Final answer:
While we can't specify the exact genotype of an alien with four-fingered hands without more information, we can infer from human genetic principles that the majority of people having five fingers is due to the rarity of the polydactyl allele.
Step-by-step explanation:
The question of what genotype would produce an alien with four-fingered hands cannot be definitively answered without more information about the genetic makeup and inheritance patterns of this hypothetical alien species. However, we can draw on knowledge of genetic principles from Earth organisms to provide some insight.
In humans, the gene associated with polydactyly (having six fingers) is a dominant trait. However, the majority of people have five fingers because the polydactyl allele is very rare in the human population. For a species with typically four fingers,
It would similarly depend on the dominance and prevalence of the alleles governing the number of fingers. If an allele for four fingers is dominant, and the population generally exhibits this trait, then most individuals would have the genotype with at least one dominant allele for four fingers
Should the population exhibit a wide variety of alleles for finger number, counting the possible genotypes would involve considering all the possible combinations of these allelen .Additionally, changes in chromosome number, such as forming offspring with a tetraploid set of chromosomes.
Could also lead to reproductive isolation from the ancestral species. Such changes might hypothetically be associated with different physical traits in a new species, including finger number.