6: Gastrulation and the Formation of the Primary Organ Rudiments

Question 1

germ layers are formed through cell
movements is called

Answer 1

gastrulation

Question 2

ectoderm forms

Answer 2

1. epidermis of the skin
2. epithelium of the oral and nasal cavities
3. nervous system
4. sense organs

Question 3

mesoderm forms

Answer 3

1. muscle and connective tissue: bone
2. components of circulatory
3. urinary
4. genital systems

Question 4

endoderm forms

Answer 4

1. mucosal epithelium
2. glands of respiratory
3. glands of digestive

Question 5

Gastrulation came from greek means

Answer 5

gastrula meaning “belly” or “little stomach”

Question 6

a diagram of an egg or blastula, indicating the fate of each cell or region, at a
later stage of development

Answer 6

Fate Maps

Question 7

analysis of the fate of each blastomere after first and second cleavage is
called

Answer 7

cytogeny or cell lineage study

Question 8

the first fate maps date back to the 1880s and in 1905 the first comprehensive
collection of Ascidian (sea squirt) fate maps was published by

Answer 8

Edwin Conklin

Question 9

importance of fate maps

1. essential tool in most embryological experiments
2. provide researchers with information on which portions of the embryo will normally become which larval or adult structure
3. way of tracing a particular region as it develops from an early embryo into a differentiated body plan
4. understanding an organism’s developmental pathway
5. understanding the lineage and migration of progenitor cells can lead to the discovery of _
6. determining the function of each specific region

Answer 9

gene regulatory networks and signaling pathways

Question 10

Construction of Fate Map by following methods

Answer 10

1. Observing Living Embryos/ Natural Markings
2. Vital Dye Marking/ Vital Staining
3. Carbon Particle Marking
4. Radioactive (Isotope) Labelling and Fluorescent Dyes

Question 11

radioactive isotope
such as _ are used to label the early blastomeres

Answer 11

C14 and P

Question 12

Carbon Particle Marking - s introduced by

Answer 12

Spratt (1946)

Question 13

A sort of “mark” can be made on, or inside the egg or embryo using agents
such as:

Answer 13

a. charcoal
b. dye
c. soot
d. fluorescent molecules (rhodamine-conjugated dextran)
e. proteins like green fluorescent protein (GFP)
f. enzymes encoded by injected genes or mRNAs

Question 14

one way of making the fate map is by staining the various parts of the early embryo with a lipophilic dye such as _ and observe where the labelled regions end up

Answer 14

dil

Question 15

another sophisticated way of labelling the blastomeres is by injection of high molecular weight molecules such as _ , which cannot pass through cell membrane and are, therefore, **restricted to the injected cell ** and its progeny

Answer 15

rhodamine-labelled dextran

these cells can be easily detected later, under a UV microscope