This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Techniques in molecular biology, Subject name: Biochemistry
Which of the following is the most common gene delivery system for 'In-vivo' gene therapy? 
Select and explain. 
A. Micro injection, B. Lipofection, C. Adeno viral vectors, D. Electroporation
C: Adeno viral vectors
Answer: C: Adeno viral vectors 
Explanation: Adenovirus in gene therapy: ds DNA virus Replication deficient Used in In Vivo approach gene therapy As vaccines, For cancer therapy Advantages: Remain as an episome (extrachromosomal DNA) So doesn't integrate into the genome. (no chance of inseional mutagenesis) The maximum size of the inse by the adenoviral vector is 36 kb.