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How do animals control development?
Transcription activation of gene combinations in different cells
Activating combinations of genes in patterns controls development decisions (tissue type, cell type, cell life)
Baer and Haeckel
Observed that embryonic stages of different vertebrates resembled each other
Ontogeny recapitulates phylogeny
Fruit fly life cycle
Fertilized egg > blastoderm > embryo > larva > pupo > adult fly
Mutation in HOX gene in fruit flies
Recessive mutation in HOX gene UBX
: 2 winged > 4 winged
Dominant mutation in HOX gene Antp
: turned antennae into legs
Southern Blot
Method for finding whether genes from one species are present in the genomes of other species
Have a gel where the entire genomic DNA is cut with restriction enzymes so you get a range of different fragments
Put gel on filter paper with salt and water -> DNA sticks to filter paper
Take filter and put in solution with purified probes and wash of probes that are not bound
Expose to x-ray film -> have bands that show you similar genes
Evidence the mammals have HOX genes similar to flies
"Zoo" southern blot
Mutation of mouse Hox10a,b,c
Result in extra ribs in the body
Evidence the fruit flies and mammals had a common ancester
Conservation of Hox gene clusters
Changes in localized patterns of Hox gene expression patterns are correlated with changes in animal morphology during evolution
What controls the developmental patterning of limbs?
Posterior hox genes
Overlapping HOX gene expression
"A" cluster - activated in different zones of the limb bud proximal-distal axis
"D" cluster - activated in different zones of the limb bud anterior-posterior axis
Synpolydactyly Syndrome
Either heterozygous or homozygous for a HoxD13 gene that has an expansion of Alanine codons
Fewer or more fingers and toes
Hand-foot-genital syndrome
Have a stop codon in place of Tryptophan codon
Sequence of HoxA13 gene
Other homebox gene families
Engrailed
Tinman
D11
POU
Paired
Eyeless
Exd/Pbx
Homeobox gene that controls heart development
Nikx2.5 (fetal) - abnormal heart morphogenesis
Tinman (fly embryo) - loss of dorsal vessel and visceral mesoderm
Homeobox gene that control eye development
Pax6 (fetal) - Aniridia in humans and small eye in mice
Eyeless (fly) - almost lasck all eyes
Author
LT24
ID
5384
Card Set
Model organisms
Description
Hox
Updated
2010-01-28T23:01:11Z
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