Introduction to Developmental Biology Flashcards
(201 cards)
1
Q
What three areas is modern developmental biology a combination of?
A
Embryology
Cytology
Genetics
2
Q
What is the overarching aim of developmental biology?
A
To understand the genetic and cellular mechanims that produce a comple multi-cellular organism from a single cell
3
Q
What does pattern formation require?
A
Differential gene expression
Signalling between cells
4
Q
What are the 6 stages that pattern formation arises through?
A
Cell proliferation Cell migration Changes in cell shape and size Cell differentiation Cell interaction Apoptosis
5
Q
What are the two major cell types in the early developing embryo?
A
Epithelial cells
Mesenchymal cells
6
Q
What are the characteristics of epithelial cells?
A
Polarised Sit on a basement membrane Cell-to-cell junctions Usually have motile cilia Marker genes (i.e. cytokeratin)
7
Q
What are the characteristics of mesenchymal cells?
A
Not polarise
Not joined to others cells (i.e. motile)
Marker genes (i.e. vimetin)
Lie within a matrix
8
Q
A cell that is destined to become a square is relocated to amongst cells that are destined to become circles. The cell become a circle cell. What can you say about its cell fate commitment?
A
It is specified but not determined
9
Q
A cell that is destined to become a square is relocated to amongst cells that are destined to become circles. The cell become a square cell. What can you say about its cell fate commitment?
A
It is determined
10
Q
What is cell fate restriction governed by?
A
Cell’s genome (gene expression)
Cell’s history (factors it has been exposed to, where it has moved from)
Interaction with its neighbours
11
Q
What are the advantages of using Drosophila and round worms to model normal and abnormal human development?
A
Easy to keep; rapid life cycle (10 days in fly, 3 days in worm)
Easy to genetically modify over multi-generations; key genes known
Fate of most or all cells known
12
Q
What are the disadvantages of using Drosophila and round worms to model normal and abnormal human development?
A
Many aspects of development and anatomy are not conserved with humans
13
Q
What are the advantages of using zebra fish and African clawed frog to model normal and abnormal human development?
A
Easy to keep; can add factors to the environment (water
Easy to manipulate as embryo develops outside maternal body
14
Q
What are the disadvantages of using zebra fish and African clawed frog to model normal and abnormal human development?
A
Distant from humans; some features not shared (mammary glands)
15
Q
What are the advantages of using chicks to model normal and abnormal human development?
A
Closer to humans
Easy to manipulate as embryo develops outside maternal body
Early embryogenesis is very similar to humans
16
Q
What are the disadvantages of using chicks to model normal and abnormal human development?
A
Longer life cycle (4 months); transgenic strategies lag behind mice
17
Q
What are the advantages of using mice to model normal and abnormal human development?
A
Same organ systems and many of the same diseases as humans
Relatively easy to maintain colonies; advanced transgenic available
18
Q
What are the disadvantages of using mice to model normal and abnormal human development?
A
Embryos develop in utero
Can be expensive to generate null mutants
Models can sometimes show different phenotypes to human disease
19
Q
Some cells of a frog embryo that would give rise to the gut are transplanted into the future head region and still develop into intestinal epithelial cells.
Which word best describes the cells at the time of transplantation?
a) they are specified
b) they are determined
c) they demonstrate fate mapping
d) they are differentiated
e) none of the above
A
b) they are determined
20
Q
Differential gene expression occurs due to interaction between ___________ (working within a cell) and __________ (working between cells)
A
Transcription factors; signalling molecules
21
Q
What are the regulatory elements that control gene expression?
A
Promoters
Enhancers
Inhibitors
22
Q
What is an example of homeotic transformation?
A
Antennapedia (legs where antennae should be)
23
Q
How are homeotic transformations caused?
A
Mutation in relevant Hox gene
24
Q
How many Hox clusters do mammals have?
A
Four
25
What is it called when one gene can compensate for the loss of a related one?
Functional redundency
26
How would you determine the role of a gene found to be expressed in the brain?
Knockout the gene and observe the phenotype
27
How would you determine the role of a gene found to be expressed in the brain when it is also expressed in several other sites?
Conditional knockout
28
What are the main type of paracrine signalling molecules?
Fibroblast growth factors (FGFs)
Hedgehog
Wnt
Transforming growth factor-β (TGF-β)
29
What is a change in cell fate due to signals sent from other cells called?
