Lecture 4

Question 1

An important system responsible for the shape of the head was what?

Answer 1

olfactory system

Question 2

Cranial structures originate from….

Answer 2

mesoderm and/or neural crest cells

Question 3

what is the gene that induces neural crest migration?

Answer 3

FoxD

Question 4

what gene is tunicates lacking that may answer why they do not have a cranium?

Answer 4

twist gene

Question 5

splanchnocranium structures are derived from what?

Answer 5

neural crest cells

Question 6

the nasohypophyseal duct plays a key role in the development of the cranial structure because….

Answer 6

because it is in the way of expanding the neural crest contribution from the mandibular arch. So for animals that have this like lamprey and hagfish, the will not be able to develop facial series, mandibular series, temporal series etc.

Question 7

the lack of what gene set the stage for the evolution of jaws?

Answer 7

Hox

Question 8

define heterotropy:

Answer 8

when a structure changes its location in the body.

Question 9

In gnathostomes, what novel gene is present that helps pattern the joint that patterns the jaw and moves the location of the POC. This is not seen in lamprey.

Answer 9

Bapx

Question 10

The position of Hyoid Arch (Pharangeal Arch #2) is determined by the expression of what gene?

Answer 10

Hox

Question 11

Consequences of a posterior shift in the location of some oronasal structures in gnathostomes include—

Answer 11

• acquisition of paired nasal openings (diplorhiny)
• hypophyseal opening moves rearward & inward
• adenohypophysis from Rathke’s pouch in roof of mouth
• is room for forebrain to expand rostrally

Question 12

What are some of the major changes in regards to jaws and arches that occur in vertebrates?

Answer 12

Upper jaw attached directly to brain case
Posterior arches: become glossal skeleton
• support trachea
• support tongue (lingual feeding)
• most bones are lost