Patterning + Differentiation (lec 2/3/4) Flashcards
What are the two major types of cleavages?
Briefly describe them
1) Holoblastic: complete; whole embryo involved
2) Meroblastic: incomplete; cleavage occurs at certain regions; not the whole embryo
What are the two types of holoblastic cleavages?
Briefly describe them.
A) Isolecithal - Sparse, evenly distributed yolk
B) Mesolecithal - Moderate vegetal yolk disposition
What are the two types of meroblastic cleavage?
A) Telolecithal - Dense yolk throughout most of cell
B) Centrolecithal - yolk in center of egg
What are the four types of isolecithal cleavages?
1) Radical cleavage
2) Spiral cleavage
3) Bilateral cleavage
4) Rotational cleavage
What are the two types of telolecithal cleavages?
1) Bilateral cleavage
2) Discoidal cleavage
Match the different types of movements to their descriptions:
1) Invagination
2) Involution
3) Ingression
4) Delamination
5) Epiboly
A) Migration of individual cells from the surface into the embryo’s interior. Individual cells become mesenchymal (i.e., separate from one another) and migrate independently.
B) Movement of epithelial sheets (usually ectodermal cells) spreading as a unit (rather than individually) to enclose deeper layers of the embryo. Can occur by cells dividing, by cells changing their shape, or by several layers of cells intercalating into fewer laters; often, all three mechanisms are used.
C) Infolding of a sheet (epithelium) of cells, much like the indention of a soft rubber ball when it is poked.
D) Spitting of one cellular sheet into two more or less parallel sheets. While on a cellular basis it resembles ingression, the result is the formation of a new (additional) epithelial sheet of cells.
E) Inward movement of an expanding outer layer so that it spread over the internal surface of the remaining external cells.
Invagination: Infolding of a sheet (epithelium) of cells, much like the indention of a soft rubber ball when it is poked.
Involution: Inward movement of an expanding outer layer so that it spreads over the internal surface of the remaining external cells.
Ingression: Migration of individual cells from the surface into the embryo’s interior. Individual cells become mesenchymal (i.e., separate from one another) and migrate independently.
Delamination: Spitting of one cellular sheet into two more or less parallel sheets. While on a cellular basis it resembles ingression, the result is the formation of a new (additional) epithelial sheet of cells.
Epiboly: Movement of epithelial sheets (usually ectodermal cells) spreading as a unit (rather than individually) to enclose deeper layers of the embryo. Can occur by cells dividing, by cells changing their shape, or by several layers of cells intercalating into fewer layers; often, all three mechanisms are used.
What are the three major primary axes?
1) Midsagittal plane
2) Horizontal plane (lateral)
3) Transverse plane (cross section)
Match the different germ layers (+cells) to what they develop into:
1) Ectoderm (outer layer)
2) Mesoderm (middle layer)
3) Endoderm (internal layer)
4) Germ cells
A) digestive tube (stomach cell), pharynx (thyroid cell), respiratory tube (lung cell)
B) outer surface (skin), central nervous system, neural crest (pigment cell)
C) male (sperm), female (egg)
D) dorsal (notochord), paraxial (bone tissue), intermediate (tubule cell of the kidney), lateral (red blood cells), and head (facial muscle)
Ectoderm (outer layer): outer surface (skin), central nervous system, neural crest (pigment cell)
Mesoderm (middle layer): dorsal (notochord), paraxial (bone tissue), intermediate (tubule cell of the kidney), lateral (red blood cells), and head (facial muscle)
Endoderm (internal layer): digestive tube (stomach cell), pharynx (thyroid cell), respiratory tube (lung cell)
Germ cells: male (sperm), female (egg)
(T/F) The cells that form gill supports in fish form the middle ear bones in mammals.
True!
In adult fish, PHARYNGEAL ARCH (branchial arch) cells form the _________ jaws and ______ arches.
In amphibians, birds, and reptiles, these same cells form the _______ bone of the _______ jaw and the _______ bone of the ______ jaw.
