A.1 Neural Development

Understandings: The neural tube of embryonic chordates is formed by in-folding of ectoderm followed by elongation of the tube. Neurons are initially produced by differentiation in the neural tube Immature neurons migrate to a final location An axon grows from each immature neuron in response to chemical stimuli Some axons extend beyond the neural tube to reach other parts of the body A developing neuron forms multiple synapses Synapses that are nut used do not persist Neural pruning involves the loss of unused neurons The plasticity of the nervous system allows it to change Application Incomplete closure of the embryonic neural tube can cause spina bifida Events such as strokes may promote reorganization of brain function Skill Annotation of a diagram of embryonic tissues of Xenopus, used as an animal model, during neurulation

Xenopus – frog embryonic tissue

Field of Study Characteristics needed for model Suitable species Genetics Large numbers and short generation times Fruit fly Baker’s yeast Nematode worm Developmental Biology Robust embryos that are easily manipulated Chicken African clawed frog (Xenopus) Genomic studies, such as genes that cause diseases 60% of human genetic diseases studied have a counterpart in the fruit fly and nematode Nematode Comparative genomics The mouse genome is similarly organized to the human genome Mouse