concerning the genetic regulation of apoptosis using the nematode Caenorhabditis elegans as an experimental model system. The scientists identified key genes regulating organ development and programmed cell death and demonstrated that corresponding genes exist in higher species, including man. The discoveries have shed new light on the pathogenesis of many diseases.

Brewer’s yeast Strains of yeast used for the production of beer. Saccharomyces cerevisiae is used most often.

Brewing The process of beer preparation. Barley grain is soaked in water and allowed to germinate in a process called malting. During malting, the enzymes present in the grain convert the seed starch to maltose, and then to glucose. The grain is then dried, crushed, and added to water at a specific temperature (steeping). Any starch that remains is converted to sugar. The resulting liquid termed wort, is the raw material to which yeast is added to convert sugar to alcohol. Hops (female flowers of Humulus lupulus) are added during this process to impart a characteristic flavor.