In mammals, the _______ has become internalized and forms the ______ of the middle ____. The ________ bone retains its contact with the _______, becoming the _______ of the middle ear.
hyomandibular; gill
quadrate; upper, articular; lower
quadrate; incus; ear
articular; quadrate; malleus
(T/F) Edwin Conklin mapped the fates of early cells of the tunicate (styela partita) using the fact that in embryos of this species many of the cells can be identified by their different-colored cytoplasms. Yellow cytoplasm marks the cells that form the red blood cells.
False!
Yellow cytoplasm marks the cells that form the trunk muscles.
*at the 8-cell stage, two of the eight blastomeres contain the yellow cytoplasm, which were present in the newly formed trunk muscles at the early larval stage.
An older cell fate mapping technique is using the vital dye staining. Briefly describe this process.
Agar chips with dye are implanted in different parts of the embryo (in the example given, it was an amphibian embryo).
This allowed the the dyed cells to be traced through the developmental phases of the embryo.
A more recent cell fate mapping technique is using a fluorescent dye. Briefly describe this process using the zebrafish embryo example.
In zebrafish embryo, specific cells were injected with a fluorescent dye that does NOT DIFFUSE FROM THE CELLS. The dye was THEN ACTIVATED BY LASER in a small region (~5 cells) of the late-cleavage-stage embryo.
After formation of the CNS had begun, the cells that contained the activated dye were VISUALIZED BY FLUORESCENT LIGHT. The fluorescent dye was seen in cells that generate the forebrain and midbrain.
*In this process, the animals can be GMO and make their own dyes at certain times.
Genetic markers can be used as cell lineage tracers (fate mapping). Briefly describe this process using the quail and chick example.
Cells from a particular region (that produces cells that populate the neural tube) of a 1-day QUAIL embryo have been GRAFTED into a similar region of a 1-day CHICK embryo. After several days, the quail cells can be seen by using an ANTIBODY TO QUAIL-SPECIFIC PROTEINS.
The neural crest cells that gave rise to the pigment migrated into the wing epidermis and feathers of a chick resulting from transplantation of a trunk neural crest region from an embryo of a PIGMENTED STRAIN OF CHICKENS into the SAME REGION of an embryo of an UNPIGMENTED STRAIN.
How can chick and quail cells be distinguished besides using antibodies for quail/chick specific proteins?
They can be also distinguished by the heterochromatin of their nuclei.
Quail cells have single large nucleus, while chick cells have a diffused nuclei.
Fate mapping with transgenic DNA shows that the _______ ____ is critical in making the gut neurons.
How was this discovered?
Neural Crest
A chick embryo contained an active gene for green fluorescent protein, causing it to express GFP in every cell. The region of the neural tube and crest was excised and transplanted into a similar position in an unlabelled wild-type embryo. The neural crust cells (that expressed the GFP) were near the foregut.
(T/F) The vertebrates—fish, amphibians, reptiles, birds and mammals—all start development very differently because of the enormous differences in the size of their eggs. They remain different throughout the whole process.
False!
Though they all start development very differently because of the enormous differences in the size of their eggs, there are certain stages where their embryos are VERY SIMILAR as the organs developed then have critical functions.
(T/F) Animals in adult form can look very different from one another, but look very similar during embryogenesis.
True!
Barnacles and shrimp both exhibit a distinctive ______ stage (the nauplius) that underscores their common ancestry as _________ __________.
Before this discovery, barnacles were classified as ___________, which are sedentary, differing in body form and lifestyle from the free-swimming adult shrimp.
Larval; crustacean arthropods.
Mollusks
Tunicates are also known as _____ _______.
Larval stage of ascidian tunicate, C. intestinalis, reveal its common ancestry with other __________ as they had a dorsal ______ _____ and a _____________.
Before this, they were grouped as ________.
sea squirt
chrodates; nervous sytem; notochord
mollusks
