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UNT BIOL 4330 - Exam 1 Study Guide
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Biol 4330 1st EditionExam # 1 Study Guide Lectures: 1 - 6Lecture 1 (Jan 27)Developmental 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. How does a fertilized egg give rise to an adult body? How does that adult body produce yet another adult body?Von Baer’s 4 Laws are 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 agiven 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 likeits 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 structures at a different age and size. The eggs of birds, mammals, reptiles, fish and amphibians start development very differently because of theenormous 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. Evolutionary Embryology – relationships between groups can be established by finding commonembryonic or larval forms. Lecture 2 (Feb 3)Developmental Genetics is the discipline that examines how the genotype is transformed into the phenotype. Many conserved core processes that are responsible for generating most of the anatomy, physiology and behavior of an organism. All evolved between 3 billion and half billion years ago. Includes metabolism, gene expression and signaling between cells. Complexity of an organism must arise through the multiple use of a few conserved elements. Core processes are linked to one another. Linkage –regulatory linkage means how information is passed from one component to another (how one molecule passes information to another).The Monod Experiment: discovered the process of gene expression- a core process for generating phenotypic variation. Understanding embryonic development is central for explaining phenotypic novelty in animals. Understanding embryonic development is central for explaining phenotypic novelty in animals. Most of the phenotypic and physiological complexity is established in the embryo. Every new gene in evolution must somehow be linked to a transcriptional regulatory program, and old genes continue to undergo changes of regulation.Genomic Equivalence : each somatic cell nucleus has the same set of Xsomes and genes (or genome). Evidence for these includes cloning a mammal using nuclei from adult somatic cells. Every cell nucleus contains the complete genome established in the fertilized egg. In molecular terms, the DNAs of all differentiated cells are identical. The unused genes in differentiated cells are either destroyed nor mutated, but retain the potential for being expressed. Only a small percentage of the genome is expressed in each cell, and a portion of the RNA synthetized in each cell is specific for that cell type. Differential gene transcription- regulates which of the nuclear genes are transcribed into nuclear RNA. Selective nuclear RNA processing- regulates which of the transcribed RNAs (or nuclear RNAs) are able to enter into the cytoplasm and become mRNAs. Selective messenger RNA translation – regulates which of the mRNAs in the cytoplasm are translated into proteins. Differential protein modification- regulates which proteins are allowed to remain and/or function in the cell. Enhancers are DNA sequences that control the efficiency and rate of transcription from a specific promoter.Most genes require enhancers for their transcription. Enhancers are the major determinant of differential transcription in space (cell type) and time. Enhancers can function far from the promoter and each enhancer can be bound by more than one transcription factor. Interaction between TFs bound to enhancer sites and transcription initiation complex assembled at the promoter is thought to regulate transcription. Enhancers are combinatorial; various DNA sequences regulate temporal and spatial gene expression and these can be mixed and matched.Enhancers are modular. A gene can have several enhancer elements, each of which turns it on a different set of cells. Enhancers generally activate transcription by one of two means: they either remodel chromatin to expose the promoter, or they facilitate the binding ofRNA polymerase to the promoter by stabilizing TAFs. Enhancers also inhibit transcription…these are called silencers. The bridge between enhancer and promoter can be made by transcription factors. The genetic elements regulating tissue-specific transcription can be identified by fusing reporter genes to suspected enhancer regions of the genes expressed in particular cell types. The gene for GFP is fused to a lens crystallin enhancer gene in Xenopus and the result is the expression of GFP in the tadpole lens. Enhancer region of the muscle-specific protein Myf-5 protein is fused to β-galac. Reporter gene and injected into the mouse embryo-lights up darkly stained muscle areas.The genetic elements regulating tissue-specific transcription can be identified by fusing reportergenes to suspected enhancer regions of the genes expressed in particular cell types. Genes for specific proteins use numerous TFs in various combinations. Enhancers are modular (e.g. Pax6 gene is expressed in the eye, pancreas & nervous system). TFs are proteins that bind to enhancer or promoter regions and interact to activate or repress the transcription of a particular gene. Most TFs can bind to specific DNA sequences. TFs can be


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UNT BIOL 4330 - Exam 1 Study Guide

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