Presentation on theme: "BIO 127 – Developmental Biology Fall 2011 Dr. Tom Landerholm Humboldt Hall 211E 916-278-6152 Office Hours: Wednesday 1:00-2:00, Thursday."— Presentation transcript:
BIO 127 – Developmental Biology Fall 2011 Dr. Tom Landerholm email@example.com Humboldt Hall 211E 916-278-6152 Office Hours: Wednesday 1:00-2:00, Thursday 2:00-4:00 (or by appointment)
Course Organization Section I: Developmental Terms and Processes Section II: Early Development Section III: Development of Organ Systems I Section IV: Development of Organ Systems II Section V: Late Development and Other Topics Labs are designed as extensions of the lectures – Exams will cover both together as a unit
Grades will be based on the result of four exams, 8 laboratory write-ups, the presentation of your poster and participation in the lab as follows: A(-) > 90%, B(+) > 80%, C(+) > 70%, D(+) > 60%, and F < 60% Exam 1Friday09/16100 points Exam2Friday 10/07100 points Exam3Friday 10/28100 points Exam4Friday 11/18100 points Exam5Wed.12/14100 points Lab Write-ups 8 total 200 points Project presentation12/09 50 points Total Points 750
Bio 127 - Section I Developmental Terms and Processes The Big Picture Developmental Anatomy Gilbert 9e – Chapter 1
What are we studying? The COMPLEX PROCESS: one cell to one hundred trillion cells, over 200 cell phenotypes in humans The KEY BIOLOGICAL TRANSITION: genetic inheritance to phenotypic expression The SPECIES COMPARISON: all early animal embryos are similar, the earlier the mutation the bigger the potential change
A VERY COMPLEX PROCESS Most fields of Biology study the adult – Anatomy, Physiology, Genetics, Molecular Biology One cell to one hundred trillion cells – very tightly regulated cell division and death Devo produces 200+ cell types in humans – nearly every one has the same genotype – how do they express different genes so they can change? Cells, tissues, organs, systems, regulation???
The three embryonic germ layers Just a few of the 200+ cell types......
Fig. 13-6 Key Haploid (n) Diploid (2n) n n Gametes n n n Mitosis MEIOSIS FERTILIZATION MEIOSIS 2n2n 2n2n Zygote 2n2n Mitosis Diploid multicellular organism Animals Spores Diploid multicellular organism (sporophyte) Plants and some algae 2n2n Mitosis Gametes Mitosis n n n Zygote FERTILIZATION n n n Mitosis Zygote Most fungi and some protists MEIOSIS FERTILIZATION 2n2n Gametes n n Mitosis Haploid multi- cellular organism (gametophyte) Haploid unicellular or multicellular organism Sexual Life Cycles
THE KEY BIOLOGICAL TRANSITION Genetic inheritance to phenotypic expression – XX = female adult, XY = male adult (in some organisms) – Globin genes carry mutation for sickle cell – Gigantism can be caused by mutations in -subunit of G-protein G s9 Developmental Biologist wants to know..... – What’s on the X and Y chromosome? – When is it expressed? How does it change sex? – Why are globin genes expressed only in RBC? Why does it persist? – -subunit of G-protein G s9 - how does that cause large size?
THE SPECIES COMPARISON Much is learned from studying organisms that develop the same way, as well as those that do it differently Such as... All early animal embryos are similar The earlier a mutation, or other event, occurs, the bigger the potential change
Figure 1.10 Similarities and differences among vertebrate embryos during development
Sometimes the adults are quite different but the embryos give away the closeness of two species
Figure 1.19 Homologies of structure among human arm, seal forelimb, bird wing, and bat wing
Some more key ideas Developmental Mechanisms of Regeneration Development’s Role in Evolution The Impact of the Environment on Developing Organisms
Bio 127 - Section I Introduction to Developmental Biology Developmental Anatomy Gilbert 9e – Chapter 1
Fertilization Birthing (hatching) Maturity Death Fertilization Birthing (hatching) embryogenesis post-embryonic development gametogenesis post-embryonic devo and senescence
The frog is a classic model organism Frog Post-Embryonic Development is very different from ours
Figure 1.2 Early development of the frog Xenopus laevis CLEAVAGE BLASTULATION FERTILIZATION EGG = GAMETE animal vegetal The result is a “blastula”
GASTRULATION FORMS THE GERM LAYERS ORGANOGENESIS neurulation marks the beginning of organogenesis “gastrula” “neurula” the tadpole is a “larva”
Figure 1.4 Metamorphosis of the frog POST-EMBRYONIC DEVELOPMENT: METAMORPHOSIS
Fig. 13-5 Haploid gametes Egg Sperm MEIOSISFERTILIZATION Multicellular adults Diploid Zygote The Human Life Cycle -Embryogenesis -Post-Embryonic Development -Senescence
ART AND ANATOMY ARE THE BACKBONE OF UNDERSTANDING DEVELOPMENT The greatest progressive minds of embryology have not looked for hypotheses; they have looked at embryos.........Jane Oppenheimer 16721908 1817 1981
Drawing is still a very important skill in Developmental Biology but this semester we will employ the digital technologies that are available to us to generate the critical visual communications required to learn DB. - Digital cameras - Image software - Google Images - University websites - Wikipedia - Sac CT
Like all of our sciences, Developmental Biology, had to wade through a time before we knew about cell and molecular biology and digital communications. – No doubt there are other discoveries coming that will change how we view these processes in the future. – We’ll study it in the context of what we know now. (Don’t let that stop you from being amazed by the genius of Aristotle!)