Induction
30
What factors determine how a cell will respond to morphogens?
```
Other signals it is currently receiving
Cell memory (past signals it has received)
```
31
What type of inhibition is the Notch signaling pathway?
Lateral inhibition
32
How does the Notch signalling pathway occur?
Direct interaction between the cell surface receptor (Notch) on the receiving cell and a ligand (Delta, Jagged or Serrate) on the signalling cell. When the receptor is activated, a protease cleaves part of the receptor that enters the nucleus and promotes the transcription of a particular gene
33
What are the three types of signalling?
Autocrine
Paracrine
Endocrine
34
What are the two type of receptors that paracrine factors activate and how do they induce phosphorylation?
1. Those with intrinsic protein kinase activity (phosphorylates downstream factors)
2. Those that use a second messenger system to activate cytoplasmic kinases
35
What type of recepor does fibroblast growth factors (FGFs) activate?
Receptor tyrosine kinases (RTK)
36
What functions of FGFs play in development?
Cell proliferation
Promotion of angiogenesis
Activation/suppression of other pathways
37
What is the mechanism by which FGFs activate/supress gene transcription?
FGFs bind to the receptor tyrosine kinase which activates a G-protein which activates RAS which activates RAF which activates a MAP kinase which activates ERK which phsophorylates a transcription f1actor
38
Where is Fgf8 mRNA expressed in a chicken embryo?
Outer epithelial of limb bud
39
What happens when a bead carrying Fgf8 is implanted into the embryo?
An extra limb can form
40
Which of the following is an example of a morphogen?
a) a transcription factor that can bind more than one target gene
b) an endocrine signal that can influence how cells behave
c) a diffusible protein that influences cell fate
d) a cell that induces its neighbours to follow a developmental fate
c) a diffusible protein that influences cell fate
41
What receptor does transforming growth factor-β (TGF-β) use?
Serine/theronine kinase receptor
42
How does TGF-β influence the transcription of a gene?
Activation of the receptor leads to activation of Smad proteins that combine to form a dimer which then combines with a cofactor in the nucleus and interacting with the DNA
43
What function does TGF-β play in development?
Cell specification
Regulating extracellular matrix formation
Cell division
Cell death
44
What can make TGF-β functionally redundant?
Bone Morphogenetic Proteins (BMPs)
45
What are essential regulators of chondrogenesis (cartilage formation)?
Bone Morphogenetic Proteins (BMPs)
46
Which signalling pathway is essential for gastrulation?
Wnt signalling pathway
47
How does the Wnt pathway influence gastrulation?
It defines that dorsal side of the embryo; assists with neural tube formation, cells proliferation, polarity and differentiation
48
How does Hedgehog activate transcription?
Hedgehog binds to a patched (PTC) receptor, preventing it from inhibiting SMO meaning that SMO can prevent the phosphorylation and deactivation of the transcription factor Gli. Gli can then enter the nucleus and promote transcription
49
What are the two important drivers of morphogenesis?
Direct cell-to-cell adhesion
| Cell migrationl
50
How can boundaries between cells be created?
Cells having different types and different amounts of cell surface molecules called cell adhesion molecules
51
What type of cadherin is found on most early embryonic cells and later in epithelial tissues?
E-cadherins
52
What type of cadherin is found on neural cells?
N-cadherins
53
What type of cadherin is found on placental cells?
P-cadherins
54
True or False:
| Both epithelial and mesenchymal cells migrate
True
| Epithelial as sheets or tubes
55
How do epithelial cells migrate?
The polarity of the cell changes due to signals. Actin filaments assemble at the leading edge of the cell and provide mechanical force. The cell interacts with extracellular matrix, particularly integrins which pull the cell along. Myosin also provides motile force along the actin filaments
56
Which experiment below shows that Fgf4 is sufficient for limb development in the chicken embryo?
a) Implant a bead expressing Fgf4 and observe an extra limb forming
b) Knock out the gene and note loss of limb during development
c) Show that Fgf4 is expressed in the forming limb using in situ hybridisation
d) All of the above
a) Implant a bead expressing Fgf4 and observe an extra limb forming
b) is incorrect because it shows that it is required not sufficient
57
What are the four types of cell potency?
Totipotent
Pluripotent
Multipotent
Unipotent
58
What are individual cells called during the cleavage stage?
Blastomeres
59
What cadherin mediates compaction at the 8-cell stage of cleavage?
