Presentation on theme: "2.E.1 timing and coordination"— Presentation transcript:
1 2.E.1 timing and coordination Read ChapterWatch bozeman science video“timing and coordination”Timing and coordination of specific events are necessary for the normal development of an organism, and these events are regulated by a variety of mechanisms.Draw 6 boxes on your paper
2 The determination of different cell types (cell fates) precedes differentiation and involves the expression of genes for tissue-specific proteins. Tissue-specific proteins enable differentiated cells to carry out specific tasks.
3 Cell differentiation follows determination as the cell continues on a specific developmental path. Differentiation results in cell types such as nerve cells, blood cells, and muscle cells.
4 A single-celled zygote can develop into a multicellular adult organism that contains hundreds of different cell types.
5 Totipotent cells are stem cells that can form all the cell types in a body, plus placental cells. Embryonic cells within the first couple of cell divisions after fertilization are the only cells that are totipotent.
6 Pluripotent cells can give rise to all of the cell types that make up the body; embryonic stem cells are considered pluripotent.
7 The transformation from a zygote into an organism results from three interrelated processes: Cell division: the zygote gives rise to a large number of cells through a succession of mitotic cell divisionsCell differentiation: cells become specialized in structure and functionMorphogenesis: the processes that give shape to the organism and its various parts
8 Box #1Compare cell differentiation and cell division.
9 Genomic Equivalence: Nearly all the cells of an organism have the same genome. Cells differentiate through differential gene expression.
10 Hierarchy of Gene Activity in Early Drosophila Development Observable cell differentiation results from the expression of genes for tissue-specific proteins.Hierarchy of Gene Activity in Early Drosophila DevelopmentMaternal effect genes (egg-polarity genes)Gap genesPair-rule genesSegment polarity genesHomeotic genes of the embryoOther genes of the embryoSegmentation genesof the embryo
12 Box #2Describe the function of tissue specific proteins.
13 Regulation of transcription factors during development results in sequential gene expression. Transcription factors are proteins that bind to specific DNA sequences, thereby controlling the flow of genetic information from DNA to mRNA.
14 Cell signaling helps direct daughter cells down the appropriate pathways, a process called induction. Cells induce neighboring cells to differentiate.4AnteriorEMBRYOPosteriorReceptorSignalproteindaughtercell of 3Will go on toform muscleand gonadsform adultintestine123
15 During induction, signal molecules from embryonic cells cause transcriptional changes in nearby target cells.Early embryo(32 cells)SignaltransductionpathwayNUCLEUSSignalreceptorSignalmolecule(inducer)
16 An inducing signal produced by one cell in the embryo can initiate a chain of inductions that results in the formation of a particular organ.
17 Homeotic genes are involved in developmental patterns and sequences.
18 Box #3Describe how induction can lead to the development of an organism.
19 Hox genes are a group of related homeotic genes that control the body plan of the embryo.
20 Pattern formation in animals and plants results from similar genetic and cellular mechanisms. Pattern formation is the development of a spatial organization of tissues and organs.Occurs continually in plantsIs mostly limited to embryos and juveniles in animals
21 An identical or very similar nucleotide sequence has been discovered in the homeotic genes of both vertebrates and invertebrates.Adultfruit flyFruit fly embryo(10 hours)FlychromosomeMousechromosomesMouse embryo(12 days)Adult mouse
28 Temperature and the availability of water determine seed germination in most plants.
29 Genetic mutations can result in abnormal development. Snake with one limb.
30 Box # 5Describe environmental and mutations effect on development
31 Genetic transplantation experiments support the link between gene expression and normal development.
32 In nuclear transplantation, the nucleus of an unfertilized egg cell or zygote is replaced with the nucleus of a differentiated cell.
33 Experiments with frog embryos have shown that a transplanted nucleus can often support normal development of the egg.Frog embryoFrog egg cellFrog tadpoleLess differ-entiated cellDonornucleustrans-plantedEnucleatedegg cellFully differ-entiated(intestinal) cellMost developinto tadpoles<2% develop
34 In 1997, Scottish researchers cloned a lamb from an adult sheep by nuclear transplantation. Dolly the Sheep
37 In most nuclear transplantation studies, few cloned embryos develop normally.
38 Genetic regulation by microRNAs plays an important role in the development of organisms and the control of cellular functions.
39 MicroRNA (miRNA) are a small, non-coding RNA molecules that function in post-transcriptional regulation of gene expression. They generally bind to their target mRNAs and repress protein synthesis by destabilizing the mRNA.
40 Programmed cell death (apoptosis) plays a role in the normal development and differentiation. Cell signaling is involved in programmed cell death.
41 Example: Morphogenesis of fingers and toes Apoptosis plays a critical role in the sculpting of digits in vertebrate limbs. The death of the cells that would otherwise form inter‐digital webbing enables individual fingers and toes to be formed.Example: Morphogenesis of fingers and toes
42 Example: Development in the nematode C. elegans As early as the four-cell stage in C. elegans, cell signaling helps direct daughter cells down the appropriate pathways. Induction is also critical later in nematode development as the embryo passes through three larval stages prior to becoming an adult. A protein in the outer mitochondrial membrane serves as a master regulator of apoptosis .ZygoteNervoussystem,outerskin, mus-culatureMusculature,gonadsOuter skin,nervous systemGerm line(futuregametes)MusculatureFirst cell divisionTime after fertilization (hours)10HatchingIntestineEggsVulvaANTERIORPOSTERIOR1.2 mmExample: Development in the nematode C. elegans
43 Example: Flower development Floral meristems contain three cell types that affect flower development.CarpelPetalStamenSepalFloral meristemTomato flowerCelllayersL1L2L3Example: Flower development
45 Learning Objectives:LO 2.31 The student can connect concepts in and across domains to show that timing and coordination of specific events are necessary for normal development in an organism and that these events are regulated by multiple mechanisms. [See SP 7.2]LO 2.32 The student is able to use a graph or diagram to analyze situations or solve problems (quantitatively or qualitatively) that involve timing and coordination of events necessary for normal development in an organism. [See SP 1.4]LO 2.33 The student is able to justify scientific claims with scientific evidence to show that timing and coordination of several events are necessary for normal development in an organism and that these events are regulated by multiple mechanisms. [See SP 6.1]LO 2.34 The student is able to describe the role of programmed cell death in development and differentiation, the reuse of molecules, and the maintenance of dynamic homeostasis. [See SP 7.1]