NEUROBIOLOGY LATEST 2026 EXAM QUESTIONS AND
ANSWERS GRADED A+
✔✔Gastrulation - ✔✔The time during which all of the cells in this early embryo (blastula)
start migrating around, changing from a uniform ball of cells into a gastrula, which has
already defined three layers which will make up your whole body - ectoderm,
mesoderm, endoderm.
They have to be properly aligned - *3D cell movements*
✔✔Organogenesis - ✔✔Three layers start to make internal organs so system can start
to function.
✔✔Metamorphosis - ✔✔Maturation
✔✔Gametogenesis - ✔✔Creation of gametes so cycle can start all over again
✔✔The Germ layers: formed during gastrulation - ✔✔Three distinct regions of the
embryo that give rise to differentiated cell types and specific organ function.
Outer: ectoderm
Middle: Mesoderm
Inner: endoderm
✔✔The discovery of the primary germ layers - ✔✔- 3 individuals established the science
of embryology
- Christian Pander, Karl Ernst von Baer, and Heinrich Rathke.
Pander discovered the germ layers
✔✔The Germ layers - ✔✔Three distinct regions of the embryo that give rise to
differentiated cell types and specific organ systems.
Ectoderm:
- outer layer = skin, brain, neural crest.
*Nervous system*
Mesoderm:
- middle layer = blood, heart, kidney, gonads, bones, muscles, and connective tissue
Endoderm:
- inner layer = digestive tube and associated organs including the lungs.
,✔✔Which germ layer gives rise the CNS? - ✔✔Ectoderm
✔✔The germ layers are formed during which stage of development? - ✔✔Gastrulation
✔✔What developmental stage results from cleavage ie. multiple rounds of cell division?
- ✔✔Blastula
✔✔How does the blastula become a gastrula which becomes an adult? - ✔✔A
complicated series of cell movements and shape changes allow the formation of the
axis.
Cell migration and folding: The cells of the blastula undergo dramatic and coordinated
movements, pushing inward to form a multi-layered structure called a gastrula.
Formation of germ layers: This process establishes the three primary germ layers. This
dramatically reorganizes the embryo and establishes the major body axes
(anterior/posterior, dorsal/ventral). From these three layers, all tissues and organs of the
adult develop during subsequent stages like organogenesis.
Establishment of body plan: Gastrulation establishes the basic body plan and sets the
stage for future development.
✔✔Formation of the body axis and organs - ✔✔How do cells know what to become and
when do they know?
Induction and specification
✔✔Specification - ✔✔The first stage of commitment of cell or tissue fate during which
the cell or tissue is capable of differentiating autonomously (by itself) when placed in an
environment that is neutral with respect to the developmental pathway.
At the stage of specification, cell commitment is capable of being reversed if placed in
another environment that is not neutral.
✔✔Induction - ✔✔The process by which one cell population influences the development
of neighboring cells via interactions at close range.
- this is the environment that can alter specification.
✔✔After induction and specification come *differentiation* - ✔✔The process by which
an unspecialized cell becomes specialized into one of the many cell types that makes
up the body.
After differentiation occurs, its VERY hard to change what the cell is.
,✔✔Waddington's Developmental Landscape - ✔✔The end result of these related
processes is the production of specific tissues in the right location.
Right tissue, right place, right time.
Once you roll one way, its really hard to go back up the hill.
✔✔Formation of the body axis and organs (2/2) - ✔✔How do cells know what to
become and when do they know?
- autonomous specification
- conditional specification
✔✔Autonomous specification - ✔✔Characteristic of most invertebrates
- differential acquisition of cytoplasmic molecules present in the egg control what the
cell becomes
- invariant cleavage produces the same lineage in each embryo of the species
- cell type specification precedes cell migration
- bottom line: cells cannot change fate!! Even when some cells are lost.
Induction can't happen - cells already know what they are going to be - if lose part of
embryo - just lose that part of the animal. Cells cant change to compensate. All or
nothing.
✔✔Conditional specification - ✔✔Found in most vertebrates
- cell specification depends on environment and neighboring cells.
- each cell is pluripotent (can be many things)
- cell fate is restricted based on external cues.