E-cadherins
60
What is the compacted ball of cells called during cleavage?
Morula
61
When the inner cells move to one side of the morula, creating a cavity, what is the ball of cells called?
Blastocyst
62
Which part of the blastocyst is ES cells found?
Inner cell mass
63
The cells that move to one side of the morula are called what?
Inner cell mass
64
The cells on the outside of the blastocyst are called what?
Trophoblast
65
What pluripotency factors do cells in the inner cell mass express?
Oct4, Nanog and Sox2
66
A blastomere exposed to Oct4 will become what?
Inner cell mass
67
A blastomere exposed to Cdx2 will become what?
Trophoblast
68
An inner cell mass cell exposed to Nanog` will become what?
Epiblast
69
An inner cell mass cell exposed to Gata 6` will become what?
Hypoblast
70
What must a blastomere be exposed to in order to become an epiblast cell?
Oct4 and then Nanog
71
The first cells to migrate through the primitive streak and displace the hypoblast become what?
Endoderm
72
The second cells to migrate through the primitive streak and displace the hypoblast become what?
Mesoderm
73
Where is the primitive streak found?
The caudal (tail) end of the embryo
74
What are the two key organisers that develop in the early mammalian blastocyst?
1. A specialised group of cells in the hypoblast (Anterior Visceral Endoderm (AVE) in mice)
2. Primitive streak
75
What is the primitive node?
A dynamic mass of cells at the anterior tip of the primitive streak
76
Which signalling molecules are responsible for the positioning of the primitive streak?
Nodal, FGFs and Wnts
77
What signalling molecules are highest at the posterior?
Wnts, BMPs and FGFs
78
What signalling molecules are highest at the anterior?
BMP and Wnt antagonists
79
From which structure in the late blastocyst does the entire embryo develop?
Epiblast
80
What parts of the body does the ectoderm differentiate into?
```
Skin and its derivatives
Nerves and sensory systems
Pituitary gland and adrenal medulla
Jaw and teeth
Neural crest cells
```
81
What parts of the body does the mesoderm differentiate into?
```
Skeleton and muscles
Circulatory and lymphatic systems
Excretory and reproductive systems (not germ cells)
Dermis
Adrenal cortex
```
82
What parts of the body does the endoderm differentiate into?
Epithelial lining of the digestive tract and associated organs
Epithelial lining of respiratory, excretory and reproductive tracts
Thymus, thyroid and parathyroid glands
83
What are the four main tissue types?
Epithelium
Connective tissue
Muscle
Nerves
84
Which two key structure form towards the end of gastrulation?
Notochord and neural tube
85
Which signalling molecule induces neurulation?
Hedgehog
86
What is the name given to the decendants of epiblast cells that do not pass through the primitive streak?
Ectoderm
87
An early mouse embryo dies very early in development and is found to have a swollen brain, skin, but stumps instead of limbs, and no eidence of a skeleton. This could be due to an early developmental defect in an aspect of:
a) Ectoderm specification
b) Endoderm specification
c) Mesoderm specification
d) Cleavage
c) Mesoderm specification
88
What are the two broad types of stem cells?
Embryonic stem cells (ES cells)
| Adult stem cells
89
What are the three main potential uses of stem cells?
Regenerative medicine
Modelling and treating human disease
Understanding and treating birth defects
90
Where is Oct4 expressed?
Inner cell mass
91
What are potential problems with ES cells?
Heterogenous cell populations are often produced
The transplanted cells may not behave normally
Tumourigenic potential
Immunological rejection
Ethical concerns
92
You have isolated what you believe to be pancreatic beta stem cells. What evidence would you need that they are pancreatic stem cells?
1. Self renew in culture
2. Express pancreatic cell markers in culture
3. Can behave as beta cells in vivo (e.g. insulin production in mice)
93
What is the difference between embryonic and adult stem cells?
```
Embryonic:
Pluripotent
Immune rejection possible
Tumour potential
Ethical concerns
```
```
Adult:
Multipotent
Immune rejection unlikely
Less likely to form tumours
Less ethical concerns
```
94
Which four factors are required to create iPS cells?
Oct4, Sox2, c-Myc and Klf4
95
What does Oct4 and Sox2 do in the creation of iPS cells?
Activate Nanog to establish pluripotency and block differentiation
96
What does c-Myc do in the creation of iPS cells?
