Set of processes that mold the internal and external configuration of an embryo
Pattern formation involves spatial and temporal distribution or organization of differentiated cells
Examples include limb formation, establishment of fundamental axes, branching of ducts within glands, and formation of loops and whorls of fingers (fingerprints)
Six processes involved in morphogenesis: cell proliferation, cell migration, cell aggregation/cell adhesion, secretion of extracellular substances, change in cell shape, localized cell death/apoptosis
Fields of Embryology include Descriptive Embryology, Comparative Embryology, Experimental Embryology, Chemical Embryology, Reproductive Biology, and Teratology
Descriptive Embryology accounts for the processes transforming a single cell zygote into a multicellular organism, providing step-by-step descriptions and techniques like serial section and three-dimensional wax plate reconstructions
Comparative Embryology analyzes similarities and differences in the development of different vertebrate groups, providing insights into evolutionary relationships and taxonomic classifications
Experimental Embryology involves testing hypotheses and manipulating embryos through experiments like tissue and organ transplants, with pioneers like Wilhelm Roux
Reproductive Biology focuses on problems of conception and contraception, emphasizing normal gametogenesis, fertilization, endocrinology of reproduction, and early embryonic development
Chemical Embryology studies chemical and physical events in development, while Teratology focuses on abnormalities and malformations due to genetic events and exogenous factors
Teratology includes the study of birth defects caused by genetic inheritance, mutations, and exogenous factors like drugs, radiation, alcohol, bacteria, and viruses
Phocomelia is a condition where the long bones of the limbs are absent or severely deficient, caused by genetic inheritance, mutations, radiation, or drugs like Thalidomide
Pioneers in Developmental Biology include Aristotle, who defined preformation and epigenesis, and others like Galen, Anton Van Leeuwenhoek, and Marcello Malpighi
A karyotype is a picture of all the chromosomes in a cell, used to identify genetic abnormalities like Down syndrome caused by an extra copy of chromosome 21
August Weissman observed sea urchin’s egg fertilization and cleavage, distinguishing between soma (body) and germ-cell line (gametes), with the zygote containing two nuclei derived from the egg and sperm
HansAdolfEduard Driesch demonstrated the totipotent and pluripotent cell concept, showing that any single monad in the original egg cell was capable of forming any part of the completed embryo
Wilhelm Johannsen distinguished between genotype and phenotype, with genotype being the genetic information acquired from parents and phenotype being the visible appearance or biochemistry at any stage of development
Wilhelm Roux conducted the Ablation Experiment or Embryonic Extirpation, destroying cells in frog embryos to determine if the remaining cell could restore the deficiency during subsequent development, showing the development of the frog is based on a Mosaic mechanism
SalomeGluecksohn Waelsch and Conrad Hal Waddington integrated genetics and embryology, working on mutant genes of mouse and Drosophila to establish Developmental Genetics and Epigenetics