What is one method to determine the genetic background of a transgenic mouse line?

• A. Phenotypic observation is sufficient for background genetics.
• B. Blood pressure measurement determines genotype.
• C. Visual inspection of fur color is enough.
• D. Genotyping using PCR to confirm specific transgene or allele presence.

Answer: (D)

Assessing the genetic background requires a direct look at the animal’s DNA. PCR-based genotyping provides a precise, scalable way to confirm exactly which transgene or allele is present and to test for strain-specific markers across the genome. This gives a clear picture of the background rather than relying on outward traits, which can be influenced by the transgene itself, environmental factors, or polygenic variation. In short, confirming the transgene and background alleles with PCR offers an objective, reliable readout of genetic background.