Talk:K12 Limbs

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9 The timing of gene expression is important in the developmental process

9.1 Identify the role of genes in embryonic development

9.2 Summarise the role of gene cascades in determining limb formation in birds and mammals.

9.3 Describe the evidence which indicates the presence of ancestral vertebrate gene homologues in lower animal classes

9.4 Discuss the evidence available from current research about the evolution of genes and their actions

9.5 Identify data sources, gather, process and analyse information from secondary sources and use available evidence to assess the evidence that analysis of genes provides for evolutionary relationships


Axis Proximodistal Dorsoventral Anteroposterior
Limb Structure shoulder to fingers, hip to toes back and front of the limb order of digits
Gene Wnt7a growth factor then secretes other growth factors (FGF2, 4, 8) Wnt7a growth factor Sonic hedgehog (SHH)
Where tip of the limb Apical Ectodermal Ridge (AER) back of the limb mesenchyme Zone of Polarizing Activity (ZPA)
Expression Example
(mouse)
Limb patterning factors 04.jpg Limb patterning factors 01.jpg Limb patterning factors 03.jpg