Bart - Metamorphosis Hormones Flashcards
What hormone primarily drives amphibian metamorphosis?
Thyroid hormones, particularly thyroxine (T4) and tri-iodothyronine (T3).
How is Thyroxine (T4) converted into its more active form?
T4 is converted into T3 by the enzyme Type II deiodinase (D2).
What are the four principle responses of tissues to thyroid hormones during metamorphosis?
Growth, apoptosis, remodeling, and respecification.
What is the role of Type II deiodinase (D2) in thyroid hormone activity?
Type II deiodinase (D2) converts T4 into the more active T3.
What is the significance of TRβ in metamorphic climax?
TRβ amplifies the metamorphic response and accelerates metamorphosis through a positive feed-
forward loop.
What role does prolactin play in amphibian metamorphosis?
Prolactin delays metamorphosis by counteracting the effects of thyroid hormones.
Explain the role of ephrin B in eye migration during metamorphosis.
Ephrin B guides certain neurons to project ipsilaterally, aiding in the development of binocular vision.
What happens to TR-RXR dimers when T3 binds to them?
When T3 binds to TR-RXR dimers, they convert from repressors to activators, initiating gene expression.
How does T3 influence the growth of neurons in the frogs limbs?
T3 induces the growth of new neurons that extend axons to the developing limb muscles.
What effect does blocking T3 have on limb development in frogs?
Blocking T3 prevents proper neuronal development, leading to paralysis of the limbs.
