Amphibian Gastrulation And Primary Embryonic Induction Flashcards
See page 92!
…
Explain what the Distal-less (DII) gene is responsible for in drosophila larvae and where it is expressed/ inhibited
In drosophila Distal-less (DII) gene is critical for forming proximal-distal axis of appendages (drosophila larvae do not have any appendages themselves).
Expressed in head and thorax, inhibited by Abd-A and Ubx in abdomen-linked yo presence of appendages (none in abdomen)
Unlike Drosophila butterfly larvae have prolegs on their abdomen. Why is this?
Abd-A, Ubx and DII expression (identical in drosophila but in butterflies in some regions these are not being switched on) similar between Drosophila and butterfly early in development, but Abd-Ab and Ubx expression is later in development, but Abd-A and Ubx expression is later inhibited in patches of the abdomen in buttery only- allowing expression of DII and development of prolegs
Ultrabithorax (Ubx) is expressed throughout the imaginal discs in which segment?
The third thoracic segment
Butterflies have hindwings however flies have what?
Halteres
What is the difference in general pattern of Hox gene expression in flies and butterflies?
There is no difference
See middle page 93. Sentence beginning many of the genes…
…
In vertebrates which side of the animal does the central nervous system run down?
The dorsal side
What gives rise to internal organs In gastrulation in amphibians?
Future Endodermal and mesodermal cells move from the outer surface of the embryo to the inside, where they give rise to internal organs
Where do the future mesoderm and ectoderm lie?
In the marginal zone immediately below the animal pole
Give an overview at gastrulation
. Begins with bottle cells forming in the blastopore region followed by involutuon if mesoderm at dorsal lip and under the ectoderm
. Marginal zone endoderm moves onwards under the mesoderm, forming roof of anchenton
. Ectoderm cells spread out (epiboly), from animal pole, eventually covering embryo
. Mesoderm cells move under ectoderm (convergent extension)
. Tissue movements create a new body cavity, the archenteron, which will become the gut
. The blastocoel reduces in size and blastopore surrounds a yolk plug
. (The cells in the vegetal poles of amphibians are larger than in the animal pole because they have more yolk in them)
. (The bottle cells move onwards and start forming the tube that will later form into the gut but this occurs in one of the lateral sides of the embryo, so it actually occurs at the side of the embryo forming the dorsal lip- and what starts to happen is that these cells will start to thicken and move onwards and you get a tube surrounded by ectoderm that moves up this side and moves into the top of the embryo forming the gut. The cells that form the mesoderm they also move onwards and follow the extension of the developing ectoderm cells and become parallel to the ectoderm, forming a sort of sandwich look and they actually move inside that whole the is formed by the dorsal lip. This forms a displacement and shiftsbthe blastocoel to the side, so the gut forms here
What does the archenteron become in gastrulation?
The gut
How is the roof of the archenteron formed?
Marginal cone endoderm moves inwards under the mesoderm
How does gastrulation begin?
With bottle cells forming in the blastopore region followed by involution of mesoderm at dorsal lip and under the ectoderm
What are the cells in vegetal poles of amphibians larger than in the animal pole?
Because they have more yolk in them
In neurulation what does the midline notochord form?
The vertebral column
In neurulation what does the dorsal-lateral the somites form?
Vertebrae, ribs, muscle and skin
What are cells that overlie the mesoderm cells destined to become?
The nervous tissues of the brain and spinal cord (the neurectoderm)
What is the tissue of the brain and spinal cord called?
Neurectoderm
What is the inner lining of the gut formed by?
The ectoderm
What does the mesoderm go on to form?
The notochord- which will later turn into the vertical column running down the dorsal surface of the animal
Ectoderm cells roll up and form a tube which is? What is this called?
The spinal cord and in the anterior the brain- neurolation
How is the neural tube formed?
. Inwardly migrating cells form the roof of the archenteron
. These cells will form the dorsal mesoderm:
- in the midline notochord
- dorso-lateral the s’mores. Cells that overlie these mesoderm cells are destined to form the nervous tissue of he brain and spinal cord
. The neuroectoderm
. First they form the neural plate
. Then the plate forms a neural groove
. And finally a neural tube
The role of the underlying mesoderm in specifying the fate of the overlying ectoderm was discovered early in the 20th century by the embryologist Hans Spermann and his collaborators. What was this proceeds termed?
Primary embryonic induction
