Transcript Genes & Development

Biology, Seventh Edition
Solomon • Berg • Martin
Chapter 16
Genes and
Development
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 16 Genes and Development
• Development of an organism
–Organisms contain many types of cells
specialized both structurally and
metabolically
–All descend from a single zygote
–Development is all changes that occur in life
• Cell determination
–Groups of cells become committed
–Leads to cell differentiation
–Differences among cell types due to
differential gene expression
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Biology, Seventh Edition
CHAPTER 16 Genes and Development
• Nuclear equivalence
• Nuclei of all differentiated cells are
genetically identical
• Different cells express different subsets
of genes
–Somatic cells
–Germ line cells
• Totipotency
–Capability of cells to direct development of
entire organism
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CHAPTER 16 Genes and Development
Vertebrate
cell lineages
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CHAPTER 16 Genes and Development
Cell totipotency
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Biology, Seventh Edition
CHAPTER 16 Genes and Development
Nuclear totipotency
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Biology, Seventh Edition
CHAPTER 16 Genes and Development
• Mouse models to study disease
• Ethically researchers often cannot use
humans as test subjects
• Animal model is used instead
–An example is cystic fibrosis, a genetic
disease
–Gene targeting is used to produce mice
homozygous or heterozygous for cystic
fibrosis
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Biology, Seventh Edition
CHAPTER 16 Genes and Development
• First cloned mammal
• 1997
• Cloned sheep “Dolly” was born in
Scotland
• Genetic material derived from
–Cultured adult sheep’s mammary gland cell
–Fused with enucleated sheep’s egg
–Cultured in vitro and transferred to host
mother
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CHAPTER 16 Genes and Development
Mammalian
cloning
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CHAPTER 16 Genes and Development
• Stem cells
• Undifferentiated cells
• Can produce differentiated descendants
• Also retain ability to reproduce
themselves
• Totipotent stem cells
–Give rise to all cell types
• Pluripotent stem cells
–More specialized
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CHAPTER 16 Genes and Development
• Exceptions to nuclear equivalence
• Genomic rearrangements
–Physical changes in gene structure
• Gene amplification
–More copies of certain genes for
transcription
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CHAPTER 16 Genes and Development
Gene amplification
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CHAPTER 16 Genes and Development
• Choice of organisms for research in
developmental genetics
• Fruit fly, Drosophila melanogaster
–Abundance of mutant alleles and ease of
mapping new mutations on the
chromosomes
• Roundworm, Caenorhabditis elegans
–Lineage of every somatic cell is known
• Laboratory mouse, Mus musculus
–Used in studies of mammalian development
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CHAPTER 16 Genes and Development
Life cycle
of Drosophila
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CHAPTER 16 Genes and Development
Location of imaginal discs in Drosophila
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CHAPTER 16 Genes and Development
• Maternal effect genes
• Genes that organize structure of egg
cells
• Genes in maternal tissues transcribed to
produce mRNA molecules that are
transported in egg
• Analysis of mutant Drosophila revealed
that these genes involved in polarity of
embryo
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CHAPTER 16 Genes and Development
Early development in Drosophila
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CHAPTER 16 Genes and Development
Classes of genes involved in pattern formation of
embryonic segments in Drosophila
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CHAPTER 16 Genes and Development
• Segmentation genes
• Genes that generate a repeating pattern
of body segments within embryo
–Gap genes
–Pair-rule genes
–Segment polarity genes
–Homeotic genes
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CHAPTER 16 Genes and Development
Comparison of mutations in Drosophila
segmented genes
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CHAPTER 16 Genes and Development
Antennapedia Locus
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CHAPTER 16 Genes and Development
Hox
gene clusters
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CHAPTER 16 Genes and Development
• Induction and apoptosis
• Induction in C. elegans
–Developmental interactions with neighboring
cells
–Anchor cell induces surface cells to form vulva
• Apoptosis in humans
–During development, hand forms a webbed
structure
–Fingers become individualized when cells
between them die
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Biology, Seventh Edition
CHAPTER 16 Genes and Development
Caenorhabditis elegans
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CHAPTER 16 Genes and Development
Cell lineages of C. elegans
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CHAPTER 16 Genes and Development
Induction
in C. elegans
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CHAPTER 16 Genes and Development
• Mouse model for mammalian
development
• Transgenic mice studied
• Early development of mice and other
mammals similar
• Almost all research in stages leading to
implantation
• Chimera
–Organism containing two or more kinds of
genetically dissimilar cells from two zygotes
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CHAPTER 16 Genes and Development
Chimeric mice
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CHAPTER 16 Genes and Development
Producing
a transgenic
mouse
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CHAPTER 16 Genes and Development
• Cancer and cell development
• Cancer-causing oncogenes
–Proto-oncogenes
–Code for various growth factors or growth
factor receptors
–Respond to stimulation by growth factors
–Cell may misinterpret signal and grow and
divide inappropriately
• Tumor suppressor gene mutation
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CHAPTER 16 Genes and Development
Cell growth control cascade
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