Cellular Mechanisms of Development Chapter 19

Developement Growth (cell division) Differentiation Pattern Formation Morphogenesis

Cell Division CDK’s control Cell cycle Cleavage –Blastomeres –No G Phase in early cell division

C.elegans

Stem Cells Tissue specific Stem cells Totipotent Plouripotent

Blastocyst Embryonic Stem Cells

Do plants have Stem Cells?

Cell Differentiation First Cell Determination Occurs –Humans have 210 types of cells Proteins, morphologies, and functions help us tell them apart

How can we tell if something is Determined? Do an experiment –Transplant cells and see what they become –Figure 19.5

Molecular Basis of Determination Use transcription factors to change patterns of gene expression. Cells become committed to a particular developmental pathway in two ways- –Cytoplasmic determinants from the parents –Cell-cell interactions

Induction Animal and Vegetal pole interactions Fibroblast growth Factor (FGF)

Reversal of Determination Experiments showed that single cells from fully differentiated plants could develop into mature plants What about animals? –Frog Experiments –Mammals

Dolly

Steps to cloning Dolly 1. Cell containing source DNA was grown on a medium to stop the cell cycle 2. Eggs obtained from the ewe were enucleated 3.Somatic Cell Nuclear transfer (SCNT) 29 of 277 fused couplettes formed into embryos and were implanted into surrogate mother 1 lamb was born 5 months later

Problems with Reproductive Cloning Low Success Rates Large offspring Syndrome Develop age related disorders very early –Why Lack of Imprinting

Therapeutic Cloning

Stem Cell Research Debate What do you think?

The future of Stem Cells Adult stem cells may offer an alternative to ES cells

Body Axis

Pattern Formation Determines that is going to develop where Maternally Determined Prefertilization Postfertilization Syncytialblastoderm Cellular Blastoderm Segmented Embryo

Anterior-Posterior Axis Bicoid and Nanos protein gradients Hunchback and Caudal maternal messengers –Found evenly throughout the egg

Dorsal- Ventral Axis Gurken and Dorsal Proteins –Not what you would expect

Segmentation Genes Gap Genes- map out the most basic subdivisions of the embryo Pair-rule genes- subdivide the segments made by the gap genes ( ex hairy) Segment Polarity Genes- subdidived segments made by P-r genes (ex engrailed)

Homeotic Genes Give each segment an identity –Awesome mutations- Untrabithorax and Antennapedia

Homeotic Gene Complexes Bithroax Complex Antennapedia complex –HOX genes- refers to all homeobox containing genes that determine the identity of a body part –Order of homeobox gene corrosponds to body segment

Plants Do not have Hox genes have Mads-box gene

Morphogenesis Ordered form and structure Regulated in 5 ways –Number, timing, and orientation of cell divisions –Cell growth and expansion –Changes in cell shape –Cell migration –Cell death

Cell division and Unequal cytokinesis This allows cells to be different sizes

Cell death Apoptosis vs Necrosis When does apoptosis happen?

Cell Migration Does not happen in Plants Achieved by Cadherins and Integrins

Plants Plane of cell division determines morphogenesis –Smaller cell becomes embryo while larger becomes suspensor –Words to know for AP test Cotyledons and Apical Meristem

Environmental Effects Some Obvious –Jack Pines –Dormant Seeds Some not so Obvious –Thalidomide

TSD Why is this important? Why now more than in the past?

Endocrine Disrupters DDT DES

Tissue Development