Question

Ultra-violet light causes

• A. Formation of pyrimidines dimers
  
• B. Sticky metaphases
• C. Photodynamic action
• D. Destruction of hydrogen bonds between complementary DNA strands

Answer 1

The correct option is A Formation of pyrimidines dimers

The Ultra-violet radiations are the potent mutagens as they are capable of distorting the structure of the DNA. The UV radiations cause the adjacent pyrimidines residues (thymine and cytosine) to form hydrogen bonds with each other rather than the corresponding purine residues. Generally, the thymine dimers are seen as immediate effects of the UV radiations. Due to this type of mutation, the errors in replication of DNA are frequent to observe. The breaking of hydrogen bonds between the two complementary DNA strands occurs due to increase in temperature. This is not considered as a mutation because when normal conditions arrive the hydrogen bonds can be formed again.

Hence, the correct answer is 'Formation of pyrimidines dimers'.