This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
True statement about transgenic mice is 
Select and explain. 
A. Developed from DNA inseion into feilized egg, B. Have same genome as parents except one or more genes, C. Identical genome to parent mice, D. Produced by breeding over several generations
A: Developed from DNA inseion into feilized egg
Answer: A: Developed from DNA inseion into feilized egg 
Explanation: In 1974 Rudolf Jaenisch created the first genetically modified animal by inseing a DNA virus into an early-stage mouse embryo and showing that the inseed genes were present in every cell.