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Gene Control in Development

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1 Gene Control in Development
Lecture 10 Gene Control in Development Cell type specification Development of an organism Reading: Chapter 11:471-2 Chapter 15.1; 15.3; 15.4 Chapter 22.2 Molecular Biology syllabus web site

2 Cell type specification in the yeast model system





7 Different mating types express specific transcription factors that form complexes with MCM1
MCM1 is a general transcription factor found in all cell types




11 Transcription factors and lessons from yeast
Factors may act alone or in combinations The same factor in different combinations may contribute to complexes that act as repressors or activators.

12 Cell type specification in animals

13 Cell type specification in mammals: skeletal myogenesis proceeds through three stages

14 How to identify factors involved in muscle development?
To identify transcription factors that may play a role in “determination” of cells destined for a specific organ: Isolation of cDNAs by subtractive hybridization (fibroblasts vs. myoblasts) Testing by transformation of undetermined cell types to demonstrate effect on “determination” Create “Knockouts” to confirm information on the stage at which a specific factor acts Characterization: function as heterodimers (key to specificity is the interaction with other factors) and belong to family of basic helix-loop-helix DNA binding transcription factors (bHLH) MRFs, muscle regulatory factors binding to “E” box in many genes

15 Microarray analysis shows global patterns of gene expression during differentiation

16 Development of an organism: Drosophila melanogaster

17 Drosophila has two life forms

18 Patterning information is generated during oogenesis and early embryogenesis

19 Formation of the blastula during Drosophila early embryogenesis

20 Four maternal gene systems (anterior, posterior, terminal, dorsoventral) control early patterning in fly embryos

21 Mechanisms controlling pattern formation

22 Morphogens regulate development as a function of their concentration: maternal bicoid gene specifies anterior region in Drosophila Red: hunchback Green: Krupple Yellow: even-skipped Orange: fushi tarazu

23 Maternally derived inhibitors of translation contribute to early Drosophila patterning

24 Nanos regulates the translation of Hunchback and helps to establish the Hunchback gradient

25 Use of mutants to characterize Nanos as a translational inhibitor

26 HOX genes and transcription factors discovered through “homeotic mutants” showing transformation of one body part into another

27 Expression domains of Hox genes in Drosophila and mouse embryos

28 Specification of floral-organ identity in Arabidopsis: flowers contain four different organs

29 Three classes of genes control floral-organ identity

30 Expression patterns of floral organ-identity genes

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