BIOL 118 1st Edition Exam 3 Chapters 22 24 42 46 Chapter 22 Most cells stop proliferating at maturity but there are some specialized undifferentiated cells that continue to proliferate o Meristems plants Can give rise to various structures o 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 differentiation o Cell differentiation does not involving the change of genetic makeup but differential gene expression Genes are regulated at multiple levels transcription RNA processing translation posttranslation 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 axis o 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 segments o Gap genes define the general position of segments in the anterior middle or posterior of the body o Pair rule genes demarcate the boundaries of individual segments o Segment polarity genes delineate boundaries within individual segments Hox genes identify each segment s structural role o Trigger structure development o 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 genes Hox genes Effector genes Chapter 23 Fertilization occurs when haploid sperm egg fuse forming a diploid zygote fertilized egg o Sperm heads bind to jelly layer of egg o Acrosome reaction releases sperm contents o 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 can only work for same species Polyspermy fertilization by more than one sperm o 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 fertilization o 1st step in embryogenesis makes single celled zygote into multicellular embryo o Blastomeres created by cleavage divisions mass of blastula o Occurs in oviduct connects ovary to the uterus o 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 gastrula o Tissues are arranged in layers o Gut forms o Major body axes become visible Organogenesis process of tissue organ formation o 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 cord o 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 cells o Myoblast cell that is determined to become a muscle cell but has not begun producing muscle specific proteins o MyoD protein that causes muscle cell differentiation Regulatory transcription factor Steps o Fertilization triggers cleavage blastocyst o Blastocyst triggers gene cascades potential changes during gastrulation o Notochord signals specific somite cells to begin MyoD production targeting these cells to specific muscles o Muscle cells begin expressing muscle specific proteins Chapter 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 organs o Leaves o Roots o 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 hypocotyl o Make up shoot aboveground portion of plant body o Roots forms belowground portion Meristem undifferentiated cells that divide repeatedly o Shoot apical meristem SAM tips of shoots o Root apical meristem RAM tips of roots 3 embryonic tissues are produced o Epidermis outer protective covering o 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 molecule o Produced in SA o Part of regulatory cascade that triggers monopteros production apical basal axis Plants adjust to changing environmental conditions through continuous growth development of roots stems leaves Plant body development is driven by meristems Leaf development depends on concentration of
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