GRE Subject Test: Biology › Genetic Sequences, Transcription, and Translation
An error occurs during DNA replication, resulting in the insertion of a base pair. Replication of the original 3' DNA strand (template) produces a mutant 3' strand (mutant), as diagrammed below:
Template
3' - AUGGCCATTTTTATA - 5'
Mutant
3'- AUGCGCCATTTTTATA - 5'
Of the answers below, which best describes the type of mutation depicted above?
Frameshift mutation
Missense mutation
Nonsense mutation
Duplication mutation
Repeat expansion
The addition of a number of nucleotides that is not a multiple of three shifts the reading frame of the codons in the gene. One base pair was inserted early in the strand, thus shifting the codon reading frame +1 to the right.
Missense and nonsense mutations imply base pair substitutions, which did not occur in the diagram. Similarly, nothing was duplicated, and repeat expansion would require multiple repetitions of a short DNA sequence.
An error occurs during DNA replication, resulting in the insertion of a base pair. Replication of the original 3' DNA strand (template) produces a mutant 3' strand (mutant), as diagrammed below:
Template
3' - AUGGCCATTTTTATA - 5'
Mutant
3'- AUGCGCCATTTTTATA - 5'
Of the answers below, which best describes the type of mutation depicted above?
Frameshift mutation
Missense mutation
Nonsense mutation
Duplication mutation
Repeat expansion
The addition of a number of nucleotides that is not a multiple of three shifts the reading frame of the codons in the gene. One base pair was inserted early in the strand, thus shifting the codon reading frame +1 to the right.
Missense and nonsense mutations imply base pair substitutions, which did not occur in the diagram. Similarly, nothing was duplicated, and repeat expansion would require multiple repetitions of a short DNA sequence.
In a eukaryotic cell, a molecule of pre-mRNA is found to have four exons and three introns. Which of the following are possible combinations of the exons, if the order in which they are written is the order in which they will be translated?
I. Exon 1, Exon 2, Exon 3, Exon 4
II. Exon 1, Exon 3, Exon 4
III. Exon 4, Exon 1, Exon 2, Exon 3
I and II
I only
I, II, and III
II only
This question is asking about alternative splicing. Alternative splicing is a means by which several different proteins can arise from the same pre-mRNA due to the order in which the exons are organized. This typically takes the form of exon skipping. Therefore, both 1 and 2 are potential mature mRNAs that could arise from this pre-mRNA. Option 3 is not an acceptable transcript, however, because alternative splicing maintains the integrity of the genomic order of the exons (i.e. exon 4 will not come before exon 1, 2, or 3).
In a eukaryotic cell, a molecule of pre-mRNA is found to have four exons and three introns. Which of the following are possible combinations of the exons, if the order in which they are written is the order in which they will be translated?
I. Exon 1, Exon 2, Exon 3, Exon 4
II. Exon 1, Exon 3, Exon 4
III. Exon 4, Exon 1, Exon 2, Exon 3
I and II
I only
I, II, and III
II only
This question is asking about alternative splicing. Alternative splicing is a means by which several different proteins can arise from the same pre-mRNA due to the order in which the exons are organized. This typically takes the form of exon skipping. Therefore, both 1 and 2 are potential mature mRNAs that could arise from this pre-mRNA. Option 3 is not an acceptable transcript, however, because alternative splicing maintains the integrity of the genomic order of the exons (i.e. exon 4 will not come before exon 1, 2, or 3).
Which of the following post-translation modifications cannot be classified as lipidation?
Ubiquitination
Myristoylation
Palmityolation
Prenylation
Addition of GPI-anchor
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.
Which of the following post-translation modifications cannot be classified as lipidation?
Ubiquitination
Myristoylation
Palmityolation
Prenylation
Addition of GPI-anchor
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.
Which of the following accurately describes the promoter?
A sequence of DNA used to signal the beginning point of transcription
The attachment point for a ribosome before translation
The binding site for DNA polymerase on DNA
The protein that attaches to DNA in order to create mRNA
The promoter is a specific segment of DNA that signals the starting point of transcription. RNA polymerase attaches to the promoter and proceeds to create the mRNA primary transcript.
DNA polymerase binds to the RNA primer to begin DNA replication. Ribosomes bind to the 5' cap on eukaryotic mRNA.
Which of the following accurately describes the promoter?
A sequence of DNA used to signal the beginning point of transcription
The attachment point for a ribosome before translation
The binding site for DNA polymerase on DNA
The protein that attaches to DNA in order to create mRNA
The promoter is a specific segment of DNA that signals the starting point of transcription. RNA polymerase attaches to the promoter and proceeds to create the mRNA primary transcript.
DNA polymerase binds to the RNA primer to begin DNA replication. Ribosomes bind to the 5' cap on eukaryotic mRNA.
Which conditions would result in the largest levels of lac operon transcription?
High lactose and low glucose
High lactose and high glucose
Low lactose and high glucose
Low lactose and low glucose
The important thing to remember about the lac operon is that it is transcribed when glucose is absent from the cell, but lactose is present and can be utilized. As a result, the operon's transcription would be high if there are both high levels of lactose available, and very little amounts of glucose.
Which conditions would result in the largest levels of lac operon transcription?
High lactose and low glucose
High lactose and high glucose
Low lactose and high glucose
Low lactose and low glucose
The important thing to remember about the lac operon is that it is transcribed when glucose is absent from the cell, but lactose is present and can be utilized. As a result, the operon's transcription would be high if there are both high levels of lactose available, and very little amounts of glucose.