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

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

1 Diagnostic Test 201 Practice Tests Question of the Day Flashcards Learn by Concept

Example Questions

Example Question #11 : Help With Genetic Cloning, Splicing, And Sequencing

What makes next generation sequencing different from first generation sequencing (Sanger)?

Possible Answers:

Next generation sequencing increased DNA sequence output substantially

Next generation sequencing makes it much easier to create full genome data sets

First generation sequencing is capable of sequencing longer continuous strings of DNA (read length)

All of these

First generation sequencing requires prior knowledge of every DNA segment to be sequenced

Correct answer:

All of these

Explanation:

All of these answers are correct. Next generation sequencing substantially increased DNA sequence generation speed, and makes it much easier to assemble full genomes. Earlier, Sanger sequencing requires that you know a primer sequence for each fragment you'd like to sequence, but its read lengths are still longer than next generation sequencing methods, which rely on creation of many relatively short sequences.

Example Question #11 : Help With Genetic Cloning, Splicing, And Sequencing

What is directional cloning?

Possible Answers:

All of these

Two restriction enzymes are used to cut both the plasmid and the subject DNA to be incorporated

None of these

Use of alkaline phosphatase to create nicks in the ends of a cut plasmid, preventing ligation by ligase

A cloning reaction that uses a marker system like the lacZ marker to identify recombinant plasmids

Correct answer:

Two restriction enzymes are used to cut both the plasmid and the subject DNA to be incorporated

Explanation:

Directional cloning is the process by which two restriction enzymes cut the plasmid and the subject DNA, creating a situation in which the plasmid cannot recircularize because the only viable combination of linking is plasmid-subject DNA-plasmid.

Example Question #53 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

Lambda cloning remains one of the most efficient cloning methods available. What steps are required in the reaction with the lambda phage to clone and copy your subject DNA?

Possible Answers:

Subject DNA is annealed to sticky ends in the phage

All of these steps are necessary

The phage is specially engineered to insert DNA when it is a recombinant phage

None of these steps are necessary

A plate of bacteria is infected with the phage

Correct answer:

All of these steps are necessary

Explanation:

Cloning with the Lambda phage involves all of these basic steps. The subject DNA is annealed to sticky ends inside the phage DNA. A plate of bacteria is infected with the phage, which actually does the replication of your DNA. The phages are specifically engineered to only insert DNA into the bacteria for replication if it actually incorporated your DNA fragment.

Example Question #54 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

What is the main difference between second next-generation sequencing and third next-generation sequencing?

Possible Answers:

Second next-generation sequencing allows for only single-end reads, third next-generation sequencing allows for paired-end reads

Second next-generation sequencing requires amplification of DNA, but third next-generation sequencing can sequence single molecules

Second next-generation sequencing is for DNA, but third next-generation sequencing is for amino acid chains

Third next-generation sequencing requires amplification of DNA, but second next-generation sequencing can sequence single molecules

Second next-generation sequencing uses emulsion PCR to amplify DNA, third next-generation sequencing uses bridge PCR to amplify DNA 

Correct answer:

Second next-generation sequencing requires amplification of DNA, but third next-generation sequencing can sequence single molecules

Explanation:

The correct answer is second next-generation sequencing requires amplification of DNA, but third next-generation sequencing can sequence single molecules. This major advance in sequencing technology allows a researcher to only sequence the DNA present in a given cell, for example, with third generation sequencing. This reduces amplicon bias that can occur when amplifying DNA to prepare it for second generation sequencing, generating truly representative sequencing.

Example Question #15 : Help With Genetic Cloning, Splicing, And Sequencing

Why is targeted amplicon sequencing (TAS) a better tool to identify species in metagenomic studies than next-generation sequencing of genomic DNA?

Possible Answers:

Given the diversity of species in a metagenome, it is impossible to isolate genomic DNA from most species due to technical hurdles

Isolation of intact metagenomic DNA for whole genome sequencing is tedious and erroneous

None of the other answers

TAS amplifies conserved yet divergent genes, such as rRNA genes, to identify species. Many species do not have sequenced genomes. 

Current sequencing technologies can not perform whole metagenome sequencing 

Correct answer:

TAS amplifies conserved yet divergent genes, such as rRNA genes, to identify species. Many species do not have sequenced genomes. 

Explanation:

The correct answer is TAS amplifies conserved yet divergent genes, such as rRNA genes, to identify species. Many species do not have sequenced genomes. Metagenomic DNA isolation is performed regularly to survey microbial species in a given sample and can be sequenced by next-generation sequencing. However, identifying species based on whole genome sequencing is very difficult because we have not sequenced the genomes for most organisms. Furthermore, computationally aligning whole genomes to reference genomes is very tedious and time consuming. rRNA genes have highly conserved regions that allow researchers to design primers to anneal in almost every species. However, the highly divergent portions of rRNA genes allow for specie identification. TAS amplifies and sequences specific genes, such as rRNA genes, for specie identification studies.  

Example Question #55 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

What technology allows for the assembly of a large DNA sequence from many shorter template sequences by oligonucleotide primer driven polymerase amplification? 

Possible Answers:

Restriction endonuclease digestion 

DNA ligation 

Gibson assembly 

Polymerase chain reaction 

Polymerase cycling assembly 

Correct answer:

Polymerase cycling assembly 

Explanation:

The correct answer is polymerase cycling assembly. In this reaction, multiple template sequences are included into a reaction with primers to the 5' most and 3' most sequence of the desired final product. The template sequences must also have regions of homology overlap with each other such that upon denaturing and annealing they hybridize to form a larger fragment. Upon hybridization, the primers will promote polymerase amplification of one large product. 

Example Question #57 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

When making a fusion protein with an N-termial biochemical tag, where should start and stop codons be located within this sequence?  

Possible Answers:

The start codons should be 5' to the biochemical tag and between the tag and the protein of interest. The stop codon should be 3' to the protein of interest. 

The start codon should be 5' of the biochemical tag and the stop codon should be between the tag and the protein of interest. 

The start codon should be 5' to the biochemical tag and the stop codons should be between the tag and the protein of interest as well as 3' to the protein of interest. 

The start codon should be between the biochemical tag and the protein of interest. The stop codon should be 3' to the protein of interest. 

The start codon should be 5' to the biochemical tag and the stop codon should be 3' to the protein of interest. 

Correct answer:

The start codon should be 5' to the biochemical tag and the stop codon should be 3' to the protein of interest. 

Explanation:

The correct answer is the start codon should be 5' to the biochemical tag and the stop codon should be 3' to the protein of interest. When designing fusion proteins with N-terminal biochemical tags, it is important to remove the native start codon for the protein of interest to prevent initiation of transcription at multiple sites. A start codon is required immediately 5' to the biochemical tag to include the tag in the expression of the fusion protein. Only one stop codon is required at the end of the fusion protein sequence (3'). 

Example Question #56 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

A student researcher is trying to insert a gene of interest into a plasmid backbone by restriction enzyme cloning with two enzymes that blunt cut DNA. Why is this not advisable? 

Possible Answers:

This method is a completely viable way to insert a gene into a plasmid backbone

Two blunt cutting restriction enzymes cannot be used for cloning 

Once DNA has been blunt cut by a restriction enzyme, it cannot re-ligate

Blunt cutting via restriction enzymes ultimately adds extra basepairs to the insertion which can disrupt the reading frame

There is no control over the orientation of the insertion into the plasmid backbone

Correct answer:

There is no control over the orientation of the insertion into the plasmid backbone

Explanation:

The correct answer is that there is no control over the orientation of the insertion into the plasmid backbone. Since there are no single stranded base pair overhangs that normally occur with restriction enzyme digestion in a blunt cutter digestion, the insertion (with blunt ends) will ligate with the plasmid backbone (with blunt ends) in both orientations randomly. This creates a grave difficulty in analyzing clones to make sure the gene insertion is in the correct orientation. 

Example Question #59 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

During a bacterial transformation of a plasmid, what is the purpose of incubating the bacteria with calcium chloride in the experiment? 

Possible Answers:

Calcium chloride surrounds the bacterial membrane and attracts negatively charged DNA

Calcium chloride facilitates plasma membrane restructuring following passage of genetic material into the cell 

Calcium chloride promotes bacterial colony growth on agar plates following transformation

Calcium chloride mechanically permeates the plasma membrane to allow in genetic material 

None of the other answers

Correct answer:

Calcium chloride surrounds the bacterial membrane and attracts negatively charged DNA

Explanation:

The correct answer is calcium chloride surrounds the bacterial membrane and attracts negatively charged DNA. Plasmid DNA is introduced to calcium chloride incubated bacteria and are mixed at  for up to one hour. Then, a heat shock to  causes the plasma membrane to loosen, allowing the plasmid DNA to enter the cells. A recovery period in nutrient broth at  promotes plasma membrane recovery and initiation of bacterial replication.  

Example Question #12 : Help With Genetic Cloning, Splicing, And Sequencing

During a bacterial transformation, why do you recover transformed bacteria in luria broth at  following heat shock instead of directly plating bacteria on agar containing antibiotics? 

Possible Answers:

The transformed bacteria need time to transcribe and translate the antibiotic resistant gene on the plasmid 

The high concentration of calcium chloride in the transformation mixture needs to be diluted out to prevent lethality

Bacteria only commence replication in liquid media and not agar media 

 is too warm for bacterial growth

None of the other answers

Correct answer:

The transformed bacteria need time to transcribe and translate the antibiotic resistant gene on the plasmid 

Explanation:

The correct answer is that the transformed bacteria need time to transcribe and translate the antibiotic resistant gene on the plasmid. Bacteria used in transformations do not inherently contain antibiotic resistance genes. The genes that confer antibiotic resistance for bacteria often come from exogenous plasmids introduced by techniques such as transformations. There is a lag in expression of these plasmids, and as such, the transformed bacteria will not be immediately antibiotic resistant following introduction of the plasmid.  

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

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