Lecture 3: Development of the Drosophila Body Plan I - Vocabulary

Vocabulary flashcards covering key terms related to AP/DV axis formation, maternal and zygotic genes, Drosophila embryology, and genetic screening concepts from Lecture 3.

Syncytial blastoderm

Stage in early Drosophila embryogenesis where nuclei divide rapidly without cell membranes, creating a multinucleate cytoplasm that will later form individual cells.

Cleavage

Rapid mitotic divisions after fertilization that lead to the syncytial blastoderm stage.

Gastrulation

Process by which the germ layers (mesoderm, endoderm, ectoderm) move inward; mesoderm and endoderm internalize while ectoderm remains on the outside.

Mesoderm

Germ layer that forms muscles and other tissues; located ventrally during gastrulation.

Endoderm

Germ layer that forms the gut; located at the poles during gastrulation.

Ectoderm

Outer germ layer forming the epidermis and nervous system.

Bicoid

Anterior maternal-effect gene product; a morphogen whose gradient patterns the anterior-posterior axis.

Nanos

Posterior maternal-effect gene; RNA-binding protein that helps establish posterior identity, partly by repressing translation of hunchback mRNA.

Hunchback

Zygotic transcription factor; its translation is repressed by Nanos to help pattern the AP axis.

Torso

Receptor tyrosine kinase activated at embryonic ends by the Trunk ligand to drive terminal gene expression.

Trunk

Ligand that activates the Torso receptor at the termini to pattern the ends.

Parasegment

Developmental units laid out in the embryo that give rise to individual segments; not visibly separated.

Gap genes

Zygotic genes that establish broad regions along the AP axis to provide positional information.

Pair-rule genes

Zygotic genes that define alternating segment boundaries and contribute to segmentation.

Segmentation genes

Zygotic genes that refine and coordinate segment formation along the AP axis.

Selector/Homeotic genes

Zygotic genes that determine segment identity; include homeotic genes that encode transcription factors.

Maternal effect gene

Gene whose offspring phenotype depends on the mother's genotype due to deposited maternal products in the egg.

Anterior group maternal genes

Maternal-effect genes specifying anterior identity in the embryo (e.g., bicoid-related factors).

Posterior group maternal genes

Maternal-effect genes specifying posterior identity (e.g., nanos).

Terminal group maternal genes

Maternal-effect genes specifying terminal structures via the Torso/Trunk pathway.

Morphogen

Substance that forms a concentration gradient and induces different cell fates at different threshold concentrations.

Morphogen gradient

Spatial distribution of a morphogen across a tissue guiding pattern formation.

Positional information

Concept that cells obtain identity based on their position within a gradient and differentiate accordingly.

Homologous genes

Genes with shared ancestry; have similar DNA sequences.

EMS mutagen

Ethyl methanesulfonate; chemical mutagen used to induce point mutations for forward genetic screens.

Balancer chromosome

Modified chromosome with markers and lethal mutations to maintain mutations in heterozygotes and suppress recombination.

Saturating screen

Genetic screen designed to identify as many genes as possible involved in a phenotype or process.