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

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

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All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

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Example Questions

Example Question #71 :Gre Subject Test: Biochemistry, Cell, And Molecular Biology

What technique allows scientists to measure gene expression via probe-cDNA hybridization fluorescent intensity?

Possible Answers:

Immunohistochemistry

Karyotype

Fluorescence-activated cell sorting (FACS)

In situ hybridization (ISH)

DNA microarray

Correct answer:

DNA microarray

Explanation:

The correct answer is DNA microarray. In a DNA microarray, short DNA sequences (probes) are labelled on a microarray chip. Probes for the same gene are clustered in the same area on the array. cDNA from a sample is labelled with a fluorescent dye and washed over the chip. If a certain gene is more highly expressed, its cDNA will bind the respective probes and give a higher intensity than a lower expressed gene.

Example Question #3 :Help With Other Laboratory Techniques

A student researcher performs indirect immunofluorescence of mammalian cells for a transmembrane protein with an antibody to the C-terminus of the protein. First, the student researcher does not permeabilize cells' plasma membranes and stains with the protein specific antibody. Secondly, the researcher permeabilizes the cells' plasma membranes and stains with the protein specific antibody.

What is the student researcher trying to determine with these two experiments?

Possible Answers:

Whether the C-terminus of the protein is extracellular or intracellular

Whether the protein localization is disrupted when the plasma membrane is permeabilized

If the protein is localized to the Golgi apparatus

Whether the cells can survive permeabilization

If the protein is localized to the Golgi apparatus

Correct answer:

Whether the C-terminus of the protein is extracellular or intracellular

Explanation:

The correct answer is whether the C-terminus of the protein is extracellular or intracellular. This is a very common laboratory technique to determine which terminus of a transmembrane protein is intracellular and extracellular. Since the antibody is specific to the C-terminus of the protein and if the C-terminus of the protein is intracellularly localized, we will only be able to detect the protein if the cells are permeabilized. In cells that are not permeabilized, the antibody will not be able to enter the cells, but permeabilization will allow the antibody to pass through the plasma membrane and bind the C-terminus. If the C-terminus is extracellular, the antibody will bind regardless of permeabilization.

Example Question #72 :Gre Subject Test: Biochemistry, Cell, And Molecular Biology

Which of the following is not a valid method to introduce exogenous DNA into a cell?

Possible Answers:

Infection

Transfection

Electroporation

Transformation

None of these

Correct answer:

None of these

Explanation:

All of the given answers are valid methods to introduce exogenous DNA into a cell. When working with bacteria, transformations are a simple way to introduce plasmid DNA into the cell by chemical competency. Electroporation electrocutes both bacterial and cell culture cells to introduce exogenous DNA. Infection of target cells may also be a viable method if the laboratory is equipped to generate live virus containing exogenous DNA to be introduced. Finally, transfection refers to a process mainly reserved for cell culture that introduces exogenous DNA through liposome fusion (containing DNA) with cell membranes.

Example Question #73 :Gre Subject Test: Biochemistry, Cell, And Molecular Biology

Work on theAnophelesmosquito attempting to study the blood digestion process found that over 2,000 genes were upregulated and downregulated through digestion. What technology makes it possible to study expression levels of large number of genes like this?

Possible Answers:

Next generation DNA sequencing

Sanger DNA sequencing

DNA microarrays

None of these

Polymerase chain reaction

Correct answer:

DNA microarrays

Explanation:

Microarrays allow for the study of expression levels of thousands of genes simultaneously. Although microarrays do not tell you anything about the actual sequence of the genes, they are the only option for studying the expression levels of massive numbers of genes. It is possible to study expression levels using PCR, but not on a large scale.

Example Question #74 :Gre Subject Test: Biochemistry, Cell, And Molecular Biology

What was the early technique used in molecular genetics to study "alleles" of various enzymes?

