Early Development and Axis Formation in Amphibians

Question 1

The next phase of gastrulation involves the _ of the marginal zone cells while the animal cells undergo _ and converge at the blastopore.

Answer 1

Marginal zone cells - involution
animal cells - epiboly

Question 2

When the migrating marginal cells reach the _ of the blastopore, they turn inward and travel along the inner surface of the outer hemisphere cells.

Answer 2

dorsal lip

Question 3

The first cells to compose the dosal blastopore lip

Answer 3

bottle cells

Question 4

bottle cells that first compose the dorsal blastopore lip becomes the

Answer 4

pharyngeal cells of the foregut

Question 5

precursor of the head mesoderm

Answer 5

prechordal plate

Question 6

What is the sequence of cells in dorsal blastopore lip?

Answer 6

bottle cells - pharyngeal cells of foregut
prechordal plate
chordamesoderm - notochord

Question 7

transient mesodermal backbone that plays an important role in distinguishing and patterning the nervous system

Answer 7

notochord

Question 8

The remaining patch of endoderm is called _ and is eventually internalized.

Answer 8

yolk plug

Question 9

midblastula transition

Answer 9

preparing for gastrulation

Question 10

What is the first precondition for gastrulation?

Answer 10

activation of the genome

Question 11

In Xenopus, the nuclear genes are not transcribed until late in the _

Answer 11

Twelfth cell cycle

Question 12

Who said that nuclear genes is not transcribed until late in the twelfth cell cycle?

Answer 12

Newport and Kirschner

Question 13

different genes begin to be transcribed in different cells, and blastomeres acquire the capacity to become motile

Answer 13

Midblastula transition

Question 14

different transcription factors becomes active in different cells at this time

Answer 14

midblastula transition

Question 15

critical in determining the location of the blastopore as is the point of sperm entry

Answer 15

vegetal cells

Question 16

direct cytoplasmic movements that empower the vegetal cells opposite the point of sperm entry to induce the blastopore in the mesoderm above them

Answer 16

microtubules of the sperm

Question 17

unfertilized egg was radially symmetrical about the animal-vegetal axis, while the fertilized egg now has a

Answer 17

dorsal-ventral axis (bilaterally symmetrical)

Question 18

shown that the cytoplasm of the presumptive dorsal cells differs from that of presumptive ventral cells

Answer 18

Fluorescence microscopy of early embryos

Question 19

The side where the sperm enters marks the

Answer 19

future ventral surface of the embryo

Question 20

The opposite side of sperm entry where gastrulation is initiated

Answer 20

future dorsum of the embryo

Question 21

If cortical reaction is blocked, there is _, and embryo dies as a mass of ventral cells

Answer 21

no dorsal development

Question 22

Although the sperm is not needed to induce these movements in the egg cytoplasm, it is important in determining the _

Answer 22

direction of the rotation

Question 23

when a xenopus egg is turned 90 degrees, so that the point of sperm entry faces upward, the cytoplasm rotates such that the embryo initiates gastrulation on the _ as sperm entry.

Answer 23

same side (gerhart and cooke)

Question 24

hypothesized that the twinning was caused by the formation of two areas of interaction

Answer 24

Black and Gerhart

Question 25

Amphibian gastrulation is first visible when a group of marginal endorderm cells on the dorsal surface of the blastula sinks into the embryo. The _ surface of these cells contracts dramatically, while the _ ends expand.

Answer 25

outer - dramatically
inner - expand

Question 26

found that bottle cells from early salamander gastrulae could attach to glass coverslips and lead the movement of those cells attached to them

Answer 26

Johannes Holtfretter