What is the best age to genotype a mouse in order not to disturb the litter?

• A. Right after birth
• B. In the first two weeks of life
• C. Around weaning time
• D. When it reaches sexual maturity

Answer: (C)

Genotyping should be timed to minimize disruption of the dam–pup bond and nursing. The neonatal period is when pups are most dependent on the dam, and handling them early can interfere with nursing, increase maternal stress or aggression, and even raise the risk of pup loss. Around the time of weaning, pups are older, more robust, and you’re already separating them from the dam for the weaning process. Performing genotyping at this stage lets you collect DNA samples during an already planned routine handling event, reducing additional disturbance to the litter. It also minimizes stress on the dam and pups because you’re not introducing a separate, early-handling procedure. Delaying to after weaning or doing it right after birth would either increase risk to the litter or unnecessarily delay colony management, while waiting until sexual maturity adds unnecessary handling and logistical complexity.