Assertion : Senescence is the time when age associated defects are manifested. Reason : Certain genes may be undergoing sequential switching on and off during one's life.

Step-by-step solution

Process of ageing is called senescence. Ageing, is cumulative changes in an organism, organ, tissue, or cell leading to a decrease in functional capacity. In humans, aging is associated with degenerative changes in the skin, bones, heart, blood vessels, lungs, nerves, and other organs and tissues. It is genetically controlled programme regulated by regulatory genes. This view is suggested by the great range of lifespans among different animal speciesfrom a few days in the fruit fly to more than 100 years in some to