GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Differentiation

Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology

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Example Questions

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Example Question #1 : Differentiation

The mesodermal germ layer can give rise to each of the following cell types except __________.

Possible Answers:

myoblasts

fibroblasts

the notocord 

alveoli 

Correct answer:

alveoli 

Explanation:

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.

Example Question #1 : Help With Developmental Stages

Which of the listed processes are part of gastrulation?

Possible Answers:

The invagination of the notochord to induce the formation of the neural plate

The ingression of cells from the epiblast to form a circular blastocyst

The formation of ectoderm and endoderm germ layers in radially symmetric organisms

The formation of the primitive streak that undergoes epithelial to mesenchymal transition

Correct answer:

The formation of the primitive streak that undergoes epithelial to mesenchymal transition

Explanation:

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.

Example Question #1 : Differentiation

Which of the following statements about determination is true? 

Possible Answers:

The pattern of transcription is the same in a differentiated cell as it is in a determined cell 

Determination occurs after two cell divisions in most organisms

Determination follows differentiation

No matter where its placed in an embryo, a determined cell will keep its determination

Once determined, a cell changes its appearance

Correct answer:

No matter where its placed in an embryo, a determined cell will keep its determination

Explanation:

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). 

Example Question #1 : Help With Developmental Stages

Which of the following terms describes when the single germ layered blastula reorganizes into a structure with mesoderm, endoderm, and ectoderm germ layers? 

Possible Answers:

Gastrulation

Myogenesis

Blastulation

Somiteogenesis

Morphogenesis

Correct answer:

Gastrulation

Explanation:

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. 

Example Question #333 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

Which embryonic structure is created by the process of gastrulation?

Possible Answers:

The mesoderm

The epiblast

The notochord

The neural tube

Correct answer:

The mesoderm

Explanation:

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.

Example Question #131 : Cell Biology

How do master regulators, which are transcription factors, establish cell subtypes and cell subtype-specific gene expression? 

Possible Answers:

Master regulators bind promoters by not enhancers to initiate specific gene expression

Master regulators promote active promoter formation by deposition of methyl groups 

Master regulators promote the deposition of methyl or acetyl groups to mark inactive or active enhancers 

Master regulators always promote formation of euchromatin in nucleosome dense regions 

None of the other answers

Correct answer:

Master regulators promote the deposition of methyl or acetyl groups to mark inactive or active enhancers 

Explanation:

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. 

Example Question #1 : Help With Developmental Genes

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?

Possible Answers:

Growth factor 

Receptor

Enzyme

Lipid

Morphogen 

Correct answer:

Morphogen 

Explanation:

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.

Example Question #341 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

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?

Possible Answers:

Head missing or malformed

Missing wing appendages

Genital structures missing

Extra legs extending from thorax

Extra wing appendages

Correct answer:

Head missing or malformed

Explanation:

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.

Example Question #71 : Cellular Processes

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?

Possible Answers:

Golgi-endoplasmic reticulum trafficking proteins

Structural proteins 

Transmembrane receptors 

Mitochondrial proteins

Transcription factors

Correct answer:

Transcription factors

Explanation:

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. 

Example Question #141 : Cell Biology

Which of the following is an example of a multipotent stem cell differentiation into a terminal cell type?

Possible Answers:

Bone marrow cells giving rise to lymphosites

Endoderm cells giving rise to enterocytes

iPS cells giving rise to cardiomyocytes

A zygote giving rise to germ layers

Correct answer:

Bone marrow cells giving rise to lymphosites

Explanation:

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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