Opens chromatin; makes genes accessible to Sox2, Oct4 and Nanog
97
What does c-Klf4 do in the creation of iPS cells?
Prevents cells death
98
What are the advantages of using iPS cells instead of ES cells?
1. They are patient specific (no immune rejection)
| 2. No ethical concern
99
Which statement is true?
a) iPS cells are derived from the inner cell mass
b) The Tamanaka reprogramming factors are growth factors
c) Therapeutic cloning typically involves transplanting an embryo into a recipient female host
d) iPS cells are totipotent
e) None of the above
e) None of the above
100
What is an adult stem cell?
a multipotent stem cell derived from mature organs that play a role in homeostasis. They are found in regulated microenvironments called stem cell niches
101
What is angiogenesis?
the growth of new blood vessels that tumours need to grow. This process is caused by the release of chemicals by the tumour and by the host cells near the tumour
102
What is the anterior visceral endoderm (ACE)?
a key signalling centre in the late blastocyst that establishes the anterior-posterior axis and dictates where the primitive streak will form
103
What does autocrine mean?
a type of signalling where a substance is secreted by a cell and acting on surface receptors of the same cell
104
Define bilaminar disc
an embryonic structure that appears as a disc composed of epiblast and hypoblast. These two layers are sandwiched between two balloons: the primitive yolk sac and the amniotic cavity
105
Define bone morphogenetic proteins (BMP)
a member of a superfamily of proteins that promote the formation of bone and the skeleton and help mend broken bones.
106
Define blastocyst
a thin-walled hollow structure in early embryonic development that contains a cluster of cells called the inner cell mass from which the embryo arises. The outer layer of cells gives rise to the placenta and other supporting tissues needed for fetal development within the uterus while the inner cell mass cells gives rise to the tissues of the body
107
Define cadherins
calcium-dependent adhesion molecules that are essential for establishing and maintaining intracellular connections. They play a crucial role in spatial segregation of cell types and morphogenesis
108
Define cell fate
the developmental destination of a cells if left undisturbed in the embryo
109
Define cell fate commitment
the commitment of cells to specific cell fates and their capacity to differentiate into particular kinds of cells
110
Define cell fate determination
a process involved in cell fate commitment. Once determination has taken place, a cell becomes committed to differentiate down a particular pathway regardless of its environment
111
Define cell fate specification
a form of embryonic specification in which a developing cell is able to differentiate (become a cell carrying out a specialised function) without receiving external signals
112
Define cell differentiation
the expression of a developmental fate where a cell adopts its final phenotype allowing it to express proteins that allow it to perform its function
113
Define cell migration
a central process in the development and maintenance of multicellular organisms. Tissue formation during embryonic development, wound healing and immune responses all require the orchestrated movement of cells in particular directions to specific locations
114
Define cell proliferation
the process that results in an increase of the number of cells, and is defined by the balance between cell divisions and cell loss through cell death or differentiation
115
Define cell-to-cell adhesion
the process by which cells interact and attach to neighbouring cells through specialised molecules of the cell surface. This process can occur either through direct contact between cell surfaces or indirect interaction, where cells attach to surrounding extracellular matrix, a gel-like structure containing molecules released by cells into spaces between them
116
Define cleavage
the repeated division of a fertilized ovum, producing a cluster of cells with the same size as the original zygote
117
Define combinatorial signalling
the effect of multiple signalling molecules on cellular function
118
Define conditional knockout
a technique used to eliminate a specific gene in a certain tissue, such as the brain. This technique is useful to study the role of individual genes in living organisms
119
Define congenital birth defects
a condition that is present at birth due to structural deformities in the development of a fetus. Common examples of congenital birth defects include congenital heart disease, neural tube defects and Down syndrome
120
Define cytology
the branches of biology and medicine concerned with the structure and function of plant and animal cells
121
Define developmental biology
the study of how organisms grow and develop
122
Define DNA-binding proteins
proteins that have DNA-binding domains and this have a specific or general affinity for sing- or double-stranded DNA
123
Define ectoderm
the outermost of the three germ layers, or masses of cells, which appears early in the development of an animal embryo. In vertebrates, ectoderm subsequently gives rise to hair, skin, nails or hooves, and the lens of the eye; the epithelia of sense organs, the nasal cavity, the sinuses, the mouth , and the anal canal; and nervous tissue, including the pituitary body and chromaffin tissue
124
Define epithelial cells
any one of several cells arranged in one or more layers that form part of a covering or lining of a body surface. The cells usually adhere to one other along their edges and surfaces. One surface is free, and the other rests on a noncellular basement membrane
125
Define epithelial to mesenchymal (EMT)
