This kind of modeling is known as (D) simulation. A computer program is used to simulate an environment, in this case, the zoo. Instead of having to do an actual experiment which harms real animals, a simulation is done to cut costs and avoid using live samples.
Answer:
The trait is inherited in the homozygous recessive pattern
Possible mating is between two heterozygous individuals
Explanation:
One possible explanation for this is that the trait for this brown mice has to inherited in the homozygous recessive condition. It is possible for this trait to skip two generations and then reappear if it has to be inherited in the homozygous recessive condition.
Another explanation to complement the first is that for this trait to reappear, there was mating between two heterozygous individuals (with one allele being domiant and the other being recessive). It is possible that all matings within the two skipped generations was between an heterozygous and a homozygous dominant or between two homozygous dominant individuals which will not produce the brown mice..