Slide 1 : The Genetic Basis of Development
Slide 2 : Overview: From Single Cell to Multicellular Organism
The application of genetic analysis and DNA technology
Has revolutionized the study of development
Slide 3 : Researchers
Use mutations to deduce developmental pathways
Have applied the concepts and tools of molecular genetics to the study of developmental biology
Slide 4 : When the primary research goal is to understand broad biological principles
The organism chosen for study is called a model organism Figure 21.2
Slide 5 :
Slide 6 : Concept 21.1: Embryonic development involves cell division, cell differentiation, and morphogenesis
In the embryonic development of most organisms
A single-celled zygote gives rise to cells of many different types, each with a different structure and corresponding function
Slide 7 : The transformation from a zygote into an organism
Results from three interrelated processes: cell division, cell differentiation, and morphogenesis
Slide 8 : Through a succession of mitotic cell divisions
The zygote gives rise to a large number of cells
In cell differentiation
Cells become specialized in structure and function
Morphogenesis encompasses the processes
That give shape to the organism and its various parts
Slide 9 :
Slide 10 : Concept 21.2: Different cell types result from differential gene expression in cells with the same DNA
Differences between cells in a multicellular organism
Come almost entirely from differences in gene expression, not from differences in the cells’ genomes
Evidence for Genomic Equivalence : Evidence for Genomic Equivalence Many experiments support the conclusion that
Nearly all the cells of an organism have genomic equivalence, that is, they have the same genes
Totipotency in Plants : Totipotency in Plants One experimental approach for testing genomic equivalence
Is to see whether a differentiated cell can generate a whole organism
Slide 13 :
Slide 14 : A totipotent cell
Is one capable of generating a complete new organism
Cloning
Is using one or more somatic cells from a multicellular organism to make another genetically identical individual
Nuclear Transplantation in Animals : Nuclear Transplantation in Animals In nuclear transplantation
The nucleus of an unfertilized egg cell is replaced with the nucleus of a differentiated cell
Slide 16 : Experiments with frog embryos
Have shown that a transplanted nucleus can often support normal development of the egg
Slide 17 :
Slide 18 : Reproductive Cloning of Mammals
In 1997, Scottish researchers
Cloned a lamb from an adult sheep by nuclear transplantation
Slide 19 :
Slide 20 : “Copy Cat”
Was the first cat ever cloned
Slide 21 : Problems Associated with Animal Cloning
In most nuclear transplantation studies performed thus far
Only a small percentage of cloned embryos develop normally to birth
The Stem Cells of Animals : The Stem Cells of Animals A stem cell
Is a relatively unspecialized cell
Can reproduce itself indefinitely
Can differentiate into specialized cells of one or more types, given appropriate conditions
Slide 23 : Stem cells can be isolated
From early embryos at the blastocyst stage
Slide 24 : Adult stem cells
Are said to be pluripotent, able to give rise to multiple but not all cell types
Transcriptional Regulation of Gene Expression During Development : Transcriptional Regulation of Gene Expression During Development Cell determination
Precedes differentiation and involves the expression of genes for tissue-specific proteins
Tissue-specific proteins
Enable differentiated cells to carry out their specific tasks
Slide 26 : Determination and differentiation of muscle cells Figure 21.10
Cytoplasmic Determinants and Cell-Cell Signals in Cell Differentiation : Cytoplasmic Determinants and Cell-Cell Signals in Cell Differentiation Cytoplasmic determinants in the cytoplasm of the unfertilized egg
Regulate the expression of genes in the zygote that affect the developmental fate of embryonic cells Sperm Molecules of
another cyto-
plasmic deter-
minant Sperm
Slide 28 : Concept 21.3: 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 plants
Is mostly limited to embryos and juveniles in animals
Slide 29 : Positional information
Consists of molecular cues that control pattern formation
Tells a cell its location relative to the body’s axes and to other cells
Programmed Cell Death (Apoptosis) : Programmed Cell Death (Apoptosis) In apoptosis
Cell signaling is involved in programmed cell death
Slide 31 : In C. elegans, a protein in the outer mitochondrial membrane
Serves as a master regulator of apoptosis
Slide 32 : In vertebrates
Apoptosis is essential for normal morphogenesis of hands and feet in humans and paws in other animals
Plant Development: Cell Signaling and Transcriptional Regulation : Plant Development: Cell Signaling and Transcriptional Regulation Thanks to DNA technology and clues from animal research
Plant research is now progressing rapidly
Mechanisms of Plant Development : Mechanisms of Plant Development In general, cell lineage
Is much less important for pattern formation in plants than in animals
The embryonic development of most plants
Occurs inside the seed
Slide 35 : Concept 21.4: Comparative studies help explain how the evolution of development leads to morphological diversity
Biologists in the field of evolutionary developmental biology, or “evo-devo,” as it is often called
Compare developmental processes of different multicellular organisms
Widespread Conservation of Developmental Genes Among Animals : Widespread Conservation of Developmental Genes Among Animals Molecular analysis of the homeotic genes in Drosophila
Has shown that they all include a sequence called a homeobox
Slide 37 : An identical or very similar nucleotide sequence
Has been discovered in the homeotic genes of both vertebrates and invertebrates
Slide 38 : Related genetic sequences
Have been found in regulatory genes of yeasts, plants, and even prokaryotes
In addition to developmental genes
Many other genes involved in development are highly conserved from species to species
Slide 39 : In some cases
Small changes in regulatory sequences of particular genes can lead to major changes in body form, as in crustaceans and insects
Slide 40 : In other cases
Genes with conserved sequences play different roles in the development of different species
In plants
Homeobox-containing genes do not function in pattern formation as they do in animals
Comparison of Animal and Plant Development : Comparison of Animal and Plant Development In both plants and animals
Development relies on a cascade of transcriptional regulators turning genes on or off in a finely tuned series
But the genes that direct analogous developmental processes
Differ considerably in sequence in plants and animals, as a result of their remote ancestry
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