GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Knockout and Mutation Analyses

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

varsity tutors app store varsity tutors android store

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 #1 : Help With Knockout And Mutation Analyses

A scientist is trying to create a mutant cell line that has a specific non-functional protein. After many different mutagenesis techniques, he is unable to create a cell line with the mutation he desires. Which of the follow might be the reason he cannot generate a mutant for this protein?

Possible Answers:

The gene is buried deep within a region of euchromatin

The mutant phenotype is lethal

The gene is highly conserved throughout evolution

The gene is buried deep within a region of heterochromatin

Correct answer:

The mutant phenotype is lethal

Explanation:

If he cannot generate a mutant, it is most likely because the mutant phenotype is lethal. In theory, this researcher was successful in mutating the target gene, however the result of the mutation was a failure during development. This would prevent any potential offspring with the mutation from developing, resulting in no viable specimens for the study.

Many proteins are conserved throughout evolution, but can still be easily mutated. For example, the gene for the protein hemoglobin is well-preserved between animal species, but can still be manipulated to generate animal models for various disorders. The distinction between heterochromatin and euchromatin doesn't really explain why the researcher would be unable to generate a mutant. 

Example Question #2 : Help With Knockout And Mutation Analyses

Which of the following techniques can be used for mutagenesis?

Possible Answers:

Homologous recombination

All of these answers

UV light exposure

PCR

Correct answer:

All of these answers

Explanation:

All of the given answers could potentially be used in a mutagenesis procedure.

For PCR, special primers can be designed to introduce site-directed mutagenesis. UV light is a common mutagen and could be used to make random mutations throughout the genome. Homologous recombination can be used to incorporate a non-functional copy of a gene into an organism.

Example Question #3 : Help With Knockout And Mutation Analyses

In a knockout, what is a chimeric mouse?

Possible Answers:

A mouse derived only from the modified stem cells

A mouse homozygous for the knockout

A mouse heterozygous for the knockout

A mouse derived from two different types of stem cells

Correct answer:

A mouse derived from two different types of stem cells

Explanation:

A chimeric mouse results from implanting altered stem cells into a fertile mother. Her offspring will consist of mice made partially of her own stem cells and partially from the stem cells that were implanted by the researcher. The term chimera does not necessarily reflect upon the genotype of the mice.

Example Question #4 : Help With Knockout And Mutation Analyses

Which of the following gene editing technologies is not utilized to programmably alter/mutate specific genomic loci in uni/multicellular organisms? 

Possible Answers:

Restriction endonucleases 

Zinc-finger nucleases (ZFNs)

Transcription activator-like effector nucleases (TALENs)

Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9

None of these

Correct answer:

Restriction endonucleases 

Explanation:

CRISPR/Cas9 utilizes a gRNA sequence that directs the endonuclease activity of Cas9 to specific PAM recognition sites within the genome. TALENs harbor a DNA binding domain and a nuclease domain. Binding of the TALEN to a specific loci activates the nuclease domain to cut at that specific locus. ZFNs, similar to TALENs, have a Zinc-finger domain that binds specific DNA sequences and a DNA-cleavage domain. The above technologies are programmable to target varying genomic loci. Restriction endonucleases alone, however, are not utilized to stably alter genomes. 

Example Question #5 : Help With Knockout And Mutation Analyses

A student researcher is trying to identify genes that are turned on by a specific transcription factor. Which of the following techniques can the student use? 

Possible Answers:

Transcription factor morpholino knockdown with RNA sequencing 

Transcription factor morpholino knockdown with microarray analysis

All of these

Chromatin immunoprecipitation with sequencing 

Chromatin immunoprecipitation with microarray analysis

Correct answer:

All of these

Explanation:

The correct answer is all of the answers. Chromatin immunoprecipitation with sequencing uses an antibody specific to the transcription factor to pull down crosslinked transcription factor-DNA complexes. Sequencing of this DNA then determines the promoters of genes that this transcription factor binds. Chromatin immunoprecipitation with microarray analysis is similar, however, the DNA bound in complex is analyzed by a designed microarray of select genes (promoters). Morpholinos are anti-sense DNA oligomers that prevent translation of their target genes, and as such, are an efficient way to knockdown gene expression. By knocking down a transcription factor, we can measure differentially regulated genes compared to a control. The read-out experiment for measuring up or down-regulated genes in the knockout condition can be either by RNA-sequencing or by microarray analysis.  

Example Question #5 : Help With Knockout And Mutation Analyses

Which of the following is not a way to disrupt the expression of a specific gene?

Possible Answers:

Short hairpin RNAs

Small interfering RNAs

Morpholino

CRISPR/Cas9

None of these

Correct answer:

None of these

Explanation:

Morpholinos, short hairpin RNAs, and small interfering RNAs are methodologies to transiently knockdown the expression of a specific gene by complementary base pairing with the transcribed mRNA of gene of interest, inhibiting translation. CRISPR/Cas9 permanently mutates a gene of interest by introducing a double-stranded DNA break within the gene. All of these technologies are widely used in disruption of gene expression.

Example Question #6 : Help With Knockout And Mutation Analyses

When using the CRISPR/Cas9 gene editing technology, what genomic functional element does the Cas9 endonuclease recognize to indicate where it introduces a double stranded break? 

Possible Answers:

TATA box

Guide RNA 

Trans-activating CRISPR-RNA 

Protospacer adjacent motifs 

None of the other answers 

Correct answer:

Protospacer adjacent motifs 

Explanation:

The correct answer is protospacer adjacent motifs (PAMs). gRNAs guide Cas9 to a specific genomic loci, however, in order for Cas9 to introduce a DNA break, a PAM, which are 5' NGG 3' sequences, must be present at the loci as well. TATA boxes are functional elements in eukaryotic promoters that promote activation of transcription. Trans-activating CRISPR-RNAs are important for pathogen defense in bacteria and archaea, but are not utilized in the gene editing technology. 

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

1 Diagnostic Test 201 Practice Tests Question of the Day Flashcards Learn by Concept
Learning Tools by Varsity Tutors

Incompatible Browser

Please upgrade or download one of the following browsers to use Instant Tutoring: