Differentiation - GRE Subject Test: Biochemistry, Cell, and Molecular Biology
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RNA of Gene X was injected into the posterior of a fruit fly embryo, and the resulting embryo had two heads instead of a head and a tail. What type of protein does gene X most likely code for?
RNA of Gene X was injected into the posterior of a fruit fly embryo, and the resulting embryo had two heads instead of a head and a tail. What type of protein does gene X most likely code for?
Morphogens are proteins that can regulate the patterning of embryos over a multi-cell distance. Classic morphogens were discovered by injecting cytoplasm of embryos from the anteiror to the posterior, which would give rise to an animal with two heads. Injecting cytoplasm from the posterior to the anterior would give rise to animals with two posteriors. If injecting the RNA of a particular gene changes the patterning of the animal dramatically, it is likely a morphogen.
Morphogens are proteins that can regulate the patterning of embryos over a multi-cell distance. Classic morphogens were discovered by injecting cytoplasm of embryos from the anteiror to the posterior, which would give rise to an animal with two heads. Injecting cytoplasm from the posterior to the anterior would give rise to animals with two posteriors. If injecting the RNA of a particular gene changes the patterning of the animal dramatically, it is likely a morphogen.
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Homeobox (Hox) genes are essential regulators of development of an organism, as they define region specific development of an embryo along its anterior-posterioir axis. A mutation in the gene Antennapedia, for example, causes Drosophila melanogaster to grow legs from its head instead of antennae.
Given that hox genes regulate segmental identity of an organism, which of the following phenotypes would possibly be present in a fruit fly with a mutation in a Hox gene required for formation of very anterior structures?
Homeobox (Hox) genes are essential regulators of development of an organism, as they define region specific development of an embryo along its anterior-posterioir axis. A mutation in the gene Antennapedia, for example, causes Drosophila melanogaster to grow legs from its head instead of antennae.
Given that hox genes regulate segmental identity of an organism, which of the following phenotypes would possibly be present in a fruit fly with a mutation in a Hox gene required for formation of very anterior structures?
The only 'very anterior' structure listed among the answers is the head. If this particular hox gene is required to create the proper anterior appendage, we can predict that of the structures listed the head is most likely to be affected.
The only 'very anterior' structure listed among the answers is the head. If this particular hox gene is required to create the proper anterior appendage, we can predict that of the structures listed the head is most likely to be affected.
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HOX genes are a group of genes that have been well characterized to control body plan development along the anterior to posterior axis in developing embryos. What do HOX genes encode?
HOX genes are a group of genes that have been well characterized to control body plan development along the anterior to posterior axis in developing embryos. What do HOX genes encode?
The correct answer is transcription factors. HOX transcription factors turn on genes during embryonic development to determine the type of segment structure (examples are legs or antennae) at different spatial regions of the embryo. Absence or mis-expression of HOX genes in early development renders misinformed or non-viable organisms.
The correct answer is transcription factors. HOX transcription factors turn on genes during embryonic development to determine the type of segment structure (examples are legs or antennae) at different spatial regions of the embryo. Absence or mis-expression of HOX genes in early development renders misinformed or non-viable organisms.
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How do master regulators, which are transcription factors, establish cell subtypes and cell subtype-specific gene expression?
How do master regulators, which are transcription factors, establish cell subtypes and cell subtype-specific gene expression?
The correct answer is master regulators promote the deposition of methyl or acetyl groups to mark inactive or active enhancers. Master regulators bind enhancer regions that have been created by pioneer factors to establish the chromatin state of the cell by deposition of methyl or acetyl groups on chromatin. Methylation correlates with inactive enhancers, whereas acetylation correlates with active enhancers. The fingerprint of active/inactive enhancers and its effect on gene expression establishes cell subtypes. Some, but not all master regulators function as pioneer factors to bind nucleosome rich DNA to promote euchromatin formation.
The correct answer is master regulators promote the deposition of methyl or acetyl groups to mark inactive or active enhancers. Master regulators bind enhancer regions that have been created by pioneer factors to establish the chromatin state of the cell by deposition of methyl or acetyl groups on chromatin. Methylation correlates with inactive enhancers, whereas acetylation correlates with active enhancers. The fingerprint of active/inactive enhancers and its effect on gene expression establishes cell subtypes. Some, but not all master regulators function as pioneer factors to bind nucleosome rich DNA to promote euchromatin formation.
