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BIOL 3P28 Exam 1 notes.docx

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Robert Carlone

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BIOL 3P28 – Exam Notes 1 Midterm st Development 1. FERTILIZATION -- diploid zygote  Fusion of gamete nuclei (1/2 of normal chromosomes) gives a complete genome  Exocytosis releases onto oocyte to digest egg surface to enter zona pellucida  Fertilization accomplishes: restoration of the diploid state & activation of the eggs developmental potential 2. CLEAVAGE  Rapid mitotic division following fertilization  Cytoplasm divides into blastomeres  blastula (sphere shaped)  Blastula has same volume as original zygote, the cells are just getting smaller through division (normal cell size)  Has fluid filled cavity on 1 side  Has polarity  Vegetal pole – has yolk, slowly divides, immobile, used for food  Animal pole – upper half, cells divide rapidly, become mobile i. Where the blastocoels forms (fluid starts to flow inside cavity) ii. Allows cell mov’t to occur for gastrulation  Hollow areas allows for cell migration  Blastocyst – embryo 64 cells, seperates into 2 types i. Trophectoderm (TE) – form extra-embryonic tissues (ex/placenta) ii. Inner cell Mass (ICM) – forms embryo proper, source of ES cells 3. GASTRULATION  Blastula moves position  Results in 3 germ layers - Trilaminar – ectoderm, mesoderm, endoderm  One of the most critical periods  Begins w/a slit (becomes blostopore)  Occurs at blastopore – 180 from sperm entry (becomes mesoderm)  Neural folds form (dorsal) neural tube 4. ORGANOGENESIS  Formation of organs from cell interaction of germ layer st  Notochord signals differentiation into  1 CNS – from neural epithelium  A neural tube forms & mesodermal tissues become somites  Cells migrate to final location 5. METAMORPHOSIS  Undergoes sexual maturity from larva to adult MESODERM - From cells migrating through the blastopore - Inner layer b/w Ecto&Endoderm - Connective tissue, blood, heart, skeleton ECTODERM - Outer layer, encloses embryo (Skin, brain, nerves) ENDODERM - Cells from vegetal hemisphere are enclosed by ectoderm to become endoderm - Gut& respiratory system - On inside of embryo Morphogenesis = differentiation controlled by nucleus MEIOSIS – makes fertilization possible 1. Chromosomes replicate prior to cell division 2. Cstomosomes (chromatid) are held together by kinetochores 3. 1 division – chromatids separate 4. 2 division – splits kinetochore – each chromatid becomes a chromosome 5. Results in 4 germ cells with haploid nucleus Asymmetric cell division – 2 different daughter cells are formed Symmetric divisions -- both daughter cells formed are identical, may have different fates Totipotent cells -- ability of a single cell to divide and produce all the differentiated cells Germ-line cells -- give rise to eggs or sperm - Set aside for reproduction - Migrate to gonads & complete meiosis Somatic cells -- All other cells - Give rise to the individual body - One of the 1 differentiations Zygote—totipotent, single cell, can generate every cell in the body and placental cells for embryo, fertilized egg is dipoloid Multipotent – in adults, can give rise to some stem cells but not all (Controlled by Sox2) Embryology – study of animal devl’p Devl’p biology – studies embryonic & other devl’p process Oviparity – egg birth Vivaparity – live birth Ovovivparity – egg that hatches in body Formation of the Neural Tube (brain/spinal cord)  Part of ectoderm rolls up and seperates from other cells  Forms epidermis and neural tube  Neural crest cells form then migrate out  Notochord provides information for neural tube -- discovered by vonBaer o Seperates embryo into left/right half o Becomes the nervous system  Neural tube fills with fluid forming the subventricular zone & neural stem cells  NSC will form neuron and layers of the nervous system VonBaers Laws 1. General features appear before specialized feature a. All embryos have same early features 2. Less general features develop from more general 3. An embryo of a given species departs more from lower animals 4. The early embryo of a higher animal is never like a lower animal – only like its early embryo metaplasia (transdifferentation) – transformation of cell from one type to another Gene -- entire DNA sequence required for synthesis of a protein or RNA molecule Exon – coding sequence Intron – non-coding sequence removed, removed from RNA by RNA splicing, 25.9% of human genome Chromosome –condensed chromatin miRNA (micro RNA) – regulates translation and stability of mRNA chromatid – 1 copy of replicated chromosome, joined to another copy (sister chromatid) – separate during mitosis Fate Maps – track cell lines Genomic equivalence – each somatic cell nucleus has the same chromosomes & genes as all other somatic nuclei (descendants) epigenesis --‐ organs formed de novo (from scratch) --‐ (Aristotle, Harvey) preformation -- preformed within egg or sperm Malpighi – “un--‐incubated” chick egg already had significant form. Pander – discovered the 3 germ layers – also that they didn’t evolve independently Morphogenesis processes epithelial cells – tightly connected – cells in embryo Mesenchymal cells – unconnected & independent – cells in embryo 1. Direction & # of cell divisions 2. Cell shape changes, movement, growth & death Techniques for studying Embryos 1. Observe live embryos 2. Vital dye staining – stains doesn’t kill 3. Radioactive labeling & fluorescent dyes 4. Genetic marking 5. Cell migration Differentiation - Each cell has the same info in its genome it is expre
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