Biology Test 272

The expression of the genetic material occurs normally through the production of proteins. This involves two consecutive steps. These are transcription and translation. The DNA codes for the production of messenger RNA (mRNA) during transcription. Messenger RNA carries coded information to ribosomes. The ribosomes read this information and use it for protein synthesis. This process is called translation. F.H.C. Crick described this unidirectional flow of information in 1958 as the ‘central dogma of molecular biology’

The condition for origin of life, partial isolation, has been attained within aggregates of artificially formed prebiotic molecules. These aggregates are called protobionts which can separate combinations of molecules from the surroundings. They maintain an internal environment but are unable to reproduce. Two important protobionts are coacervates and microspheres.

Chemical evolution has two meanings and uses. The first refers to the theories of evolution of the chemical elements in the universe through nucleosynthesis. The second use of chemical evolution or chemosynthesis is as a hypothesis to explain how life might possibly have developed or evolved from non-life.

Elephantiasis is caused by the parasitic filarial worm, Wuchereria bancrofti which is transmitted from an infected person to a healthy person via the bite of mosquito (especially Culex). It is characterised by gross enlargement of the skin and underlying connective tissues caused by lymphatic obstruction of lymph vessels by these worms which prevent drainage of lymph from the surrounding tissues. The parts commonly affected are legs, feet, thighs but scrotum, breasts and vulva may also be involved.

Cholera is caused by bacterium Vibrio cholerae, tetanus is caused by bacterium Clostridium tetani, typhoid is caused by bacterium Salmonella typhi, small pox is caused by Variola virus, mumps is caused by Paramyxo virus, Herpes is caused by Herpes simplex virus and influenza is caused by Orthomyxovirus.

In interspecific hybridisation, a species is mated with a different related species of the same genus. Interspecific hybrids are generally difficult to produce, but they are important in plant breeding, particularly in breeding for disease resistance. This is also called intrageneric hybridisation.

Mackerel is a marine fish, rich in omega-3-fatty acids. Mystus, Mangur and Mrigala are freshwater fishes.

Outbreeding is the breeding of unrelated animals, which may be between individuals of the same breed (but having no common ancestors), or between different breeds (cross breeding) or different species (inter specific hybridisation). Outbreeding is an important strategy of animal husbandry as it helps to overcome inbreeding depression.

Cheese is a protein rich nutritive preparation obtained after fermentation and curdling of milk. Cheese contains proteins (20-35%), fats (20-30%), minerals, vitamins and water. Milk is first curdled (soured) with the help of a lactic acid bacterium. Curd is gently heated to separate cheese from liquid called whey. Curd is placed in cloth-lined porous containers for draining out whey. The left out solidified material is called cottage cheese. For preservation and ripening, blocks of cottage cheese are salted and placed in brine solution. Salt solution is drained out. Cheese blocks are wiped and placed in sterilised rooms for ripening with the help of microorganisms.