Question

Briefly explain the following terms.
(i) Genes
(ii) Cytokinesis in plant cells
(iii) Guttation
(iv) Diabetes insipidus
(v) Disinfectants

Answer 1

(i) Genes : Genes are units of heredity that determine particular traits. These are the small segments of DNA. They encode for certain proteins which are responsible for characters. (e.g., colour of hair, blood group, colour of eye etc.)

(ii) Cytokinesis in plant cells : Cells in multicellular plants do not have centrioles. The division of cytoplasm occurs by the formation of a new cell wall in the equatorial region at the end of anaphase. In telophase, new cellulose particles are gradually deposited in the equatorial zone. The particles extend on either side, from the centre towards the periphery (centrifugal) until it completely divides the cell. These particles fuse together to form a delicate plate membrane.

(iii) Guttation : The loss of water in the form of water droplets along the margins of leaves through hydathodes. It takes place due to increased hydrostatic pressure that builds up within the cells. The wall pressure that develops in fully turgid parenchymatous cells force the water out.

(iv) Diapedes insipidus : The condition occurs due to lesser secretion of vasopressin (Anti-diuretic hormone) from the posterior lobe of pituitary gland. The disease is characterized by excretion of large amounts of urine and subsequent dehydration and thirst. No sugar or albumin is present in the urine. A person with severe diabetes insipidus may die due to dehydration if deprived of water for few days.

(v) Disinfectants : These are powerful chemical substances used for destroying microbes in spots, places for sterilizing operation theatres and surgical instruments. They are not applied on the body due to their strong corrosive nature eg. Cresol, Phenol, Lysol, DDT etc.