Typed class notes covering lecture 3 in the Development Biology course (code BioD104) at University of California, Irvine. Made by a biology student taking said course over a summer session. Document comes with color-coded notes and textbook diagrams.
Lecture 3 Abbreviation Key:
Thursday, August 8, 2019 7:54 PM b/c = because
b/w = between
w/ = with
expt = experiment
• Pair-rule genes (PR): expressed in 7 transverse stripes that correspond to alternate PS. ex. = example
○ Gap genes regulate para-rule gene expression. But…
○ How do genes expressed in broad expression domains give rise to a repeated series of stripes?
• Eve-skipped (eve): defines the odd PS.
○ Used to study the regulation of PR genes by gap genes.
○ Adjacent enhancers control eve's gene expression.
○ "The eve promoter contains independent regulatory modules for independent stripes." ->
Enhancer modules give rise to individual stripes along the eve expression pattern.
○ Gap gene proteins bind to the regulatory region of eve-skipped promoters. -> Activate/repress eve.
• Experiment: known genes upstream of each eve stripe were dyed blue. Forms stripes along embryo.
• -> Enhancers can regulate spatial expression.
• Stripe 2 element controls PS #3. From the graph, we know that…
○ Eve is activated by LOW Bicoid and HIGH hb.
○ Giant represses eve to form an anterior border.
○ Kruppel represses eve to form a posterior border.
• Enhancers control which TFs can bind to the DNA. -> Different TFs on A/P axis expressing certain gap
genes.
• Segment polarity (SP) genes
• SP genes act after cellularization.
• Expressed in 14 stripes, regulated by combo of PR genes.
• Some SP genes encode secreted protein. (Wingless)
• SP mutant genes -> tandem/mirror image duplications of A or P part of each segment.
○ WT: A segment is hairy, P segment is not/naked.
○ MT: A next to A, P next to P…
○ CONCLUSION: mutations effect polarity within each segment!
• Hierarchy of genes: maternal genes dictate zygotic genes -> Gap genes -> PR genes -> Segment
polarity genes -> Selector genes -> Homeobox? genes
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