DEV.BIO PRELIMS

• Grounding:

  • Maternal genes and egg cytoplasm direct initial developmental stages
  • Zygotic genes direct development after cleavage
• Genomic Equivalence:

  • Each cell in the body has the same genetic material
  • All the information necessary to produce a complete organism is present in each cell
• Amphibian Cloning:

  • Restriction of nuclear potency
  • Totipotency: total capacity of a cell to give rise to a complete embryo
  • Pluripotency: ability to give rise to several types of cells, but not all
• Procedure for transplanting blastula nuclei into activated enucleated Rana pipiens eggs:

  • Relative dimensions of the meiotic spindle have been exaggerated to show the technique
  • "Freddy," the mature R. pipiens, was derived in this way by M. DiBerardino and N. Hoffner Orr
• Cloning Mammals:

  • Mammary gland cell nucleus fused with an enucleated oocyte
  • Implanted in a surrogate mother (different breed of sheep) to produce Dolly
• Cell Differentiation:

  • Generation of cellular diversity
  • Process by which a cell becomes different in structure and function
  • Morphological and functional expression of a portion of the genome
  • A cell specialized in one or few synthetic pathways
• Selective Gene Expression:

  • Genes are activated differently depending on time (phase of development) and space (specific cell)
  • Depression of certain genes at different times and in different cells
• Selective Gene Amplification:

  • Transient increase in the number of certain genes without mitosis
  • Adaptive response for meeting the synthetic requirements of the developing egg
  • During the early diplotene stage of meiosis, the nucleoli in the germinal vesicle are active in the synthesis of ribosomal RNA
• Embryonic Induction:

  • Cells induce or influence adjacent cells to change their behavior
  • Embryonic tissue (inductor) influences responding tissue
  • Responding tissue must possess competence to respond to the inducer
  • Induction of neurulation and axis development by the notochord/chordamesoderm
• Morphogenesis:

  • 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
• Cell Proliferation:

  • Characterized by rapid cell divisions resulting in an increase in the number of cells
  • Mitotic divisions
• Cell Migration:

  • Process where cells or groups of cells move from one part of the embryo to another
  • May involve short migrations of individual cells or massive dislocation of groups or sheets of cells over relatively great distances
• Apoptosis:

  • Examples include resorption of the tadpole tail, separation of digits in the embryonic hand and feet, selective cell death of neurons
• Homeotic Genes:

  • Specify the antero-posterior axis and segment identity during early stages of metazoan development
  • Critical for the proper placement of certain embryonic structures like legs, antennae, and eyes
• Homeobox Genes:

  • Sequence of 180 base pairs defining Homeotic genes
  • Homeobox codes for the 61 amino acid protein known as HOMEODOMAIN
  • Many Homeobox genes found in Drosophila melanogaster also found in vertebrates
  • Expressed in highly specific sites and stages of development
• Origin of Chordate:

  • Modularity occurs through discrete and interacting modules (units) like cells, tissues, organs
  • Allows different parts of the body to develop without interfering with other functions
  • Duplication allows the formation of redundant structures, while divergence allows structures to assume new roles
  • Dissociation involves heterochrony and allometry
  • Allometry may involve altering a target cell's sensitivity to growth factors or altering the amounts of growth factors produced
• Developmental Biology merges embryology and genetics, focusing on the development of organisms from a fertilized egg to an adult form
• Developmental Biology explores organogenesis, postnatal development, neoplastic growth, metamorphosis, regeneration, and tissue repair
• 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
• Developmental Biology addresses issues like in-vitro fertilization, embryo transfer, animal cloning, and genetic disease diagnosis
• Cloning is the process of creating genetically identical living beings, with Dolly the sheep being the first cloned animal
• 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
• Hans Adolf Eduard 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
• Regulative Development refers to the ability of an embryo to develop normally even if some cells are removed or rearranged
• 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
• Salome Gluecksohn Waelsch and Conrad Hal Waddington integrated genetics and embryology, working on mutant genes of mouse and Drosophila to establish Developmental Genetics and Epigenetics
• Attachment is a strong reciprocal emotional bond between an infant and a primary caregiver
• Schaffer and Emerson's 1964 study on attachment:

  • Aim: identify stages of attachment / find a pattern in the development of an attachment between infants and parents
  • Participants: 60 babies from Glasgow
  • Procedure: analysed interactions between infants and carers
  • Findings: babies of parents/carers with 'sensitive responsiveness' were more likely to have formed an attachment
• Freud's superego is the moral component of the psyche, representing internalized societal values and standards
• Developmental Biology merges embryology and genetics, studying the development of organisms from a fertilized egg to an adult form