This class is going to teach you a LOT of terminology! Let’s start with some Aristotle classics...... Oviparity = hatched from an egg (birds, amphibians, most reptiles and fish, inverts) Viviparity = born live (placental mammals, some fish and reptiles) Ovoviviparity = born live from eggs hatched in mom (!) (sharks, some reptiles) What is the platypus?
Aristotle Plus Modern Biology... 1. everybody’s born from an egg and 2. cleavage is the first developmental stage after fertilization of that egg, so... meroblastic cleavage = some of the egg cell divides to embryo cells, while some just goes for nutrition holoblastic cleavage = all of the egg cell divides to cells, some embryonic and some extraembryonic
Remember: The Germ Layers formed during gastrulation This is one of the major morphological determinants of taxonomy in Animalia. Of the nine phyla in the kingdom, 7 are triploblastic and 2 are diploblastic.
The Blastopore formed during gastrulation This is another key taxonomic determinant: 2 phyla of 9 in Animalia form the anus here, the rest form the mouth at the blastopore. deuterostomes v. proteostomes
The Notochord Only members of phylum Chordata make a notochord. (of the three sub-phyla, only Vertebrata makes a spine out of it.)
Evolution of pharyngeal arches in the vertebrate head This is also a characteristic found only in Chordata. early embryoadult fish adult reptilehuman
von Baer’s Laws: 1. The general features of a large group of animals appear earlier in development than do the specialized features of a smaller group. 2. Less general characters develop from the more general, until finally the most specialized appear 3. The embryo of a given species, instead of passing through the adult stages of lower animals, departs more and more from them. 4. Therefore, the early embryo of a higher animal is never like a lower animal, but only like its early embryo.
Keeping Track of Moving Cells in the Embryo – A key difference between embryos and adults is cell movement Nearly all embryo cells are on the move Only limited types of cells move in the adult -There are two types of moving cells in the embryo -Epithelial cells adhere to each other, move as a group -Mesenchymal cells live and move as individuals
Tissue Morphogenesis results from..... – Direction and number of cell divisions – Cell shape changes – Cell movement – Cell growth – Cell death – Changes in the composition of the cell membrane or secreted products – Cell differentiation is an obvious omission!
Important Term: Mesenchymal to Epithelial Transition
Fate Maps: Mapping the Movements of Cells in the Embryo The idea is to.... 1.Pick a developmental stage and a group of cells in the embryo that you want to study 2.Find a way to visually distinguish those cells from all of the rest 3.Find your cells again during and at the end of the stage and make a map of their fate
Figure 1.11 Fate maps of vertebrates at the early gastrula stage The value of fate mapping is clear from this figure, which shows the common organization of embryos even when the shapes differ.
1.Direct observation of pigmented cells in the embryo 2.Marking small groups of cells in the early embryo with dyes 3.Replacing embryonic cells of one species with those of another that look different 4.Replacing embryonic cells with those from the same species carrying transgenes The process has gotten more sophisticated as our tools have gotten better and better.
Direct observation of pigmented cells in the embryo (sea urchin larva)
Vital dye staining of amphibian embryos The first experimental fate maps allowed investigators to put color wherever and wherever needed.
Fate mapping using a fluorescent dye Powerful fluorescent dyes allowed investigators to take their fate map studies much later into development of the embryo.
Genetic markers as cell lineage tracers Chick and quail are so similar that they won’t immunologically reject the others’ cells plus quail have very large nucleoli and the cells are easy to distinguish from chick cells.
Figure 1.16 Chick resulting from transplantation of a trunk neural crest region from an embryo of a pigmented strain of chickens into the same region of an embryo of an unpigmented strain Chick and quail can also grow up with each other’s parts! Permanent fate maps!
Fate mapping with transgenic DNA shows that the neural crest is critical in making the bones of the frog jaw Now we can fate map nearly any embryo, at nearly any cell or stage, with molecular tools.
Evolutionary Developmental Biology (EvoDevo) Similarities and Differences Between Embryos Can Define Most Taxonomic and Evolutionary Relationships This idea pre-dates Darwin A center pin of “Origin of the Species” Two things show in the embryo: – Commonalities show common ancestry – Modifications show adaptations to environments Combined with von Baer: – Evolutionary modifications of related species should come later in development than those of distant species
Homology vs. Analogy Homologous structures arise from a common ancestral structure Analogous structures share a common function that has arisen independently in the two (or more) organisms
Larval stages reveal the common ancestry of two crustacean arthropods
Homologies of structure among human arm, seal forelimb, bird wing, and bat wing
How does developmental biology contribute to this evolution? Mice, humans and bats all start with two forelimb bones and five digits with webbing in between Bat wing has more rapid growth rate in finger cartilage making digits longer Bat wing also has a block to cell death in the webbing making them connected
Selectable variation through mutations of genes active during development
How does developmental biology contribute to this evolution? Humans bred the dachsund to go into badger dens during the hunt Unknowingly, we selected for an extra copy of fibroblast growth factor 4 (Fgf4) Fgf4 tells leg cartilage to stop growing and differentiate into bone An independently acquired mutation, a truncated Fgf5 gene, allows overgrowth of the hair shaft in long-haired dachsunds
Between 2% and 5% of humans are born with visible developmental abnormalities some are caused by mutations some are caused by environmental disruptions of development These abnormalities have provided a great deal of insight into normal development How can these developmental relationships directly affect us?
Single gene mutation Piebald Syndrome: KIT mutation reduces cell division in neural crest cells. These cells give rise to pigment cells, ear cells, gut neurons, blood cells and germ cells. Human syndromeMouse model