Final answer:
The death of the mouse in the given scenario is most likely caused by a recessive lethal allele, as both mice were homozygous for the same allele and raised under the same conditions. Dominant lethal alleles are usually not passed on through generations, as they tend to be lethal in heterozygotes as well.
Step-by-step explanation:
The type of allele likely responsible for the death of the mouse is a recessive lethal allele. Since both mice were homozygous for the same allele and raised under identical conditions, the death can most reasonably be attributed to a genetic factor. In the case of a recessive lethal allele, two copies of this allele can result in death, while a single copy in a heterozygote may not be lethal. For genes essential for survival, a nonfunctional mutant allele that is recessive could be tolerated in individuals who are heterozygous for one wild-type allele and one mutant allele. However, homozygotes with two copies of the nonfunctional allele may fail to survive.
An example of a dominant lethal allele is Huntington's disease in humans, where heterozygotes (Hh) will develop the disease, but because the onset is often after reproductive age, the allele can still be passed on to offspring. In contrast, a recessive lethal allele, when present in both copies, leads to lethality possibly before birth, as seen in some animal models. Therefore, in this scenario with both mice being homozygous, it is more likely that the lethal allele is recessive rather than dominant, as dominant lethal alleles are rare and typically not seen in multiple generations.