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Molecular and Organismal Development. Chapter 21: pp 411-429 Chapter 47: pp 992-1008. Topics in Development. 1 . totipotency : development depends on selective expression of the whole genome present in every cell.
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Molecular and Organismal Development Chapter 21: pp 411-429 Chapter 47: pp 992-1008
Topics in Development • 1. totipotency: development depends on selective expression of the whole genome present in every cell. • 2. blastula to gastrula: comparative analysis yields insights into the general nature of development • 3. the three fundamental processes: • cell division (differential rates of division are critical, programmed cell death is significant) • cell differentiation (changes in integration and shape are critical; targeting cells with signals is a critical part of the process) • morphogenesis of tissues and organs (includes defining the individual’s polarities, dividing the organism into segments, and – in animals -- migration of cells in tissue origin)
Figure 21.2 Some key stages of development in animals and plants
Topics in Development • 1. totipotency: development depends on selective expression of the whole genome present in every cell. • 2. blastula to gastrula: comparative analysis yields insights into the general nature of development • 3. the three fundamental processes: • cell division (differential rates of division are critical, programmed cell death is significant) • cell differentiation (changes in integration and shape are critical; targeting cells with signals is a critical part of the process) • morphogenesis of tissues and organs (includes defining the individual’s polarities, dividing the organism into segments, and – in animals -- migration of cells in tissue origin)
Figure 47.12 Cleavage, gastrulation, and early organogenesis in a chick embryo
The cells in the three germ layers have defined fates in the adult:
Topics in Development • 1. totipotency: development depends on selective expression of the whole genome present in every cell. • 2. blastula to gastrula: comparative analysis yields insights into the general nature of development • 3. the three fundamental processes: • cell division (differential rates of division are critical, programmed cell death is significant) • cell differentiation (changes in integration and shape are critical; targeting cells with signals is a critical part of the process) • morphogenesis of tissues and organs (includes defining the individual’s polarities, dividing the organism into segments, and – in animals -- migration of cells in tissue origin)
Topics in Development • Homeotic genes a. the determination of appendage identity on fruitfly segments b. the evolution of form in segmented animals • Morphogenesis in Plants • Organ identity genes in flower development
Figure 21.11 Key developmental events in the life cycle of Drosophila
Figure 21.12 The effect of the bicoid gene, a maternal effect (egg-polarity) gene Drosophila
Figure 21.13 Homeotic mutations and abnormal pattern formation in Drosophila
Homeotic genes:the DNA sequence of the gene (blue) contains a 180 bp sequence—the homeobox—(red) that is highly conserved. The homeodomain - 60 amino acids of the homeotic gene product that remain very similar in all proteins made by homeotic genes.
Figure 17.7 The initiation of transcription at a eukaryotic promoter
control of transcription in C.elegans lin-3 | tctctccctattcaatgcacctgtgtattttatgctggttttttcttgtgaccctgaaaactgtacacacaggtgttcttaccaatgtctcaggcatttttggaaaagtaatattaagaaaattatacatattttcttgaatacgaaaaatttaaATGTTCGGTAAATCGATTCCTGAACGACTTCTAGTCGCATTT HLH-2 binding site NHR binding site EXON is in uppercase letters.
Figure 19.10 Three of the major types of DNA-binding domains in transcription factors
The homeobox is relatively constant because it has a precise job.
The homeobox is relatively constant because it has a precise job.
Figure 21.14 Homologous genes that affect pattern formation in a fruit fly and a mouse
Topics in Development • Homeotic genes a. the determination of appendage identity on fruitfly segments b. the evolution of form in segmented animals • Morphogenesis in Plants • Organ identity genes in flower development
CRUSTACEANS COMPARED: EVOLUTIONARY TRANSFORMATION ROCK CRAB LOBSTER
Figure 32.8 Animal phylogeny based on sequencing of SSU-rRNA lophophore
Figure 32.13 A sample of some of the animals that evolved during the Cambrian explosion
Porifera and Cnidaria are prominent in the Burgess Shale Annelid worms in the Burgess shale
Anomalocaris hunts so are arthropods!!
Figure 26.8 The Cambrian radiation of animals Causes of the radiation: Atmospheric oxygen reaches sufficient levels. Predator-prey relationships originate. Homeobox genes evolve. D R D PL P 525 PL PL Burgess Shale PE (Ediacaran)
Evolutionary changes in the timing of homeobox genes yield morphological change. Artemia, the brine shrimp
Another representation of the sequence of homeotic gene expression in an arthropod. Notice the continued prominence of Antp, Ubx, and Abd paralogs.
Timing of expression of the homeobox genes Antp, Ubx, and AbdA. Fading lines indicate weaker expression later in development.
Number of homeobox paralogs increases in arthropods. This illustration also shows change in timing of gene expression.