Fertilization, cleavage, gastrulation, germ layers, morphogens, body-axis formation, evo-devo.
Developmental Biology
Fertilization
Fusion of haploid gametes to form diploid zygote. Sperm-egg recognition (ZP3), acrosome reaction, membrane fusion, cortical reaction…
Cleavage divisions
Rapid early mitotic divisions without growth, partitioning zygote cytoplasm into blastomeres. Holoblastic (mouse, sea urchin) vs…
Gastrulation
Large-scale morphogenetic movements converting blastula to gastrula with three germ layers. Wolpert: 'it is not birth, marriage, or death,…
Germ layer
Three primary embryonic tissue layers: ectoderm (skin, nervous system), mesoderm (muscle, bone, blood, kidney, heart), endoderm (gut,…
Morphogen
Secreted signalling molecule forming concentration gradients that specify positional information. Classical: Bicoid, BMP, Shh, Wnt,…
Hox gene
Homeobox-containing transcription factors specifying anterior-posterior body-plan identity. Collinear arrangement in chromosomal clusters;…
Neurulation
Formation of neural tube from ectoderm. Notochord-induced neural plate folds along midline → neural groove → neural tube closure. Defects:…
Spemann organizer
Dorsal lip of amphibian blastopore that induces secondary body axis when transplanted (Spemann-Mangold 1924). Secretes BMP antagonists…
Embryonic induction
Spemann: signals from one tissue redirecting fate of neighbouring tissue (organiser grafts induce secondary body axis). Mediated by Wnt,…
Body-plan segmentation
Nüsslein-Volhard & Wieschaus 1980 Drosophila screen: maternal → gap → pair-rule → segment-polarity gene cascade establishes segments. Nobel…
Turing reaction-diffusion pattern formation
Turing 1952: instability of homogeneous steady state in two-morphogen reaction-diffusion system u_t = D_u ∇²u + f(u,v), v_t = D_v ∇²v +…
Wolpert positional information (French flag)
Wolpert 1969: cells read morphogen concentration C(x) (e.g. Bicoid in Drosophila) and adopt fates by threshold partitioning of C.…
Morphogen gradient (Wolpert French-flag)
Wolpert 1969 French-flag model: positional information from morphogen-concentration gradient; threshold-readout into discrete cell fates;…
Hox genes (colinearity, Lewis 1978)
Lewis 1978 Drosophila bithorax (Nobel 1995) + Krumlauf 1990s vertebrate Hox: spatial-temporal colinearity 3'->5' = anterior->posterior;…
Gastrulation + germ-layer formation
Vogt 1929 fate-mapping + Spemann-Mangold 1924 organizer: blastula gastrulates via primitive-streak (amniotes) / blastopore (anamniotes); 3…
Limb bud (AER + ZPA, Shh + FGF)
Saunders 1948 AER + ZPA: apical-ectodermal-ridge FGF8 maintains progress-zone proximodistal; zone-of-polarizing-activity Shh…
Notch-Delta lateral inhibition
Collier-Monk-Maini 1996 mathematical lateral-inhibition: Notch-receptor up-regulates by adjacent Delta-ligand binding; bistable feedback…
Polycomb-Trithorax cell memory
Lewis 1978 Pc + Kennison-Tamkun 1988 trxG: Polycomb (PRC1/2 H3K27me3 silencing) + Trithorax (MLL H3K4me3 activating) maintain Hox-state…
Heidelberg screen (Nüsslein-Volhard 1980)
C Nüsslein-Volhard-E Wieschaus 1980 (Nobel 1995) Drosophila zygotic-screen 5000-mutants; modern modern bicoid + gap + pair-rule +…
DV (Anderson-Roth 1987)
K Anderson-S Roth 1987 dorsal-NF-κB-Toll DV-axis; modern modern Toll-Spätzle + immune-link Lemaitre 1996 (Nobel Hoffmann 2011).
Hox (McGinnis-Gehring 1984)
W McGinnis-W Gehring 1984 homeobox; modern modern foundational text + co-linearity + 1980s Hox-evolution Carroll 2005 evo-devo.
Turing pattern (1952)
A Turing 1952 reaction-diffusion morphogen; modern modern foundational text + 2024 modern verified zebrafish-pigment + skin-pattern fish.
Notch (Artavanis 1985)
S Artavanis-Tsakonas 1985 Notch-cloning; modern modern foundational + lateral-inhibition + γ-secretase-modulator + cancer + nicastrin.
PCP (Adler 1992)
P Adler 1992 + Mlodzik 1995 planar-cell-polarity Fz/Vang; modern modern foundational + ciliogenesis + neural-tube-defects link 2024.