Midterm 3 April 12, 2004
1. The notochord _________________ the neural tube.
a) evolved into
b) induces D-V pattern in
c) develops into
d) is derived from
2. Chick and mouse have identical numbers of vertebrae but the relative numbers of cervical and thoracic vertebrae are different. This is thought to result from
a) alternative guidance cues for neural crest cells
b) baby chicks having to stretch their necks for food
c) different numbers of Hom-C gene complexes
d) different patterns of Hox gene expression
e) different gradients of bicoid protein
3. Neural crest cells
a) form at the dorsal side of the neural tube
b) migrate extensively
c) give rise to sensory ganglia, teeth, pigment cells of the epidermis, connective tissues of the skeleton and heart and epinephrine producing cells of the adrenal gland
d) all of the above
e) none of the above
4. Neurotropins are
a) neuronal chemotactic factors secreted by target cells
b) neuronal precursor cells
c) molecules of the extracellular matrix that guide neurons
d) molecules that induce neuronal cell fate through lateral specification
e) pharmacological agents that induce nerve regeneration
5. Which of the following is NOT derived from mesoderm?
e) Neural tube
6. (20 points) Breifly describe the outcome of each of the following experiments on vertebrate limb development:
a) Hindlimb mesenchyme is combined with forelimb ectoderm.
b) The anterior region of the limb field is treated with Sonic hedgehog (Shh).
c) The progress zone from an early stage limb bud is transplanted to a late stage limb bud.
d) FGF is used to induce the formation of a limb at the boundary between the TBX4 and TBX5 expression domains.
e) A second apical ectodermal ridge (AER) is grafted onto a limb bud.
7. (10 points) Pollen self–incompatibility is controlled by the S-locus, a complex locus encoding several genes. These genes include two encoding a receptor-kinase and its ligand. Describe how these function in the cell recognition between the pollen and receptive surface of the flower.
8. (10 points) a) Describe one line of experimental evidence which demonstrates that testosterone is responsible for the difference between male and female mammary development.
b) Describe the experimental evidence which shows that the mesenchyme, and not the epithelium, is the target of testosterone action.
9. (10 points) Amphibian metamorphosis is controlled by the thyroid hormones T3 and T4.
a) Describe what happens during frog metamorphosis if a premetamorphic eye is transplanted onto the tail of a tadpole.
b) What general principle of the hormonal control of metamorphosis does this illustrate?
10. (10 points) We all know that bones are capable of healing.
a) Describe the outcome of the experiment we covered in class where sections of bone were removed from two dog legs; one was treated with parathyroid hormone, the other not.
b) What is the medical significance of this result?
11. (15 points) The diagram at the right depicts two reproductive meristems of Arabidopsis. In a wild type plant, meristem 1 represents an inflorescence meristem and meristem 2 represents a flower meristem.
a) Where would the TERMINAL FLOWER (TFL) gene be expressed in a wild type plant?
b) In a leafy (lfy) loss of function mutant, what would be the identities of each meristem?
c) In a lfy loss of function mutant, where would TFL be expressed?
d) In a transgenic line constitutively overexpressing LFY (e.g. 35S-LFY), what would be the identities of meristems 1 and 2.
e) In a transgenic line constitutively overexpressing LFY (e.g. 35S-LFY), where would TFL be expressed?
12. 10 points) Describe how the CLAVATA (CLV) signaling system and the WUS gene function in the shoot apical meristem to maintain the proper amount of stem cell proliferation. I.E. How is the balance between the activities of the central zone and organizing center maintained? Draw a diagram if necessary.