Final answer:
The correct answer is a) Dominant. In genetics, a dominant allele masks the presence of a recessive allele in the phenotype of an individual. An example of a dominant mutation is the Antennapedia mutation in Drosophila.
Step-by-step explanation:
If a mutation is dominant-acting, whichever allele of the gene is dominant will override any other allele of that gene in the cell. The correct answer to the fill-in-the-blank question is a) Dominant.
In genetics, dominance describes the relationship between alleles where the dominant allele masks the presence of a recessive allele in the phenotype of an individual. This means that an organism with at least one dominant allele will display the characteristics associated with that dominant allele. A simple example is blood type: an individual with one allele for blood type A and one for blood type O will show the blood type A phenotype because the A allele is dominant.
Mutations can be dominant for various reasons, such as by enhancing the function of a wild-type gene product or changing its distribution in the body. An example is the Antennapedia mutation in Drosophila, where the mutant allele causes legs to develop on the head of the fly.