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The mesodermal germ layer can give rise to each of the following cell types except __________.
The mesodermal germ layer can give rise to each of the following cell types except __________.
The mesoderm gives rise to the "middle" cells that line the body, such as the muscle. The notocord is a critical embryonic structure that forms from the mesoderm, and myoblasts and fibroblasts are cells that line the body. The alveoli are part of the lung, which originates from the endodermal germ layer.
The mesoderm gives rise to the "middle" cells that line the body, such as the muscle. The notocord is a critical embryonic structure that forms from the mesoderm, and myoblasts and fibroblasts are cells that line the body. The alveoli are part of the lung, which originates from the endodermal germ layer.
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Which of the listed processes are part of gastrulation?
Which of the listed processes are part of gastrulation?
Gastrulation is the process of cells from the epiblast ingressing into the embryo to form the three germ layers of bilaterally symetrical animals. When gastrulation is complete, the embryo is referred to as a gastrula. The group of cells that lead the migration of cells into the embryo are called the primitive streak, and they undergo epithelial to mesenchymal transition to be able to migrate. You can image the epithelium as many tightly packed squares. Becomimg mesenchymal turns these cells into more malleable stage, like a soft cushion. They can then "drop" into the inner layer of the blastocyst and lead the process of gastrulation.
Gastrulation is the process of cells from the epiblast ingressing into the embryo to form the three germ layers of bilaterally symetrical animals. When gastrulation is complete, the embryo is referred to as a gastrula. The group of cells that lead the migration of cells into the embryo are called the primitive streak, and they undergo epithelial to mesenchymal transition to be able to migrate. You can image the epithelium as many tightly packed squares. Becomimg mesenchymal turns these cells into more malleable stage, like a soft cushion. They can then "drop" into the inner layer of the blastocyst and lead the process of gastrulation.
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Which of the following statements about determination is true?
Which of the following statements about determination is true?
Determination is the process of a cell committing to a particular fate and is influenced by the cell's environment as well as its own genome. It's not possible to tell the difference between an undetermined and a determined cell since determined cells do not change in appearance. After determination comes differentiation. Differentiation results from differential gene expression (transcription, mRNA splicing, and translation).
Determination is the process of a cell committing to a particular fate and is influenced by the cell's environment as well as its own genome. It's not possible to tell the difference between an undetermined and a determined cell since determined cells do not change in appearance. After determination comes differentiation. Differentiation results from differential gene expression (transcription, mRNA splicing, and translation).
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Which of the following terms describes when the single germ layered blastula reorganizes into a structure with mesoderm, endoderm, and ectoderm germ layers?
Which of the following terms describes when the single germ layered blastula reorganizes into a structure with mesoderm, endoderm, and ectoderm germ layers?
The correct answer is gastrulation. Gastrulation occurs through five stages (1. invagination 2. involution 3. ingression 4. delamination 5. epiboly) and results in the formation of a gastrula with the mesoderm, endoderm, and ectoderm germ layers. Blastulation is the formation of the single germ layered blastula, which is a process that precedes gastrulation. Somiteogenesis forms somites in developing embryos to give rise to the future spine. Myogenesis is the formation of muscle tissue. Morphogenesis is the process of an organism forming its shape, driven by cell cycle progression, differentiation, and subsequent development of organs and appendages.
The correct answer is gastrulation. Gastrulation occurs through five stages (1. invagination 2. involution 3. ingression 4. delamination 5. epiboly) and results in the formation of a gastrula with the mesoderm, endoderm, and ectoderm germ layers. Blastulation is the formation of the single germ layered blastula, which is a process that precedes gastrulation. Somiteogenesis forms somites in developing embryos to give rise to the future spine. Myogenesis is the formation of muscle tissue. Morphogenesis is the process of an organism forming its shape, driven by cell cycle progression, differentiation, and subsequent development of organs and appendages.
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Which embryonic structure is created by the process of gastrulation?
Which embryonic structure is created by the process of gastrulation?
Gastrulation is a process occurring in week three of development. At this time, the epiblast will further differentiate into three germ layers: the ectoderm, the mesoderm, and the endoderm. As a result, we can say that gastrulation allows for the creation of the mesoderm.
Gastrulation is a process occurring in week three of development. At this time, the epiblast will further differentiate into three germ layers: the ectoderm, the mesoderm, and the endoderm. As a result, we can say that gastrulation allows for the creation of the mesoderm.
