Developmental Biology Lu 1

• If cells with different adhesion systems are mixed they will sort out into separate zones.
• Growth and Death are classified as morphogenetic processes.
• Developmental Biology has been one of the most exciting areas of biological research since the 1980s, with advances from three main concepts: Experimental Embryology, Developmental Genetics, and Molecular Biology.
• Experimental embryology, which focuses on Embryonic Induction, flourished in the late 1970s when mass genetic screens were carried out on the fruitfly and thousands of mutations were examined.
• Developmental genetics, which identifies a high proportion of the genes that control development, not just in Drosophila, but in all animals, flourished in the late 1970s.
• Molecular biology, which started with the discovery of the 3D of DNA in 1953, became a practical science of gene manipulation in the 1970s.
• Developmental Biology unites the disciplines of molecular biology, cell biology, genetics, and morphology.
• In vitro fertilization (IVF) is now a routine procedure and has enabled many previously infertile couples to have a baby.
• Other technologies such as artificial insemination by donor (AID), egg donation, cryopreservation, embryo transfer, and the science of teratology study the effects of environmental agents such as chemicals, viral infection, or radiation on embryos.
• Understanding of the chromosomal basis of some human birth defects is a common feature of developmental biology.
• Understanding of developmental mechanisms will assist the pharma industry in designing drugs against cancer and degenerative diseases.
• The in vivo function of many signal transduction pathways can be visualized in Xenopus or zebrafish or Drosophila or Caenorhabditis elegans.
• Possibility of using our understanding of growth and regeneration processes for therapy is a common feature of developmental biology.
• Embryonic stem cells and tissue engineering are common features of developmental biology.
• Development happens most obviously in the course of embryonic development as the fertilized egg develops into a complete organism.
• Concepts in development can be loosely classified into four groups: Regional specification, Cell differentiation, Morphogenesis, and Growth.
• In any animal the sperm and eggs and their precursor cells are known as the germ line, while all other cell types are called somatic cells.
• Exceptions to genomic equivalence include antibody forming genes of B lymphocytes and the T-cell receptor genes of T lymphocytes, which undergo rearrangement at the DNA level, and certain nematodes, which shed chromosomes from some cell lineages during development.
• Polyploidy, where the whole chromosome set is doubled or quadrupled, can occur in some mammalian tissues such as the liver.
• After the germ cells arrive they become fully integrated, and in postembryonic life undergo gamete formation or gametogenesis.
• Gastrulation then converts the simple ball or sheet of cells into a three-layered structure known as the gastrula.
• The frontal plane is often, but not necessarily, the plane of the second cleavage.
• Cadherins are major adhesion components.
• Any vertical plane, corresponding to circles of longitude, is called a medial plane.
• Each gamete derived from germ cell contributes a haploid (1n) chromosome set so the zygote is diploid (2n).
• Vertebrate epithelial cells are bound together by tight junctions, adherens junctions, and desmosomes.
• This is the stage of maternal effects where embryonic cleavage stage depend entirely on the genotype of the mother.
• During embryonic development germ cells undergo a period of multiplication and migrate from the site of their formation to the gonad.
• Polyteny, where DNA replication occurs repeatedly without chromosomal division, leading to giant chromosomes, occurs in some tissues in Drosophila.
• Cell shape changes and movements are fundamental to early development.
• Animal embryo is small, spherical and polarized.
• The top-bottom axis is called dorsoventral and the left-right axes are called mediolateral.
• During the cleavage phase a cavity usually forms in the center of the ball of cells due to uptake of water and becomes known as the blastocoel.
• Blastula, the cells are being bound by cadherins, and will usually have a system of tight junctions forming a seal between the external environment and the internal environment of the blastocoel.
• In human anatomy, because we stand upright on two legs, the term anteroposterior is normally synonymous with dorsoventral.
• Ectoderm, Endoderm and Mesoderm are the three layers of the gastrula.
• The upper hemisphere, usually carrying the polar bodies, is called the animal hemisphere, and the lower hemisphere, the vegetal hemisphere.
• If the animal and vegetal poles are at the top and bottom, then the equatorial plane is the horizontal plane dividing the egg into animal and vegetal hemispheres.
• The terms proximal and distal are usually used in relation to appendages, proximal meaning “near the body” and distal meaning “ further away from the body.”
• The early cell divisions are called cleavages with the product called blastomeres.