Answer:
exposure to ultraviolet radiation is a correct answer.
Explanation:
Ultraviolet light exposure results in the formation of pyrimidine dimers. Ultraviolet radiation damage the DNA by resulting in chemical changes.
Ultraviolet radiation is absorbed by the pyrimidine bases( cytosine and thymine in DNA) and result in the formation of covalent bonds between the succeeding bases.
The formation of the pyrimidine dimers results in the distortions of DNA helix and disrupt the base-pairing during the replication of DNA which results in a mutation.
Hypothalamus; pituitary gland
Hypothalamix-pituitary-adrenal axis is a complex set of direct influences and feedback interactions among the three organ components which are the hypothamus, pituitary gland and adrenal gland. These organ and their interactions forms the HPA axis that controls the reaction to stress and regulates many body processes,including digestion, immune system mood and emotions
