Q.89 Zygotic genes required for the formation of a group of adjacent segment in the developing
Drosophila embryo is called
(A) Maternal gene (B) Pair rule gene (C) Homeotic gene (D) Gap gene
Zygotic pair-rule genes in Drosophila define adjacent segment groups by expressing in seven stripes across the embryo, establishing parasegment boundaries.
This segmentation cascade step follows gap genes and precedes segment polarity genes.
Correct Answer
(B) Pair rule gene
Option Analysis
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(A) Maternal gene: Maternal genes (e.g., bicoid, nanos) are deposited by the mother in the egg, creating anterior-posterior gradients that activate zygotic genes; they do not form segment groups themselves.
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(B) Pair rule gene: Zygotic pair-rule genes (e.g., even-skipped, fushi tarazu) activate in seven alternating stripes, subdividing gap gene domains into adjacent segment primordia and setting parasegment boundaries.
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(C) Homeotic gene: Homeotic genes (Hox cluster like Antennapedia) specify segment identity (e.g., leg vs. antenna) after segmentation is complete; they do not form segments.
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(D) Gap gene: Gap genes (e.g., hunchback, Krüppel) divide the embryo into broad regions, deleting large gap-like sections in mutants; finer adjacent segment formation requires pair-rule genes.
Drosophila Segmentation Hierarchy
Maternal gradients → gap genes (broad domains) → pair-rule genes (7 stripes → 14 parasegments) → segment polarity genes (intra-segment polarity) → homeotic genes (identity). Mutations in pair-rule genes delete every other segment pair.
Drosophila Zygotic Pair Rule Genes: Segment Formation Key
Drosophila zygotic pair rule genes drive formation of adjacent segments in the developing embryo. These zygotic segmentation genes express in periodic stripes post-gap gene activation, creating the 14-parasegment blueprint essential for body plan.
Gene Classes Compared
| Gene Type | Zygotic? | Segment Role | Mutant Effect |
|---|---|---|---|
| Pair-rule | Yes | Adjacent segment groups via 7 stripes | Paired segment deletions |
| Maternal | No | A-P gradients | Polarity defects |
| Homeotic | Yes | Identity post-segmentation | Transformations |
| Gap | Yes | Broad domains | Large gaps |
Drosophila zygotic pair rule genes like eve and ftz integrate gap inputs for precise patterning, foundational for GATE Life Sciences developmental biology.
GATE Prep Insights
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Hierarchy: Maternal > gap > pair-rule > segment polarity > homeotic.
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Key examples: Primary (ftz, eve), secondary (hairy, runt).
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Test focus: Pair-rule defines “group of adjacent segments”.
1 Comment
Ankita Pareek
May 7, 2026Drosophila zygotic pair rule gene
Option D is correct