Final answer:
To determine if white spots in gerbils are due to a dominant or recessive allele, perform monohybrid crosses and analyze the F1 and F2 generation using a Punnett square. If F1 offspring all exhibit the trait, it's likely dominant. A 3:1 phenotypic ratio in the F2 generation would confirm this if the trait is dominant, or suggest it's recessive if the ratio differs.
Step-by-step explanation:
To determine if white spots in Mongolian gerbils are due to a recessive or dominant allele, you can perform monohybrid crosses using a Punnett square. Cross gerbils with white spots (assuming they are homozygous for the trait) with those that have solid coats (again, assumed to be homozygous) to observe the F1 generation. If all the offspring have white spots, the trait is likely dominant. However, if none do, white spotting is probably recessive. To confirm, you can cross F1 gerbils to observe the F2 phenotypic ratio; a 3:1 ratio of spotted to solid coat would support simple dominance.
For instance, assuming white spots are due to a recessive allele, a cross between homozygous recessive gerbils (ss) and homozygous dominant (SS) for solid color should yield all heterozygous offspring (Ss) that have solid coats, if solid is dominant. If all F1 offspring exhibit white spots, this would suggest the white spot allele is dominant. A subsequent cross of F1 gerbils (Ss) should give a 3:1 phenotypic ratio of solid to spotted if the spotted trait is dominant, or vice versa if recessive.
This methodology is analogous to Mendel's monohybrid crosses where a single trait is being studied. Simple dominance can also be observed in pedigrees, which do not show the trait skipping generations, while in case of recessive traits, it may skip a generation. However, two white-spotted parents should never produce a solid-coat offspring if the trait is due to a dominant allele.