Possible Answers:

Isoenzymatic gels

Allozyme gels

None of these

Isozyme gels

Northern blots

Correct answer:

Allozyme gels

Explanation:

Running allozyme gels was one of the first methods used in molecular studies of these enzymes that have slightly different functions due to having slightly different genetic codes (alleles). This term refers specifically to enzymatic variation created by genetic variation/alleles.

Example Question #75 :Gre Subject Test: Biochemistry, Cell, And Molecular Biology

What is the purpose of a phenol/chloroform extraction?

Possible Answers:

To separate DNA and RNA from proteins

To separate euchromatin from heterochromatin in cell lysates

To generate a protein lysate from tissue culture cells by lysing

None of the other answers

To separate proteins and other impurities from DNA or RNA

Correct answer:

To separate proteins and other impurities from DNA or RNA

Explanation:

The correct answer is to separate proteins and other impurities from DNA or RNA. An extraction by phenol followed by chloroform will separate proteins and other impurities from DNA and RNA (in suspended fraction). Next, depending on the type and concentration of salt used, a researcher can selectively precipitate either DNA or RNA from the mixture with the addition of ethanol. This is a simple method to obtain pure clean ribonucleic acids from impure sources.

Example Question #76 :Gre Subject Test: Biochemistry, Cell, And Molecular Biology

Which of the following techniques most likely utilizes a detergent, such as sodium dodecyl sulfate?

Possible Answers:

None of the other answers

All of these require utilization of a detergent

Lysis of the plasma membrane

Purification of DNA from RNA and proteins

Separation of small and large ionic compounds

Correct answer:

Lysis of the plasma membrane

Explanation:

The correct answer is lysis of the plasma membrane. While detergents such as sodium dodecyl sulfate are commonly used in western blots as a protein denaturing agent, it also breaks down the plasma membrane by emulsifying membrane-bound lipids and proteins.

Example Question #1 :Biochemistry

Which of the following statements is not true regarding Gibbs free energy,?

Possible Answers:

If theof a reaction is zero, the reaction is at equilibrium

Theof a reaction is partially dependent on the temperature of the system

Theof a reaction is partially dependent on enthalpy of the system

If theof a reaction is less than zero, the reaction is endergonic

If theof a reaction is positive, the reaction is not favorable and likely requires external energy to proceed

Correct answer:

If theof a reaction is less than zero, the reaction is endergonic

Explanation:

If theof a reaction is less than zero, the reaction will in fact be exergonic. These reactions will be favorable and spontaneous, and energy isreleasedin these reactions. Thus, endergonic is incorrect.

Example Question #77 :Gre Subject Test: Biochemistry, Cell, And Molecular Biology

The equilibrium constantof any given chemical reaction is__________on the temperature and pressure of the reactants and products and is__________of the reaction rate.

Possible Answers:

dependent . . . dependent

Independent . . . one-half

dependent . . . one-half

dependent . . . independent

independent . . . dependent

Correct answer:

dependent . . . independent

Explanation:

The temperature and pressure of the reactants and products of any given reaction will determine the value of. However, this is entirely dependent of the reaction rate, which is determined by how the concentrations of the reactants and products change over the course of the reaction. Additionally, every reaction is unique, so "one-half" or any other exact metric cannot be applied as the definition.

Example Question #1 :Biochemistry

Which of the following best describes a reaction that has reached equilibrium?

Possible Answers:

is zero, and the forward reaction is occurring spontaneously.

is less than zero, and the forward and reverse reactions are occurring at equal rates.

is zero, and both the forward and reverse reactions have stopped occurring completely.

is zero, and the forward and reverse reactions are occurring at equal rates.

is greater than zero, and the forward and reverse reactions are occurring at equal rates.

Correct answer:

is zero, and the forward and reverse reactions are occurring at equal rates.

Explanation:

In equilibrium, both the forward and reverse reactions continue to occur, but they do so in a way that is equal and thus, there is no net change of reactants and products in the system.is zero in this case because net changes to the system have ceased, and thus the free energy is no longer in flux.

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