Chapter 50

Chapter 50 - BiologyNotes CHAPTER50 AnimalDevelopment...

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Biology Notes 03/03/2009 15:57:00 CHAPTER 50     Animal Development     Cell Differentiation     o Process by which a cell becomes specialized to carry out specific  functions o The molecular events that lead to cell differentiation involve a process  called cell determination When a cell becomes committed to a certain task/specialization  due to differential gene expression o Not all cells differentiate Stem cells remain in a relatively undifferentiated state Retain the ability to differentiated when needed Stem Cells     o Totipotent Stem Cell The stem cell that has unlimited capability Has the ability to form the extraembryonic membranes  and tissues, the embryo itself, and all postembryonic  tissues and organs Embryo o Ploripotent Stem cells Capable of giving rise to most but not all tissues of an organism Inner mass cell o Multipotent Stem Cells These cells are committed to give rise to cells that have a  specific function
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Blood stem cells Differential Gene Expression     o Various types of differentiated cells have the same genetic information  but express different gene subsets Responsible for variations in their chemistry, behavior, and  structure o Once a cell is differentiated usually no genetic changes occur, nor is  there any loss in genetic information, during either cell determination  and cell differentiation Principle of  nuclear equivalence   Morphogenesis     o Cell differentiation itself cant explain the development of form o Rather, morphogenesis requires the: Progressive organization of tissues and organs Which occurs through  pattern formation o In pattern formation, cells go through: Communication by signaling Planned cell migration Changes shape ECM interaction  Apoptosis  (cell death) Development     The stages of development include: o Fertilization o Cleavage
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o Blastulation o Gastrulation- development of three germ layers (ecto, endo,  mesoderm) o Organogenesis Fertilization     o Contact and recognition Between noncellular egg coverings and sperm o Sperm entry is regulated Prevents interspecific fertilization Prevents  polyspermy  (fertilization of more than one sperm) o Fertilization activates egg Triggering events of early development Metabolic changes Egg nucleus completes meiosis o Once fertilized, sperm and egg Pronuclei fuse Zygote DNA synthesis Fertilization and the meeting of the egg and sperm initiate the development of  form Fertilization has two important gene consequences o Restoration of the diploid chromosome number o Determination of sex of the offspring Describe the four processes involved in fertilization (echinoderms)
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Chapter 50 - BiologyNotes CHAPTER50 AnimalDevelopment...

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