Biology Test 273

Statins are products of fermentation activity of yeast Monascus purpureus which resemble mevalovate and are competitive inhibitors of b hydroxy–b–methylglutaryl or HMG CoA reductase. This inhibits cholesterol synthesis. Statins are, therefore, used in lowering blood cholesterol, e.g., lovastatin, pravastatin, simvastatin.

Plasmid is a small circular double stranded DNA molecule present in the cytoplasm of the bacterial cell. It can replicate independently of bacterial chromosome. Due to this characteristic of plasmid, it is used as the vector (vectors are for the transferring of a piece of DNA to target gene) in gene cloning.

DNA restriction endonuclease are important, which cut double-stranded DNA molecules only at sites characterized by a specific nucleotide sequence. Restriction enzymes are isolated from bacterial cells and are tools for molecular biologists.

Meloidogyne incognita is a nematode which infects the roots of the tobacco plants and causes a great reduction in the yield.

Golden rice is a transgenic variety of rice (Oryza sativa) which contains good quantities of b-carotene (provitamin A - inactive state of vitamin A). b-carotene is a principal source of vitamin A. Since the grains of this rice is yellow in colour due to b-carotene, it is commonly called golden rice.

The small animals have smaller surface area to body volume ratio. They have higher metabolic rates than larger animals. Therefore, it is much easier for small animals to move uphill than large animals.

Biological or biotic community is an assemblage of populations of different species of plants, animals, bacteria and fungi which live in a particular area and interact with one another through competition, predation, mutualism, etc. Each biotic community has a specific composition and structure, e.g., pond community.