The zootype and the phylotypic stage

Article Abstract:

The animal kingdom may be given a morphological definition using the concepts of zootype and phylotypic stage. An animal is an organism displaying a particular spatial pattern of gene expression. This pattern is defined as the zootype. The zootype is most clearly expressed at the phylotypic stage of embryonic development. The phylotypic developmental stage has several definitions including that stage at which all major body parts are represented in their final relative positions as clusters of undifferentiated cells.

Column, Genetic aspects, Phylogeny, Zoology, Morphology (Animals), Animal morphology

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High hops of transgenic frogs

Article Abstract:

The technique of transgenesis or the introduction of engineered genes into the organism can be applied to frogs to gain information on animal development. The introduction of the transgene into the sperm instead of tissue culture cells avoids the problem of aneuploidy in Xenopus. The technique enables the conduction of overexpression experiments on embryos. Genes can be turned on or off of any gene at any developmental or positional stage in the embryo.

Methods, Observations, Genetically modified animals, Animal genetic engineering

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Growth factor lends a hand

Article Abstract:

Studies on the molecular basis of limb formation in amphibians show that implanting heparin-acrylic leads soaked in fibroblast growth factor (FGF) could induce extra limbs from the flank of the chick embryo. These limb buds possess an apical ectodermal ridge and show typical expression of the genes Sonic hedgehog and hoxd13. These FGF bead inductions have contributed to the understanding of limb formation and development in embryos.

Physiological aspects, Growth factors, Amphibians, Extremities (Anatomy), Animal anatomy

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