Question

Which of the following is a physical factor that induces mutation?
A) Acridines
B) $NHO_2$
C) UV-rays
D) Base analogue

Answer 1

Hint: Mutation is defined as the change in the DNA sequence. This change can be both by internal factors like during DNA copying or replication and by several other external factors like virus, ionising radiations, chemicals etc. The effects of mutation can be harmful, beneficial or even neutral.

Complete answer:
The agents which cause mutations are mutagens. These mutagens can cause permanent alteration in the sequence of the gene or DNA. These changes are heritable and can be transferred over generations. The mutagens are mainly chemicals or physical factors like ionising radiations like UV rays, X rays etc.

UV rays or the ultraviolet rays are the electromagnetic rays which enter the earth through the sun. The ozone layer filters the UV rays but still some amount of it enters the earth surface. These rays penetrate inside the cells of the organism and can lead to mutation or alteration in the genetic component.

Acridines- It is a basic compound which is similar to pyridine. It is a skin irritant and is used as a dye. These dyes cause chemical mutation but these mutations are reversible and are reverted spontaneously.

$NHO_2$- Nitrous acid is an unstable weak acid. It is a major pollutant which causes acid rain. It is a chemical mutagen which leads to deamination of the bases as a consequence of which alters the genetic makeup.

Base analogue- Base analogues are the chemicals that resemble the nitrogenous bases. They can easily be used as a substitute for the purine and pyrimidine bases so as to induce mutation at a certain point or sequence.

From the above discussion it is understood that only UV rays is the physical factor which induces mutation. The correct answer is C.

Note: UV rays cause mutation to the cytosine and thymine bases. It interacts with them and oxidises the bases. The mutations caused by UV rays causes cancer in which the cell divides uncontrollably as it does not get signal for apoptosis or programmed cell death.