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Which of the following mutations in the EGF pathway could lead to increased proliferation of cells?
Which of the following mutations in the EGF pathway could lead to increased proliferation of cells?
The phosphorylation of Erk is the final step of the protein cascade of EGF pathway, and phosphorylated Erk enters the nucleus to increase transcription of genes that induce proliferation. If Erk is constitutively active, it will likely lead to higher proliferation rate.
Preventing EGF from binding to EGFR or disrupting EGFR's ability to enter the membrane would abolish EGF pathway activity and reduce proliferation. Likewise, abolishing kinase activity of RAF would terminate the signal transduction and lead to reduced proliferation.
The phosphorylation of Erk is the final step of the protein cascade of EGF pathway, and phosphorylated Erk enters the nucleus to increase transcription of genes that induce proliferation. If Erk is constitutively active, it will likely lead to higher proliferation rate.
Preventing EGF from binding to EGFR or disrupting EGFR's ability to enter the membrane would abolish EGF pathway activity and reduce proliferation. Likewise, abolishing kinase activity of RAF would terminate the signal transduction and lead to reduced proliferation.
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Production of which of the following cytokines is stimulated when the 
concentration decreases in the circulatory system?
Production of which of the following cytokines is stimulated when the
Erythropoietin, released by the kidney, stimulates the production of red blood cells, which becomes necessary if circulating 
has decreased. Tumor necrosis factor stimulates systemic inflammation and regulates the immune system. Transforming growth factor beta 1 controls cell growth, proliferation, differentiation and other processes. Interferon type II modulates immune functions. Interleukin 2 also modulates the immune cells.
Erythropoietin, released by the kidney, stimulates the production of red blood cells, which becomes necessary if circulating
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Which of the following growth factors is primarily produced by the kidney and is essential for the production of red blood cells?
Which of the following growth factors is primarily produced by the kidney and is essential for the production of red blood cells?
Erythropoietin is a glycoprotein that is crucial for the production of red blood cells, a process also called "erythropoiesis." Each of the other answers contains a growth factor, but none of these have a primary function in red blood cell production.
Erythropoietin is a glycoprotein that is crucial for the production of red blood cells, a process also called "erythropoiesis." Each of the other answers contains a growth factor, but none of these have a primary function in red blood cell production.
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Which of the following cells is not correctly matched to the proper classification of cell (permanent, stable, labile)?
Which of the following cells is not correctly matched to the proper classification of cell (permanent, stable, labile)?
Permanent cells remain in G0 and do not divide. They regenerate from stem cells, but cannot undergo division themselves. Neurons, skeletal muscle, cardiac muscle, and red blood cells are permanent cells.
Stable (quiescent) cells enter G1 from G0 when stimulated by introduction of the protein cyclin. Hepatocytes and lymphocytes are examples of stable cells.
Labile cells never go into G0 and divide rapidly with a short G1. Bone marrow, gut epithelium, skin, and hair follicles are examples of labile cells.
Permanent cells remain in G0 and do not divide. They regenerate from stem cells, but cannot undergo division themselves. Neurons, skeletal muscle, cardiac muscle, and red blood cells are permanent cells.
Stable (quiescent) cells enter G1 from G0 when stimulated by introduction of the protein cyclin. Hepatocytes and lymphocytes are examples of stable cells.
Labile cells never go into G0 and divide rapidly with a short G1. Bone marrow, gut epithelium, skin, and hair follicles are examples of labile cells.
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Activation of the notch receptor by its ligand, delta, in neighboring cell populations defines patterns of distinct differentiated cell types among cells that have the potential to adopt the same fate. What is this process known as?
Activation of the notch receptor by its ligand, delta, in neighboring cell populations defines patterns of distinct differentiated cell types among cells that have the potential to adopt the same fate. What is this process known as?
The correct answer is lateral inhibition. Also known as lateral specification, is a process that defines distinct cell types. This process is particularly important in vertebrate embryo nervous system development. Notch signaling is important for many developmental processes. Typically, lateral inhibition involves signaling through the notch receptor, which is stimulated by neighbor cells expressing the notch ligand, delta. Given that only neighboring cells can activate this signaling pathway, defined neighborhoods of undergo differentiation to become a distinct cell type. Morphollaxis is a term that describes regeneration of limbs without cell proliferation. Delamination describes mitotically dividing cells that split one cellular layer into two parallel layers. Furthermore, in terms of development, invagination is the initial step of gastrulation that reorganizes the embryo into a multi-layered organism with a body cavity.