a process by which epithelial cells lose their cell polarity and cell-cell adhesion, and gain migratory and invasive properties to become mesenchymal stem cells; these are multipotent stromal cells that can differentiate into a variety of cell types. EMT is essential for numerous developmental processes including mesoderm formation and neural tube formation
126
Define embryogenesis
the process by which the embryo forms and develops
127
Define embryoid bodies
three-dimensional aggregates of pluripotent stem cells. The pluripotent cell types that comprise embryoid bodies include embryonic stem cells (ESCs) derived from the blastocyst stage of embryos from mouse (mESC), primate, and human (hESC) sources
128
Define embryonic induction
the embryonic process in which one group of cells, the inducing tissue, directs the development of another group of cells, the responding tissue. Induction directs the development of various tissues and organs in most animal embryos; for example, the eye lens and the heart
129
Define embryonic stem cells
a pluripotent stem cell derived from inner cell mass that has wide differentiation potential
130
Define endocrine
the secretion of molecules that are distributed in the body by way of the bloodstream
131
Define endoderm
the innermost of the three primary germ layers of an embryo that is the source of the epithelium of the digestive tract and its derivatives and of the lower respiratory tract
132
Define epiblast
one of two distinct layers arising from the inner cell mass in the mammalian blastocyst that gives rise to the three primary germ layers (ectoderm, definitive endoderm, and mesoderm)
133
Define fate map
a diagram that maps adult tissues or structure to regions of the embryo that gives rise to that structure
134
Define fibroblast growth factors (FGFs)
a family of cell signalling proteinsthat are involved in a wide variety of processes, most notably as crucial elements for normal development
135
Define functional redundancy
when one gene can compensate for the loss of a related one
136
Define gastrula
an embryo at the stage following the blastula, when it is a hollow cup-shaped structure having three layers of cells (endoderm, mesoderm and ectoderm)
137
Define gastrulation
a phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a multilayered structure known as the gastrula
138
Define growth factors
molecules that typically act as signaling molecules between cells. Examples are cytokines and hormones that bind to specific receptors on the surface of their target cells. They often promote cell differentiation and maturation, which varies between growth factors
139
Define hedgehog
a type of morphogen that specifies anterior-posterior patterning in the limbs. It acts as a ligand in a signaling pathway that transmits information to embryonic cells required for proper cell differentiation
140
Define histology
the study of the microscopic structure of tissues
141
Define homeodomain
the part of the protein that attaches (binds) to specific regulatory regions of the target genes. Genes in the homeobox family are involved in a wide range of critical activities during development
142
Define homeotic transformation
when a body part develops as a different body part (i.e. a body part is in the wrong location)
143
Define hox cluster
a series of four clusters of Homeobox genes in mammals that play a key role in patterning the head-to -tail segmentation of the body
144
Define hox genes
a subset of homeotic genes, are a group of related genes that control the body plan of an embryo along the head-tail axis
145
Define hypoblast
a tissue type that forms from the inner cell mass. It lies beneath the epiblast and consists of small cuboidal cells. Extraembryonic endoderm (including Yolk sac) is derived from hypoblast cells.
146
Define immunofluorescence
a technique is used for light microscopy with a fluorescence microscope and is used primarily on microbiological sample. This technique uses the specificity of antibodies to their antigen to target fluorescent dyes to specific biomolecule targets within a cell, and therefore allows visualization of the distribution of the target molecule through the sample
147
Define induced pluripotent stem cells
cells derived from differentiated adult cells that have been induced back to stem cells by reprogramming with certain factors
148
Define induction
a change in cell fate due to signals sent from other cells
149
Define in situ hybridisation
a type of hybridization that uses a labeled complementary DNA, RNA or modified nucleic acids strand (i.e., probe) to localize a specific DNA or RNA sequence in a portion or section of tissue (in situ)
150
Define inner cell mass
a group of cells on one side of the blastocyst that will eventually give rise to the definitive structure of the foetus
151
Define inside-out hypothesis
states that the location of the cell in the morula determines its location and hence function in the blastocyst
152
Define lateral inhibition
when cells send inhibitory signals to neighbouring cells that alters their behaviour
153
Define lineage tracing
labelling a group of cells and seeing where they end up
154
Define mesenchymal cells
fusiform or stellate cells located between the ectoderm and endoderm of young embryos; the shape of the cells in fixed material is indicative of the fact that in life they were moving from their place of origin to areas where they would become reaggregated and specialized
155
Define mesenchymal stem cells (MSCs)
a type of multipotent adult stem cell that is found in various adult tissues that is linked to normal growth and repair in the body. It can differentiate into bone, cartilage or muscle depending on cues
156
Define mesoderm
the middle of the three germ layers, or masses of cells (lying between the ectoderm and endoderm), which appears early in the development of an animal embryo.
