Select the correct options to fill up the blanks.
(i) ______enzymes is crucial for the immune system to function and its absence is caused by the deletion of a gene.
(ii) Insulin consists of _____and _____that are linked together by ____.
(iii) Transgenic mice are being used to test the safety of the _____.
(iv)______involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA.