All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
Example Questions
Example Question #51 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology
What makes next generation sequencing different from first generation sequencing (Sanger)?
Next generation sequencing makes it much easier to create full genome data sets
Next generation sequencing increased DNA sequence output substantially
All of these
First generation sequencing requires prior knowledge of every DNA segment to be sequenced
First generation sequencing is capable of sequencing longer continuous strings of DNA (read length)
All of these
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 #52 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology
What is directional cloning?
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
Two restriction enzymes are used to cut both the plasmid and the subject DNA to be incorporated
All of these
None of these
Two restriction enzymes are used to cut both the plasmid and the subject DNA to be incorporated
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?
The phage is specially engineered to insert DNA when it is a recombinant phage
Subject DNA is annealed to sticky ends in the phage
A plate of bacteria is infected with the phage
None of these steps are necessary
All of these steps are necessary
All of these steps are necessary
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?
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 allows for only single-end reads, third next-generation sequencing allows for paired-end reads
Second next-generation sequencing uses emulsion PCR to amplify DNA, third next-generation sequencing uses bridge PCR to amplify DNA
Second next-generation sequencing requires amplification of DNA, but third next-generation sequencing can sequence single molecules
Second next-generation sequencing requires amplification of DNA, but third next-generation sequencing can sequence single molecules
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?
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
TAS amplifies conserved yet divergent genes, such as rRNA genes, to identify species. Many species do not have sequenced genomes.
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?
Polymerase cycling assembly
Polymerase chain reaction
Restriction endonuclease digestion
DNA ligation
Gibson assembly
Polymerase cycling assembly
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?
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.
The start codon should be 5' to the biochemical tag and the stop codon should be 3' to the protein of interest.
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?
Two blunt cutting restriction enzymes cannot be used for cloning
This method is a completely viable way to insert a gene into a plasmid backbone
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
Once DNA has been blunt cut by a restriction enzyme, it cannot re-ligate
There is no control over the orientation of the insertion into the plasmid backbone
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?
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
Calcium chloride surrounds the bacterial membrane and attracts negatively charged DNA
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 #57 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology
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?
The high concentration of calcium chloride in the transformation mixture needs to be diluted out to prevent lethality
None of the other answers
is too warm for bacterial growth
The transformed bacteria need time to transcribe and translate the antibiotic resistant gene on the plasmid
Bacteria only commence replication in liquid media and not agar media
The transformed bacteria need time to transcribe and translate the antibiotic resistant gene on the plasmid
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.