A Drosophila researcher has recently isolated a number of mutant fruit flies. Th

Question

A Drosophila researcher has recently isolated a number of mutant fruit flies. The phenotype of each mutant is described below (i–iv). For each mutant, describe the type of gene (maternal-effect gene, gap gene, segment-polarity gene, or homeotic gene) that was most likely the cause of the altered phenotype. Briefly explain your answer

(i) Homozygous mutant females appear phenotypically normal but produce larvae that have two posterior ends.
(ii) The flies contain four wings rather than two.
(iii) The wings are oriented backward.
(iv) The flies are missing two pairs of legs due to a shortened thoracic region

Explanation / Answer

Homeotic genes are genes that determine which parts of the body form what body parts. They are involved in determining where, when, and how body segments develop in flies. Alterations in these genes cause changes in patterns of body parts, sometimes causing dramatic effects such as legs growing in place of antennae or an extra set of wings. So (ii) would most likely be a homeotic gene mutation. From Wikipedia: In maternal-effect gene, if a mutation is maternal effect recessive, then a female homozygous for the mutation may appear phenotypically normal, however her offspring will show the mutant phenotype, even if they are heterozygous for the mutation. So (i) would be a maternal-effect mutation. A gap gene is a type of gene involved in the development of the segmented embryos of some arthropods. Gap genes are defined by the effect of a mutation in that gene, which causes the loss of contiguous body segments. Therefore, (iv) is most likely due to gap gene mutation. I couldn't find much for segment-polarity, other than it's function is to define the anterior and posterior polarities within each embryonic parasegment. It contains the gene 'engrailed' which is a transcription factor involved in multicellular development. So my guess would be that (iii) is caused by a segment-polarity mutation.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.