The correct answer is lateral inhibition. Also known as lateral specification, is a process that defines distinct cell types. This process is particularly important in vertebrate embryo nervous system development. Notch signaling is important for many developmental processes. Typically, lateral inhibition involves signaling through the notch receptor, which is stimulated by neighbor cells expressing the notch ligand, delta. Given that only neighboring cells can activate this signaling pathway, defined neighborhoods of undergo differentiation to become a distinct cell type. Morphollaxis is a term that describes regeneration of limbs without cell proliferation. Delamination describes mitotically dividing cells that split one cellular layer into two parallel layers. Furthermore, in terms of development, invagination is the initial step of gastrulation that reorganizes the embryo into a multi-layered organism with a body cavity.
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Which term best describes when a cell has two stable equilibrium states, but can only exist in one state at a time? States are often phenotypes.
Which term best describes when a cell has two stable equilibrium states, but can only exist in one state at a time? States are often phenotypes.
The correct answer is bistability. Bistability is a phenomenon that is observed in signaling pathways and cell commitment to one cell fate over another cell fate by differentiation, however, either cell fate is equally likely. Lateral inhibition occurs when cells signal to neighboring cells to effect a physiological change. Quiescence is a resting, non-dividing cell state. Hysteresis is the retention of a cell-state due to feedback signaling even in the absence of the initial stimulus.
The correct answer is bistability. Bistability is a phenomenon that is observed in signaling pathways and cell commitment to one cell fate over another cell fate by differentiation, however, either cell fate is equally likely. Lateral inhibition occurs when cells signal to neighboring cells to effect a physiological change. Quiescence is a resting, non-dividing cell state. Hysteresis is the retention of a cell-state due to feedback signaling even in the absence of the initial stimulus.
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Which of the following is an example of a multipotent stem cell differentiation into a terminal cell type?
Which of the following is an example of a multipotent stem cell differentiation into a terminal cell type?
Multipotent cell types can give rise to a small number of cell types but have a restricted fate. This is in contrast to totipotent (zygote) or pluripotent cells (germ layers, iPS (induced pluripotent cells)) which can give rise to many different cell types, some that may make up very different parts of the body.
Multipotent cell types can give rise to a small number of cell types but have a restricted fate. This is in contrast to totipotent (zygote) or pluripotent cells (germ layers, iPS (induced pluripotent cells)) which can give rise to many different cell types, some that may make up very different parts of the body.
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During asymmetric cell division, cells divide such that the mitotic spindles are oriented perpendicular to the plane on which the cells reside. What types of cells are the original parent cells and how does this affect cell lineage?
During asymmetric cell division, cells divide such that the mitotic spindles are oriented perpendicular to the plane on which the cells reside. What types of cells are the original parent cells and how does this affect cell lineage?
The correct answer is that asymmetric cell division begins the differentiation process from "parent" stem cells. Symmetric cell division generates two identical daughter cells that have mitotic spindles oriented parallel to the plane on which the cells reside. However, cells that begin a differentiation lineage undergo asymmetric cell division. The perpendicularity of the mitotic spindle in cells that eventually differentiate contributes to this process.
The correct answer is that asymmetric cell division begins the differentiation process from "parent" stem cells. Symmetric cell division generates two identical daughter cells that have mitotic spindles oriented parallel to the plane on which the cells reside. However, cells that begin a differentiation lineage undergo asymmetric cell division. The perpendicularity of the mitotic spindle in cells that eventually differentiate contributes to this process.
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Which is the following answers best describes the key difference between totipotentand pluripotentstem cells?
Which is the following answers best describes the key difference between totipotentand pluripotentstem cells?
Totipotent stem cells are the stem cells with the greatest potential of all stem cell types. A totipotent stem cell can give rise to any embryonic cell type, and can ultimately form an entire organism. Pluripotent stem cells can become any of the three embryonic germ layers, however, they do not have the capacity to form an entire organism because they cannot give rise to the extraembryonic tissue required for development, such as the placenta.
Totipotent stem cells are the stem cells with the greatest potential of all stem cell types. A totipotent stem cell can give rise to any embryonic cell type, and can ultimately form an entire organism. Pluripotent stem cells can become any of the three embryonic germ layers, however, they do not have the capacity to form an entire organism because they cannot give rise to the extraembryonic tissue required for development, such as the placenta.
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