Final answer:
The Antennapedia mutation in Drosophila represents a dominant mutant allele that overrides even the wild-type phenotype by altering the distribution of the gene product, causing unusual development such as legs on head. Eye color in Drosophila is also an example of dominance, where red is dominant over white and is linked to the X chromosome.
Step-by-step explanation:
Based on how it is written, the dominant mutant allele in Drosophila is exemplified by the Antennapedia mutation. This particular mutant allele is dominant over other phenotypes, including the wild type, because of its ability to interfere with the genetic message. In a heterozygote, with only one copy of the wild-type allele, the mutant phenotype can still be expressed. The Antennapedia mutation is particularly interesting because it causes the gene product to have an expanded distribution within the organism, resulting in the development of legs on the head where antennae would normally be found.
Another example in fruit flies is the eye color gene located on the X chromosome. Red eye color, which is wild-type, is coded by XW and is dominant to white eye color, coded by Xw. This is important in understanding dominance, as Drosophila males are hemizygous and have only one allele for any X-linked characteristic, making them XWY or XwY.
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