Developmental genetics definitions

Maternal Effect

The influence of the mother’s genotype on the offspring’s phenotype through egg cytoplasm contributions.

Actinomycin D

A transcription inhibitor that blocks RNA synthesis, used to study maternal mRNA function.

Dextral Coiling

A right-handed spiral pattern in snail shells determined by the maternal genotype.

Sinistral Coiling

A left-handed shell coiling resulting from maternal mutation in the D gene.

Cytoplasmic Determinants

Molecules like mRNA and proteins in the egg that specify embryonic axes.

Three-Parent Baby

A technique involving nuclear transfer to bypass defective mitochondrial DNA in the egg.

Paternal Rescue Effect

Phenomenon where paternally inherited alleles compensate for defective maternal alleles.

Maternal RNA Localization

The process of transporting and anchoring mRNA to specific regions of the egg.

Egg Polarity

The asymmetric distribution of cytoplasmic determinants setting up the anterior-posterior axis.

Nanos Gene

A maternal-effect gene specifying posterior body structures in Drosophila.

Bicoid Gene

Encodes a morphogen forming a gradient to establish anterior-posterior axis in Drosophila.

Hunchback Gene

A zygotic gap gene activated by bicoid that specifies anterior segmentation.

Pole Cells

Precursors of germ cells formed at the posterior end of Drosophila embryos.

Swallow Gene

Assists in localizing bicoid mRNA to the anterior of the egg.

Exuperantia Gene

Works with swallow to anchor bicoid mRNA during oogenesis.

Anterior-Posterior Axis

Developmental axis defined by gradients like bicoid and nanos proteins.

Gap Genes

Regulate large regions of the embryo, such as hunchback.

Cytoplasmic Gradient

Distribution of proteins like bicoid that directs cell fate.

Fate Map

Diagram showing how embryonic regions correspond to adult structures.

Blastoderm

A single layer of cells in early embryogenesis where patterning begins.

Gurken Gene

Encodes a signaling molecule that determines dorsal follicle cell fate.

Torpedo Gene

Receptor for gurken involved in dorsal-ventral polarity establishment.

Ventralized Egg

An egg phenotype where ventral structures replace dorsal ones due to polarity gene mutations.

Dorsalized Egg

An egg phenotype lacking ventral structures, caused by gurken overexpression.

Complementation Test

A method to determine if two mutations affect the same gene.

Toll Pathway

A signaling cascade activating Dorsal protein in ventral cells.

Pole Cell Formation

Creation of germ cell precursors in the posterior pole of the embryo.

Dorsal Gradient

A nuclear gradient of Dorsal protein that activates ventral genes.

Zygotic Genes

Genes expressed in the embryo post-fertilization to define cell fates.

Cytoskeletal Anchoring

The role of microtubules in localizing maternal mRNAs like gurken.

Dorsal Protein

A transcription factor forming a nuclear gradient to specify ventral cell fates.

Cactus Protein

Sequesters Dorsal protein in the cytoplasm; degraded upon Toll activation.

Spätzle Protein

Ligand for the Toll receptor, activating ventralization pathways.

Pipe Gene

Specifies ventral follicle cells by modifying extracellular proteins.

Zinc Finger Protein

DNA-binding proteins like hunchback involved in transcription regulation.

Ventralized Embryo

An embryo where ventral structures expand due to dorsal group mutations.

Dorsalized Embryo

An embryo where dorsal structures expand due to ventralization loss.

Toll Receptor

Mediates signal transduction in Drosophila polarity pathways.

Gene Hierarchy

Sequential activation of genes in developmental pathways.

NF-κB

Human homolog of Dorsal protein, involved in immune responses.

Homeosis

Transformation of one body part into another due to homeotic gene mutations.

Atavism

Reappearance of ancestral traits, such as four wings in Drosophila mutants.

Hox Genes

Genes regulating segmental identity in body plans.

Homeobox

Conserved DNA sequence in Hox genes that encodes transcription factors.

Knockout Mouse

A model organism with specific gene functions inactivated.

Bithorax Complex

Hox genes regulating thoracic and abdominal segment identity.

Antennapedia Mutation

Mutation causing antennae-to-leg transformations.

Segment Polarity Genes

Define polarity within segments, like wingless.

Evolutionary Conservation

Similarity of Hox gene function across species.

Morphogenetic Field

Region where cells receive positional information for patterning.

Sonic Hedgehog (Shh)

A morphogen regulating anterior-posterior limb patterning.

Apical Ectodermal Ridge (AER)

Structure promoting limb outgrowth along the proximo-distal axis.

Proximo-Distal Axis

Limb axis running from the body core to the limb tips.

Retinoic Acid

A signaling molecule essential for limb and organ development.

Lmx1b Gene

Specifies dorsal limb identity; mutations cause Nail-Patella syndrome.

Zone of Polarizing Activity (ZPA)

Limb bud region secreting Shh for anterior-posterior patterning.

Growth Factors

Molecules like FGFs driving cell proliferation in limb development.

Humerus Formation

Dependent on AER signaling gradients.

Pluripotency

Ability of stem cells to differentiate into multiple tissues.

Digit Apoptosis

Cell death shaping interdigital spaces during limb formation.

Dosage Compensation

Mechanism equalizing X-linked gene expression between sexes.

SRY Gene

A Y chromosome gene initiating male sex determination.

Sex-lethal (Sxl) Gene

Regulates female development in Drosophila.

Barr Body

Inactivated X chromosome in female cells, ensuring dosage compensation.

Haploid-Diploid System

Males develop from unfertilized eggs, females from fertilized eggs.

Turner Syndrome

Disorder in females with only one X chromosome (XO).

Klinefelter Syndrome

Disorder in males with an extra X chromosome (XXY).

Androgen Insensitivity Syndrome

XY individuals with female characteristics due to androgen receptor defects.

Pseudohermaphroditism

Chromosomal and phenotypic sex mismatch.

Gonadal Ridge

Embryonic precursor of testes or ovaries.