Development of the Drosophila Egg and Body Plan - Vocabulary

Vocabulary flashcards covering key terms and definitions related to early Drosophila embryonic patterning and axis formation as described in the lecture notes.

Maternal genes

Genes expressed in the mother whose products (mRNAs/proteins) deposit into the egg to establish early anterior-posterior and terminal cues before zygotic transcription begins.

Zygotic genes

Genes activated after fertilization that pattern the embryo; include gap, pair-rule, segmentation, and selector/homeotic genes.

Anterior-Posterior (A/P) polarity

Axis polarity in the embryo established by maternal factors and follicle-cell signals, guiding head-to-tail organization.

Gurken

Oocyte-derived signal that activates the Torpedo receptor in surrounding follicle cells, helping orient microtubules and establish polarity.

Torpedo

Receptor tyrosine kinase on follicle cells activated by Gurken to specify posterior follicle cells and trigger cytoskeletal rearrangements.

E-cadherin

Cell-adhesion molecule expressed in the oocyte and posterior follicle cells, contributing to proper oocyte positioning and patterning signals.

Bicoid (bicoid)

Maternal mRNA/protein gradient that specifies anterior identity and activates targets like hunchback to pattern the AP axis.

Hunchback

Zygotic transcription factor activated by Bicoid; defines anterior regions and activates other gap genes.

Gap genes

Class of zygotic transcription factors that define broad regions along the AP axis (e.g., hunchback, giant, Krüppel, knirps).

Krüppel

Gap gene activated by Bicoid and intermediate Hunchback; repressed by high Hunchback levels, helping refine boundaries.

Giant

Gap gene contributing to AP patterning; interacts with other gap genes to shape domains.

Knirps

Gap gene contributing to AP domain formation; part of the gap gene network.

Pair-rule genes

Genes expressed in alternating parasegments to subdivide the embryo into repeating units; examples include even-skipped (eve).

Even-skipped (eve)

A key pair-rule gene expressed in seven stripes; stripe formation controlled by input from gap genes and maternal factors.

Parasegments

Developmental units that give rise to segments; defined by gene activity and offset from actual segments by about half a segment.

Dpp (Decapentaplegic)

Dorsal-most morphogen (TGF-β family) that patterns the dorsal region; expressed dorsally and modulated by other factors.

Sog (Short gastrulation)

Binds Dpp to prevent receptor interaction, helping to focus Dpp activity dorsally and shape the DV gradient.

Spätzle

Ligand produced in ventral follicle cells that activates Toll signaling to establish ventral patterning.

Toll

Cell-surface receptor activated by Spätzle; initiates the signaling cascade leading to Dorsal nuclear localization.

Dorsal

Transcription factor whose ventral nuclear localization defines DV patterning; activates ventral genes (e.g., twist, snail) and represses dorsal fate (e.g., dpp) ventrally.

Cactus

Inhibitor of Dorsal that is degraded upon Toll signaling, allowing Dorsal to enter nuclei.

Twist

Ventrolateral gene activated by high Dorsal levels; essential for mesoderm formation.

Snail

Ventral gene activated by high Dorsal; collaborates with Twist in mesoderm development.

Rhomboid

Gene activated by lower Dorsal levels; contributes to DV patterning by affecting signaling pathways.

LacZ reporter

A reporter gene used to monitor gene expression (e.g., hunchback) by blue coloration when expressed.

Dorsal-Ventral axis

DV axis patterned by Toll/Dorsal signaling, Spätzle ligand, Dpp/Sog dynamics, and downstream targets.

Germline stem cells

Stem cells in the ovary that divide to produce cystoblasts, which form 16-cell cysts; one cell becomes the oocyte while others become nurse cells.

Oocyte

The developing egg cell that captures maternal determinants and, after fertilization, contributes to embryonic axes.

Nurse cells

Egg-supporting germline cells that donate RNA/protein to the oocyte during oogenesis.

Follicle cells

Somatic cells surrounding the germline cysts; provide patterning signals (Gurken/Torpedo, Spätzle) to the oocyte and contribute to eggshell formation.

Trunk

Terminal signaling molecule from follicle cells that patterns the terminal structures of the embryo.