157
Define morphogen
a secreted, diffusible molecule that can influence fate of a field of neighbouring cells via a concentration gradient
158
Define morphogenesis
the organisation of form; groups of similar cells that have formed tissues organise with other tissues into specific shapes and sizes
159
Define morula
an early stage embryo consisting of cells (called blastomeres) in a solid ball contained within the zona pellucida
160
Define multipotent
having the ability to differentiate to a limited number of cell fates or into closely related family of cells
161
Define Nanog
a transcription factor critically involved with self-renewal of undifferentiated embryonic stem cells
162
Define neural crest
bilaterally paired strips of cells arising in the ectoderm at the margins of the neural tube. These cells migrate to many different locations and differentiate into many cell types within the embryo
163
Define neural tube
the future brain and spinal cord that forms from an area of ectoderm called the neural plate by a process called neurulation
164
Define neuralation
the folding process in vertebrate embryos, which includes the transformation of the neural plate into the neural tube. The embryo at this stage is termed the neurula
165
Define Notch signalling pathway
a highly conserved cell signaling system present in most multicellular organisms. Notch signaling promotes proliferative signaling during neurogenesis, and its activity is inhibited by Numb to promote neural differentiation. It plays a major role in the regulation of embryonic development
166
Define notochord
a solid rod of tissue derived from mesoderm that supports the embryo. It degenerates in mammals but it does send inductive signals to neighbouring ectoderm to form the neural tube
167
Define null mutants
A null mutation is a change in genetic sequence that can cause the complete loss of the protein encoded by the gene either by failing to transcribe it to RNA, or by an inability to translate the RNA sequence to protein
168
Define Oct4
a transcription factors that is critically involved in the self-renewal of undifferentiated embryonic stem cells.
169
Define organogenesis
the phase of embryonic development that starts at the end of gastrulation and goes until birth. During organogenesis, the three germ layers formed from gastrulation: the ectoderm, endoderm, and mesoderm form the internal organs of the organism
170
Define paracrine
denoting a type of hormone function in which hormone synthesized in and released from endocrine cells binds to its receptor in nearby cells and affects their function
171
Define paralogues
either of a pair of genes that derives from the same ancestral gene
172
Define pattern formation
the generation of complex organizations of cell fates in space and time. Pattern formation is controlled by genes
173
Define pluripotent
capable of giving rise to several different cell types
174
Define primitive streak
a structure that forms in the blastula during the early stages of avian, reptilian and mammalian embryonic development. It forms on the dorsal (back) face of the developing embryo, toward the caudal or posterior end.
175
Define qRT-PCR
a technique commonly used in molecular biology to qualitatively detect gene expression through the creation of complementary DNA (cDNA) transcripts from RNA
176
Define receptor tyrosine kinase (RTK)
high-affinity cell surface receptors for many polypeptide growth factors, cytokines, and hormones
177
Define reproductive cloning
the creation of an organism who has identical nuclear genetic material (DNA) to an existing member of the species, and who is allowed to develop to term and beyond
178
Define serine/threonine kinase receptor
a transmembrane receptor that contains serine/threonine kinase domain that recognises transforming growth factor-β
179
Define Smad proteins
a family of structurally similar proteins that are the main signal transducers for receptors of the transforming growth factor beta (TGF-B) superfamily, which are critically important for regulating cell development and growth
180
Define somatic cell nuclear transfer (SCNT)
a laboratory technique for replacing the nucleus of an ovum with that from a somatic cell
181
Define Sox2
a transcription factor that is essential for maintaining self-renewal, or pluripotency, of undifferentiated embryonic stem cells. Sox2 has a critical role in maintenance of embryonic and neural stem cells
182
Define spemann organiser
a cluster of cells in the developing embryo of an amphibian that induces development of the central nervous system.