- Bottom line = cell fate is malleable and can be altered to a certain point.
Transplanted cells differentiate into tissue that correspond to new embryonic region.
Cell removal does not cause any defects in animal - other cells can replace them.
✔✔Cells that will give rise to certain tissues have their fate determined during
gastrulation. - ✔✔Fate map: identification of groups of cells in the gastrula that will
become a particular tissue in the adult.
WHEN cells have their identity and WHEN cells lose the ability to go into a different fate.
Fate mapping studies to label individual cells and track them over time.
- method 1: fluorescent dye labeling. Inject cells with tracking dye, see where they go.
Putting pluripotent cells into different areas of the gastrula, can show differentiation
based on location environment.
, Tells that during gastrulation, something happens to cells to push them down towards
differentiation.
- method 2: chimeric organisms ie. quail chick chimeras. Transplant cells from quail
embryos into chick, see where they go.
How do we identify quail cells in a chick?
1. differences in nuclear DNA condensation
2. quail specific antibodies - immunohistochemistry! Process through which you can
antibody label something. Antigens on cell surface - can design antibody to bind to
antigen - label cells from quail.
✔✔Chimeric organisms revealed the diversity of tissues derived from *neural crest*. -
✔✔Population of cells that gives rise to glia and neurons of the PNS and enteric
nervous system (GI)
- neural crest arises from the ectoderm
- adjacent to developing nervous system
- delaminates (lose cell-cell contacts) and migrates away.
✔✔What do the neural crest become? - ✔✔Cranial Neural Crest
- chondrocytes
- osteocytes
-connective tissue
Cardiac Neural Crest
- cardiomyocytes
- glial cells
Trunk Neural Crest
- Dorsal root ganglia
- pigment cells
*Enteric nervous system (digestive) and peripheral nervous system come from neural
crest*
Defects in neural crest migration cause cleft palates.
Cell transplantation shows us a lot!
- Transplant neural crest from pigmented chicken embryo into albino yields black
feathers. Shows that the neural crest is the root of many different types of cells.
✔✔Induction of the nervous system-beginning of development of the nervous system -
✔✔What is induction?
ANSWERS GRADED A+
✔✔Gastrulation - ✔✔The time during which all of the cells in this early embryo (blastula)
start migrating around, changing from a uniform ball of cells into a gastrula, which has
already defined three layers which will make up your whole body - ectoderm,
mesoderm, endoderm.
They have to be properly aligned - *3D cell movements*
✔✔Organogenesis - ✔✔Three layers start to make internal organs so system can start
to function.
✔✔Metamorphosis - ✔✔Maturation
✔✔Gametogenesis - ✔✔Creation of gametes so cycle can start all over again
✔✔The Germ layers: formed during gastrulation - ✔✔Three distinct regions of the
embryo that give rise to differentiated cell types and specific organ function.
Outer: ectoderm
Middle: Mesoderm
Inner: endoderm
✔✔The discovery of the primary germ layers - ✔✔- 3 individuals established the science
of embryology
- Christian Pander, Karl Ernst von Baer, and Heinrich Rathke.
Pander discovered the germ layers
✔✔The Germ layers - ✔✔Three distinct regions of the embryo that give rise to
differentiated cell types and specific organ systems.
Ectoderm:
- outer layer = skin, brain, neural crest.
*Nervous system*
Mesoderm:
- middle layer = blood, heart, kidney, gonads, bones, muscles, and connective tissue
Endoderm:
- inner layer = digestive tube and associated organs including the lungs.
,✔✔Which germ layer gives rise the CNS? - ✔✔Ectoderm
✔✔The germ layers are formed during which stage of development? - ✔✔Gastrulation
✔✔What developmental stage results from cleavage ie. multiple rounds of cell division?
- ✔✔Blastula
✔✔How does the blastula become a gastrula which becomes an adult? - ✔✔A
complicated series of cell movements and shape changes allow the formation of the
axis.
Cell migration and folding: The cells of the blastula undergo dramatic and coordinated
movements, pushing inward to form a multi-layered structure called a gastrula.
