This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Molecular Biology Techniques, Subject name: Biochemistry
Purpose of gene therapy: 
Select and explain. 
A. Replacement of abnormal gene by normal gene, B. Replacement of normal gene by abnormal gene, C. Knock out of abnormal gene, D. Introduction of viral gene
A: Replacement of abnormal gene by normal gene
Answer: A: Replacement of abnormal gene by normal gene 
Explanation: Ans. A. Replacement of abnormal gene by normal geneNovel area of therapeuticsIntracellular delivery of genes to generate a therapeutic effect by correcting an existing abnormalityDivided into1. Somatic cell gene therapy: Gene is introduced into somatic cells.2. Germ cell gene therapy (Transgenic animal)