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UNT BIOL 4330 - Intro to Developmental Biology

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BIOL 4330 1st Edition Lecture 1 Outline of Current Lecture I. Intro to Developmental BiologyII. Approaches to Developmental BiologyIII. MorphogenesisIV. Selectable VariationCurrent LectureDevelopmental biology studies the initiation and construction of organisms rather than their maintenance.Developmental biology is an integrative field: it goes from the molecular / chemical levels, through the cellular and organ systems to the ecological and evolutionary levels.Two fundamental questions in developmental biology:1. How does a fertilized egg give rise to an adult body?2. How does that adult body produce yet another adult body?Questions in Developmental Biology- Differentiation- Morphogenesis- Growth- Reproduction- Regeneration- Evolution- Environmental IntegrationA Frog’s Life1. Gametogenesis & Fertilization2. Cleavage and Gastrulation3. Organogenesis4. Metamorphosis & GametogenesisThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Life CycleFertilization forms the 3 axes of the embryo:1) Anterior-posterior (head-tail)2) Dorsal-ventral (back-belly)3) Left-rightThree Strands of the Anatomical Approach- Comparative embryology- Evolutionary embryology- TeratologyThree Approaches to Developmental Biology- Anatomical- Experimental- GeneticThe dividing cells of the fertilized egg form three distinct embryonic germ layers.Von Baer’s 4 Laws (before Darwin’s Theory of Evolution)1. The general features appear earlier in development than specialized features. All vertebrate embryos have gill arches, spinal chords, and primitive kidney.2. Less general develop from more general, until finally the most specialized appear.3. The embryo of a given species, instead of passing through adult stages of lower animals departs more and more from them.4. Therefore, an embryo of a higher animal is never like a lower animal, but only like its embryo.Two types of microscopy are used to visualize the notochord and its separation of vertebrate embryos (in this case a chick) into right and left halves.All animals begin with a basically similar structure although they develop, acquire the structuresat a different age and size.The eggs of birds, mammals, reptiles, fish and amphibians start development very differently because of the enormous differences in the sizes of their eggs.Ontogeny does not recapitulate phylogeny. Human embryos never pass through a stage equivalent to an adult fish or bird. Rather, human embryos initially share characteristics in common with fish and avian embryos. Later, the mammalian and other embryos diverge, none of them passing through the stages of others.Two types of cells in the embryo:Epithelial cells tightly connected to one another in sheets or tubes.Mesenchymal cells unconnected to one another and operate and independent units.Major morphogenetic processes are regulated by mesenchymal and epithelial cells.Morphogenesis happens by:- Direction and number of cell divisions- Cell shape changes- Cell movement- Cell growth- Cell death- Changes in the composition of the cell membrane or secreted productsEvolutionary Embryology – relationships between groups can be established by finding commonembryonic or larval forms.Selectable variation of dachshunds through mutations of genes that work during development:1) Breeders select for small legs – results from premature cessation of cell division in the limb cartilage precursor cells – early activation of the cartilage FGF receptor protein – the Dachshund has an extra copy of the Fgf4 gene2) Longhaired dachshunds have an additional mutation, a truncated Fgf5 gene which alters the hair follicle cycle allowing the hair growth beyond wild type


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