183
Define stem cells
an undifferentiated cell that can self-renew and has the ability to differentiate into tissue- or organ-specific cell types
184
Define teratoma
a tumor made up of several different types of tissue, such as hair, muscle, or bone
185
Define therapeutic cloning
cloning designed as therapy for a disease. In therapeutic cloning, the nucleus of a cell, typically a skin cell, is inserted into a fertilized egg whose nucleus has been removed. The nucleated egg begins to divide repeatedly to form a blastocyst.
186
Define totipotent
capable of giving rise to any cell type or (of a blastomere) a complete embryo.
187
Define tranactivation domain
a transcription factor scaffold domain which contains binding sites for other proteins such as transcription coregulators
188
Define transcription factors
DNA-binding proteins that regulate the expression of an array of target gene that usually have transactivation domains that activate or repress genes)
189
Define transforming growth factor-β
a multifunctional cytokine that acts as a ligand for serine/threonine kinase complex
190
Define trophoblast
cells forming the outer layer of a blastocyst, which provide nutrients to the embryo and develop into a large part of the placenta
191
Define unipotent
capable of giving rise to only one cell type
192
Define western blotting
an important technique that detects specific proteins from a complex mixture of proteins extracted from cells. The techniques uses three elements to accomplish this task: (1) separation by size, (2) transfer to a solid support, and (3) marking target protein using a proper primary and secondary antibody to visualize
193
Define Wnt
a diverse family of secreted lipid-modified signalling glycoproteins that act as ligands to activates the Wnt pathways via paracrine and autocrine routes
194
A transcription factor protein is detectable in the nuclei of both the epithelial layer and in underlying mesenchymal cells. However, the factor only has an effect in the epithelial cells. this is best explained by:
Select one:
a. The gene is only present in the epithelial layer
b. The gene encoding the transcription factor is not expressed in mesenchymal cells
c. The factor relies on another factor for its activity that is only expressed in epithelial cells
d. The factor binds to a cell surface receptor that in only present in epithelial cells
c. The factor relies on another factor for its activity that is only expressed in epithelial cells
195
Which of the following steps would not be part of a procedure to produce a mouse over-expressing growth hormone?
Select one:
a. breeding chimeric mice with wild type mice
b. pronuclear injection
c. culturing ES cells
d. deletion of one allele by homologous recombination
d. deletion of one allele by homologous recombination
196
Which of the following statements is FALSE?
Select one:
a. Integrins bind a cell to the extracellular matrix
b. The epiblast is pluripotent
c. Sonic Hedgehog is an example of a morphogen
d. The trophoblast is displaced by the definitive endoderm
d. The trophoblast is displaced by the definitive endoderm
197
Which statement is CORRECT?
Select one:
a. When Wnt binds to its cell surface receptor, it leads to degradation of beta-catenin in the cell
b. Hedgehog signaling involves the Patched Receptor
c. Delta that is secreted from the cell can bind to Notch, an example of paracrine signaling
d. BMPs signal through is a Tyrosine kinase receptor
b. Hedgehog signaling involves the Patched Receptor
198
Vertebrate embryos show regulative ability, which means
Select one:
a. They can generate non-identical twins during embryonic development
b. They can produce normal tissues when cells are removed
c. They undergo gastrulation following blastocyst formation
d. Transcription factor genes can turn on or off their downstream targets
b. They can produce normal tissues when cells are removed
199
Which statement is FALSE?
Select one:
a. the anterior visceral endoderm (AVE) is required for organising the anterior-posterior axis
b. Wnt and Fgf signals help establish the posterior part of the early embryo
c. the primitive streak is required for gastrulation
d. The AVE forms in the epiblast opposite the primitive streak
d. The AVE forms in the epiblast opposite the primitive streak
200
You are given a tube of cells labeled “iPS cells”. Which of the following experiments would suggest that they are indeed iPS cells?
Select one:
a. they cannot self-renew
b. they can form a teratoma when injected into a mouse embryo
c. they can differentiate into every cell type in vitro
d. they do not express Oct4
b. they can form a teratoma when injected into a mouse embryo
201
Which statement about adult stem cells is FALSE?
Select one:
a. they are derived from somatic cell nuclear transfer
b. they can self renew
c. they are typically multipotent
d. they are found in a stem cell niche
a. they are derived from somatic cell nuclear transfer
