NEET BIOLOGY

Detailed explanation-1: -Mutations result either from errors in DNA replication or from the damaging effects of mutagens, such as chemicals and radiation, which react with DNA and change the structures of individual nucleotides. All cells possess DNA-repair enzymes that attempt to minimize the number of mutations that occur (Section 14.2).

Detailed explanation-2: -Mutations can result from errors in DNA replication during cell division, exposure to mutagens or a viral infection. Germline mutations (that occur in eggs and sperm) can be passed on to offspring, while somatic mutations (that occur in body cells) are not passed on.

Detailed explanation-3: -When ionising radiation acts upon gonads or germ cells, it may cause damage to the genetic material (mutations) which can lead to genetically induced diseases (hereditary defects). An association between radiation exposure and the occurrence of hereditary damage has not been observed in humans to date.

Detailed explanation-4: -Mutations result either from accidents during the normal chemical transactions of DNA, often during replication, or from exposure to high-energy electromagnetic radiation (e.g., ultraviolet light or X-rays) or particle radiation or to highly reactive chemicals in the environment.

Detailed explanation-5: -Random, unpredictable DNA “mistakes” account for nearly two-thirds of the mutations in cancers. These mutations occur as a result of DNA copying errors made when normal cells divide. What causes such random DNA copying errors? Human cells are constantly regenerating.