This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
True statement about transgenic mice - 
Select and explain. 
A. Developed from DNA insertion into fertilized egg, B. Have same genome as parents except one or more genes, C. Homozygous are selected, D. All of these
D: All of these
Answer: D: All of these 
Explanation: Transgenic mice are generated by pronuclear injection of foreign DNA into fertilized mouse oocytes and subsequent transfer into the oviduct of pseudopregnant foster mothers.
This process of generating transgenic animal would alter germ cell lines and be passed on to offsprings. So, the transgenic animals have the same genome as parents except for few (1 or more) genes that have been integrated or inactivated.
This replacement of one gene in embryonic stem cell creates a heterozygous transgenic animals. The mating in 2 such animals will result in 25% homozygous offsprings. Careful breeding will establish a transgenic line in which all animals are homozygous for new genes.