BIO153H5 Lecture Notes - Lecture 2: Tiger Salamander, Limb Development
Biology Lecture 2.1
What triggers new species?
• Changes in Rate & Timing of gene expression
o Heterochrony and the role of paedomorphism
Paedamorphosis: Sexually maturing early
• Tiger salamander: metamorohases from larva= adult reproduces
• Breeding for particular appearance
o Initial reason was to achieve certain traits. Eg: bulldogs were bread to have
stronger jaws, short flat face.
o All mammalian animals adapt fast growth.
o Peramorphasis: physically maturing early
▪ Cope’s Rule: overall increase in size
• Body size and speciation
o body size usually increases from early to later forms in a lineage
• Hox genes: (regulatory & evolutionary role)
o The hox genes tell the dna how to sequence the change
o Nausea in pregnant women: it controlled the nausea, but it interfered with the
proteins responsible for the limb development.
Recognised that regulatory genes were responsible for such problems.
• Hox Genes are arranged in segments where the first one is the original, and the rest
ones are just the replicate of it.
NOTES
Plants have a genetic material called MADS which are specific hox genes
find more resources at oneclass.com
find more resources at oneclass.com
