GRE Subject Test: Biology : Genetics, DNA, and Molecular Biology

Study concepts, example questions & explanations for GRE Subject Test: Biology

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Example Questions

Example Question #51 : Genetics, Dna, And Molecular Biology

Which of the following are commonly found in a eukaryotic RNA-polymerase-II-dependent promoter?

I. Shine-Delgarno sequence

II. TATA element

III. Ribosomal binding site

Possible Answers:

I only

I and III

II only

I, II, and III

Correct answer:

II only

Explanation:

Of the three choices, the only element commonly found in a eukaryotic promoter is a TATA element. This is the site where TBP (TATA binding protein) binds and begins to recruit other transcriptional machinery.

The Shine-Delgarno sequence is commonly found on prokaryotic mRNA and serves as a ribosomal binding site. Because promoters are regions of DNA, both option I and II do not really apply.

Example Question #52 : Genetics, Dna, And Molecular Biology

In eukaryotes, promoter sequences are regulatory elements found upstream of the transcription start site. Promoter sequences are required for transcription factors and RNA polymerase to recognize and bind to the DNA strand, thus promoting transcription of the genes on that strand and production of mRNA.

mRNA is ultimately translated into proteins, i.e. gene products. Consider a mutation in the promoter sequence that increases the affinity of RNA polymerase for the DNA strand. Compared to a sequence where the promoter sequence is wild-type, which of the outcomes below is most likely for this mutated promoter region?

Possible Answers:

Overexpression of the gene product

Loss of the gene product

The process described above has nothing to do with quantity of gene product

20% reduction in gene product

Altered tertiary structure of the gene product

Correct answer:

Overexpression of the gene product

Explanation:

The binding of RNA polymerase and transcription factors is tightly modulated by promoter elements. If affinity was increased compared to a wild-type sequence, we would expect that RNA polymerase would bind more easily to the sequence and produce more mRNA. Nothing about the nature of this mRNA is altered (since the coding sequences are unchanged); there is simply more of it, which would mean overexpression of the protein for which it codes.

Example Question #53 : Genetics, Dna, And Molecular Biology

What is the region of DNA where transcription factors and RNA polymerase bind, and that is also responsible for regulating transcription?

Possible Answers:

Intron 

Exon

Enhancer

Promoter

Insulator

Correct answer:

Promoter

Explanation:

The correct answer is promoter. The promoter is directly upstream of the start of transcription for a given gene. It is the site of transcription factor and RNA polymerase binding, and interacts with distant enhancers to regulate transcription. 

Example Question #54 : Genetics, Dna, And Molecular Biology

Eukaryotic transcription requires many proteins interacting in a coordinated fashion to drive the process of converting DNA to RNA. RNA polymerase, the enzyme that initiates transcription, needs a number of factors and components to being transcribing a gene. Which of the following answers is not one of these factors? 

Possible Answers:

Each of these are required for initiation of transcription

Activators

DNA polymerase

Core promoter sequence

Transcription factors

Correct answer:

DNA polymerase

Explanation:

DNA polymerase is a crucial factor required for replication of DNA, but is not a component utilized in the process of transcription. The core promoter sequence, activators, and transcription factors are all needed in order for RNA polymerase to begin the process. 

Example Question #55 : Genetics, Dna, And Molecular Biology

A protein that will be embedded in the plasma membrane is likely to be translated by __________

Possible Answers:

ribosomes bound to the Golgi apparatus

nuclear ribosomes

ribosomes bound to the endoplasmic reticulum

cytosolic ribosomes

Correct answer:

ribosomes bound to the endoplasmic reticulum

Explanation:

Most proteins that will be embedded in the plasma membrane are translated on ribosomes located in the rough endoplasmic reticulum. There are specific mechanisms and proteins that help insert the proteins into the membrane while they are being translated. Free-floating proteins are more likely to be translated in the cytosol. The nucleus and the Golgi do not have ribosomes used for translation, though the Golgi can play an important role in transporting proteins from the rough endoplasmic reticulum to the membrane.

Example Question #171 : Gre Subject Test: Biology

What site in the ribosome contains the elongating polypeptide?

Possible Answers:

E site

P site

A site

R site

Correct answer:

P site

Explanation:

A tRNA that is attached to one amino acid will enter the ribosomal complex at the A site. It will then receive the growing polypeptide chain from the previous tRNA and move into the P site. Once handing off the chain, the tRNA that no longer has an amino acid will exit the ribosome at the E site.

The peptide chain is always anchored in the P site, where peptide bond synthesis occurs.

Example Question #172 : Gre Subject Test: Biology

Which of the following is true concerning the genetic code?

Possible Answers:

Translation typically ends once the whole mRNA is read by the ribosome

One codon can code for multiple amino acids

A codon codes for one amino acid

An amino acid has only one codon

Correct answer:

A codon codes for one amino acid

Explanation:

The genetic code is unambiguous, meaning that each given codon will always code for the same amino acid. An amino acid, however, can be coded for by multiple codons, making the genetic code degenerative in nature. Once a stop codon is reached during translation, the ribosome stops making the protein.

Example Question #51 : Genetics, Dna, And Molecular Biology

Which of the following post-transcriptional modifications occur in the nucleus?

I. 5' capping

II. Splicing

III. Polyadenylation

Possible Answers:

I, II, and III

I and III

II and III

I and II

Correct answer:

I, II, and III

Explanation:

All of the post-transcriptional modifications listed occur in the nucleus. Each is important in the process of turning pre-mRNA into mature mRNA that can successfully exit the nucleus and enter into translation. These modifications allow for the appropriate recognition by ribosomes and serve to enhance the stability of the mRNA molecule.

The 5' guanosine cap is added to one end of the RNA strand, and a poly-A tail is added to the other. These modifications serve to help with ribosome recognition and prevent degradation. Spicing involves the removal of non-coding introns from the RNA transcript, allowing for translation of the proper sequence.

Example Question #174 : Gre Subject Test: Biology

Which of the following post-translation modifications cannot be classified as lipidation?

Possible Answers:

Addition of GPI-anchor

Myristoylation

Palmityolation

Prenylation

Ubiquitination 

Correct answer:

Ubiquitination 

Explanation:

Ubiquitination is the only option in which the modification to the protein does not include the binding of a lipid group to a protein. Rather, it is the addition of another peptide to the existing protein.

Example Question #1 : Understanding M Rna And Protein Modifications

The process of polyadenylation results in the addition of a poly-A tail to mRNA after transcription. The poly-A tail consists of approximately 150-200 adenine bases at the 3' end of the mRNA. Which of the following best describes the purpose of polyadenylation in mRNA processing?

Possible Answers:

Protection against degradation in the cytoplasm

Initiation of transcription

Enhancement of intron splicing

Transport of mRNA into the nucleus

Coupling mRNA to the spliceosome

Correct answer:

Protection against degradation in the cytoplasm

Explanation:

Polyadenylation results in a long chain of adenosine monophosphate residues being added to the 3' end of a pre-mRNA as transcription is terminating. The poly-A tail provides stability to the mRNA molecule as it is transported through the cell to its ultimate location. Without this modification, the shorter mRNA would be degraded by enzymes within the cytoplasm. The other functions listed as answers are in no part dependent on the poly-A tail. 

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