BIOL 118 1st EditionExam # 3 Chapters 22-24; 42-46Chapter 22- Most cells stop proliferating at maturity but there are some specialized undifferentiated cells that continue to proliferateo Meristems: plants Can give rise to various structureso Stem cells: animals Give rise to specialized cell types- Cells interact with one another using signals- Cells can move past one another within a block of animal cells- drastic change in embryo shape- Cells can break away from animal cell block &migrate to a new location- Plant cells can regulate plane of cell division &expand in specific directions- don’t move but can change the orientation- Gastrulation: animal cells in different parts of an early embryo rearrange themselves into 3 distinctive types of embryonic tissue that later form specific organs- Apoptosis: programmed cell death- Differential gene expression: expression of different genes in different cell types- key to cell differentiationo Cell differentiation does not involving the change of genetic makeup, but differential gene expression- Genes are regulated at multiple levels: transcription, RNA processing, translation & post-translation- Fate of a cell depends on timing and spatial location- 3 major body axes:o Anterior (head)- posterior (tail)o Ventral (belly) – dorsal (back)o Left- right- Pattern formation: series of events that determine the spatial organization of an embryo- Bicoid: Tells cells where they are located on anterior-posterior axiso Lack of causes most dramatic mutation structures on anterior replaced with posterior structures (literally ass face hahahaahaahah)o In situ hybridization: process to determine the location of bicoid mRNA in the egg- Auxin: triggers the production of transcription factors that affect differentiation- uses concentration gradient- Segment: Distinct region of an animal body that contains a distinct set of structures & is repeated along its length- Segmentation Genes: organize cell & tissues into distinct segmentso Gap genes: define the general position of segments in the anterior, middle or posterior of the bodyo Pair-rule genes: demarcate the boundaries of individual segmentso Segment polarity genes: delineate boundaries within individual segments - Hox genes: identify each segment’s structural role o Trigger structure developmento Homeosis: occurs when cells get incorrect information about where they are in the body- Morphogens: early signal that activates genes that sends signals about spatial location of cells- Regulatory Cascade: Morphogens Gap genes Pair-rule genes segment polarity genesHox genes Effector genesChapter 23- Fertilization: occurs when haploid sperm & egg fuse forming a diploid zygote (fertilized egg)o Sperm heads bind to jelly layer of eggo Acrosome reaction- releases sperm contentso Flagella activity ramps up & sperm penetrates egg coat- Bindin: protein on the head of sperm that binds it to surface of eggs (acts as a key so canonly work for same species)- Polyspermy: fertilization by more than one spermo Fertilization envelope: keeps away additional sperm (sea urchins)o Cortical granules modify egg-cell receptors, preventing additional sperm binding- Cleavage: set of rapid cell divisions that take place in zygotes immediately after fertilizationo 1st step in embryogenesis: makes single-celled zygote into multicellular embryoo Blastomeres: created by cleavage divisions (mass of: blastula)o Occurs in oviduct: connects ovary to the uteruso Blastocyst: specialized blastula consisting f 2 populations of cells External, thin-walled hollow trophoblast surrounds the inner cell mass (ICM) ICM contains cells that undergo gastrulation- Gastrulation: extensive & highly organized cell movements radically rearrange the embryonic cells (gastrula)o Results in 3 primary tissue layers (germ layers): Ectoderm (outer) Mesoderm (middle) Endoderm (inner)o Blastocoel: fluid filled space in gastrulao Tissues are arranged in layerso Gut formso Major body axes become visible- Organogenesis: process of tissue & organ formationo Cells become differentiated (specialized cell type)o Notochord appears in dorsal mesoderm Unique to chordates (vertebrates) Key organizing element Triggers reorganization of dorsal ectodermal cells & forms neural tube- Precursor to brain and spinal cordo Mesodermal cells organize into blocks of tissues called somites Form on both sides of neural tube Form a variety of structures that aren’t initially determined- Determination: somite cells differentiate in response to signals from nearby tissues- Muscle cellso Myoblast: cell that is determined to become a muscle cell but has not begun producing muscle-specific proteinso MyoD: protein that causes muscle cell differentiation Regulatory transcription factor- Steps:o Fertilization triggers cleavage= blastocysto Blastocyst triggers gene cascades- potential changes during gastrulationo Notochord signals specific somite cells to begin MyoD production, targeting these cells to specific muscleso Muscle cells begin expressing muscle specific proteinsChapter 24- Gametogenesis: gamete formation- Fertilization: occurs when sperm & egg combine in a womb-like ovule inside the protective female reproductive structure of a flower - Embryogenesis: continuation of development and ends with maturation of ovule into seed- Germination: forms seedling- Organogenesis: becomes an adult with vegetative organso Leaves o Rootso Stems- Basal (bottom): gives rise to suspensor: anchors embryo as it develops- Apical (top): gives rise to mature embryo- Apical-basal axis: top & bottom- Radial axis: inside & outside- created in globular state- Cotyledons (initial leaves) are connected to root by stem-like hypocotylo Make up shoot aboveground portion of plant bodyo Roots forms belowground portion- Meristem: undifferentiated cells that divide repeatedly o Shoot apical meristem (SAM): tips of shootso Root apical meristem (RAM): tips of roots- 3 embryonic tissues are producedo Epidermis: outer protective coveringo Ground tissue: mass of cells that may later differentiate into specialized cells for photosynthesis, food storage etc.o Vascular tissue: in center of plant; differentiate into specialized cells that transport food & water between root & shoot- Monopteros: gene that is critical in setting up apical-basal axis- Auxin: cell-to-cell signal moleculeo Produced in SAo Part of regulatory cascade that triggers monopteros production &
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