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Modified over 5 years ago
I can’t wait to grow up!
The fruit fly body plan is self-assembled in 24 hours
How is the body plan specified? Egg ---> animal in 24 hours!
Eric Wieschaus and Christiane Nüsslein-Volhard used genetics to identify proteins that set up the embryonic body plan
The molecular genetics of pattern formation in candy corn The wild-type pattern Anterior Posterior
We collected a series of mutants affecting the body plan Wild-type Anterior group Gap gene Posterior group Morphogenesis defects
The wild-type body is segmented and each segment has a unique identity and thus produces distinctive structures
Wieschaus and Nüsslein-Volhard removed single genes and looked for effects on the body plan
Wildtype larva bicoid mutant bicoid mutants have no head!! Gilbert Fig. 9.13
Remember that cleavage starts without cell division in Drosophila
= bicoid mRNA= nanos mRNA
Increasing Bicoid concentration Head Tail Bicoid accumulates in a gradient
A gradient of the bicoid transcription factor turns on different genes at different "thresholds"
These “bicoid target genes” are known as the gap genes Hunchback Kruppel Knirps Expression pattern of proteins ecoded by gap genes
Gap gene mutants are missing different regions of the body
Wildtype Krüppelhunchback knirps
Alberts Chapter 8 title page
So, in summary so far… Maternal Determinants Zygotic Gap Genes Zygotic Pair-rule Genes
Figure 9.8(1) Model of Drosophila Anterior-Posterior Pattern Formation
Isn’t life wonderful, beautiful and incredible!
Ed Lewis was far ahead of his time
Wildtype Antennapedia mutant
Wildtype Ubx mutant T2 A2 T3 and A1 take on a 2nd thoracic identity T2
Wildtype Ubx abdA AbdB triple mutant T2 T3 A1 A8 T2 All segments take on a 2nd thoracic identity
Is Ubx is expressed at the right time and place to make in T3 different from T2? Yes! Ubx is expressed in T3 and A1
Figure 9.28 Homeotic Gene Expression in Drosophila
Ultrabithorax, abdA, and AbdB normally repress expression of the“leg gene” Distalless in the abdominal segments Distalless in wild-typeDistalless in triple mutant T1 T2 T3 abdomen
Lewis hypothesized that the duplication and diversification of homeotic master regulators underlies the evolution of an increasingly complex body plan
The human body is also built up from reiterated units with different identities along the A/P axis
As we’ll see later, mammals also have homeotic genes expressed at different places along the A/P axis
DELTA mutant cells can be rescued by wild type neighbors. Therefore, DELTA must be the SIGNAL. NOTCH mutant cells cannot be rescued by wild type neighbors. Therefore, NOTCH must be the Receptor.
Homeobox Genes Body organisation.
1 * egg: generate the system * larva: eat and grow
Drosophila melanogaster 2.5mm Movie. The Life Cycle 1-2 weeks 36hr 60 hr 12 hr.
Studying Segmentation Mutants in Balanced Stocks.
Pattern formation in drosophila Katja Nowick TFome and Transcriptome Evolution
12 The Genetic Control of Development. Gene Regulation in Development Key process in development is pattern formation = emergence of spatially organized.
Chapter 16 The Genetic Basis of Development. Determination is a multistep process Pluripotent embryonic cells MesodermEctoderm Nerve cells Skin cells.
Lecture 6 Anterior posterior axis formation-the posterior signal Anterior posterior axis formation-down the hierarchy.
9.17 Generalized model of Drosophila anterior-posterior pattern formation (Part 1)
Axis Specification I.
MiRNA miRNA ancient form of regulation. Protection against viral pathogens Quick regulation and turnover of mRNA.
Differential Gene Expression
Embryonic Development & Cell Differentiation. During embryonic development, a fertilized egg gives rise to many different cell types Cell types are organized.
Anterior-posterior patterning in Drosophila
Gradients, cascades, and signaling pathways
Flies are quick!. The fly body plan: each segment has a unique identity and produces distinctive structures 3 head 3 thorax 8 abdomen.
6 and 8 November, 2006 Chapter 18 Gene Regulation During Development.
Drosophila homeotic mutants
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