Formation of germ layers: This process establishes the three primary germ layers. This
dramatically reorganizes the embryo and establishes the major body axes
(anterior/posterior, dorsal/ventral). From these three layers, all tissues and organs of the
adult develop during subsequent stages like organogenesis.
Establishment of body plan: Gastrulation establishes the basic body plan and sets the
stage for future development.
✔✔Formation of the body axis and organs - ✔✔How do cells know what to become and
when do they know?
Induction and specification
✔✔Specification - ✔✔The first stage of commitment of cell or tissue fate during which
the cell or tissue is capable of differentiating autonomously (by itself) when placed in an
environment that is neutral with respect to the developmental pathway.
At the stage of specification, cell commitment is capable of being reversed if placed in
another environment that is not neutral.
✔✔Induction - ✔✔The process by which one cell population influences the development
of neighboring cells via interactions at close range.
- this is the environment that can alter specification.
✔✔After induction and specification come *differentiation* - ✔✔The process by which
an unspecialized cell becomes specialized into one of the many cell types that makes
up the body.
After differentiation occurs, its VERY hard to change what the cell is.
,✔✔Waddington's Developmental Landscape - ✔✔The end result of these related
processes is the production of specific tissues in the right location.
Right tissue, right place, right time.
Once you roll one way, its really hard to go back up the hill.
✔✔Formation of the body axis and organs (2/2) - ✔✔How do cells know what to
become and when do they know?
- autonomous specification
- conditional specification
✔✔Autonomous specification - ✔✔Characteristic of most invertebrates
- differential acquisition of cytoplasmic molecules present in the egg control what the
cell becomes
- invariant cleavage produces the same lineage in each embryo of the species
- cell type specification precedes cell migration
- bottom line: cells cannot change fate!! Even when some cells are lost.
Induction can't happen - cells already know what they are going to be - if lose part of
embryo - just lose that part of the animal. Cells cant change to compensate. All or
nothing.
✔✔Conditional specification - ✔✔Found in most vertebrates
- cell specification depends on environment and neighboring cells.
- each cell is pluripotent (can be many things)
- cell fate is restricted based on external cues.
- Bottom line = cell fate is malleable and can be altered to a certain point.
Transplanted cells differentiate into tissue that correspond to new embryonic region.
Cell removal does not cause any defects in animal - other cells can replace them.
✔✔Cells that will give rise to certain tissues have their fate determined during
gastrulation. - ✔✔Fate map: identification of groups of cells in the gastrula that will
become a particular tissue in the adult.
WHEN cells have their identity and WHEN cells lose the ability to go into a different fate.
Fate mapping studies to label individual cells and track them over time.
- method 1: fluorescent dye labeling. Inject cells with tracking dye, see where they go.
Putting pluripotent cells into different areas of the gastrula, can show differentiation
based on location environment.
, Tells that during gastrulation, something happens to cells to push them down towards
differentiation.
- method 2: chimeric organisms ie. quail chick chimeras. Transplant cells from quail
embryos into chick, see where they go.
How do we identify quail cells in a chick?
1. differences in nuclear DNA condensation
2. quail specific antibodies - immunohistochemistry! Process through which you can
antibody label something. Antigens on cell surface - can design antibody to bind to
antigen - label cells from quail.
✔✔Chimeric organisms revealed the diversity of tissues derived from *neural crest*. -
✔✔Population of cells that gives rise to glia and neurons of the PNS and enteric
nervous system (GI)
- neural crest arises from the ectoderm
- adjacent to developing nervous system
- delaminates (lose cell-cell contacts) and migrates away.
✔✔What do the neural crest become? - ✔✔Cranial Neural Crest
- chondrocytes
- osteocytes
-connective tissue
Cardiac Neural Crest
- cardiomyocytes
- glial cells
Trunk Neural Crest
- Dorsal root ganglia
- pigment cells
*Enteric nervous system (digestive) and peripheral nervous system come from neural
crest*
Defects in neural crest migration cause cleft palates.
Cell transplantation shows us a lot!
- Transplant neural crest from pigmented chicken embryo into albino yields black
feathers. Shows that the neural crest is the root of many different types of cells.
✔✔Induction of the nervous system-beginning of development of the nervous system -
✔✔What is induction?
