Question 1

What must be included, in addition to the coding exons of the gene, in order for the expression of a eukaryotic gene engineered into a bacterial colony?
A)the introns
B)eukaryotic polymerases
C)a bacterial promoter sequence
D)eukaryotic ribosomal subunits
E)eukaryotic tRNAs

Accepted Answer

In order for a eukaryotic gene to be expressed in a bacterial colony, a bacterial promoter sequence must be included. Bacteria and eukaryotes have different types of RNA polymerases, ribosomal subunits, and tRNAs, so including these components would not necessarily facilitate expression in a bacterial colony. The introns, while important for eukaryotic gene expression, are spliced out before the mRNA is exported from the nucleus, so they would not be present in the mRNA that would be used in the bacterial colony.

Question 2

In comparing DNA replication with RNA transcription in the same cell, which of the following is true only of replication?
A)It uses RNA polymerase.
B)It makes a new molecule from its 5' end to its 3' end.
C)The process is extremely fast once it is initiated.
D)The process occurs in the nucleus of a eukaryotic cell.
E)The entire template molecule is represented in the product.

Accepted Answer

DNA replication involves copying the entire template molecule, resulting in a complete representation of the original DNA sequence in the newly synthesized DNA. In contrast, RNA transcription only transcribes specific regions of DNA into RNA, not the entire DNA molecule.

Question 3

Why might a point mutation in DNA make a difference in the level of protein's activity?
A)It might result in a chromosomal translocation.
B)It might exchange one stop codon for another stop codon.
C)It might exchange one serine codon for a different serine codon.
D)It might substitute an amino acid in the active site.
E)It might substitute the N-terminus of the polypeptide for the C-terminus.

Accepted Answer

Substituting an amino acid in the active site can affect the protein's ability to bind to its substrate or catalyze a reaction, therefore altering its activity level. Chromosomal translocations and changes in the N-terminus or C-terminus would likely have much larger effects on the protein's structure and function, while switching between codons for the same amino acid would not change the protein sequence. Swapping stop codons could affect the length of the protein but not its activity level.

Question 4

In the 1920s, Muller discovered that X-rays caused mutation in Drosophila. In a related series of experiments in the 1940s, Charlotte Auerbach discovered that chemicals-she used nitrogen mustards-have a similar effect. A new chemical food additive is developed by a cereal manufacturer. Why do we test for its ability to induce mutation?
A)We worry that it might cause mutation in cereal grain plants.
B)We want to make sure that it does not emit radiation.
C)We want to be sure that it increases the rate of mutation sufficiently.
D)We want to prevent any increase in mutation frequency.
E)We worry about its ability to cause infection.

Accepted Answer

Testing for the ability to induce mutation is important to prevent any increase in mutation frequency that could lead to harmful effects. Mutations can lead to genetic disorders, cancer, and other health problems, so it is important to ensure that new chemicals, such as food additives, do not have mutagenic properties.

Question 5

Which of the following DNA mutations is the most likely to be damaging to the protein it specifies?
A)a base-pair deletion
B)a codon substitution
C)a substitution in the last base of a codon
D)a codon deletion
E)a point mutation

Accepted Answer

A base-pair deletion mutation results in a shift of the reading frame, leading to a frameshift mutation. This alters the entire sequence of codons downstream of the deletion, often resulting in premature stop codons and a dysfunctional protein. Other mutations listed may still be damaging, but a base-pair deletion is most likely to have a fundamentally negative impact on the protein's function.

Question 6

What is the effect of a nonsense mutation in a gene?
A)It changes an amino acid in the encoded protein.
B)It has no effect on the amino acid sequence of the encoded protein.
C)It introduces a premature stop codon into the mRNA.
D)It alters the reading frame of the mRNA.
E)It prevents introns from being excised.

Accepted Answer

A nonsense mutation creates a premature stop codon in the mRNA sequence, leading to an incomplete or truncated protein. This can have detrimental effects on the protein's function, as it may lack essential functional domains or be rapidly degraded.

Question 7

The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in
A)a base-pair substitution.
B)a nucleotide mismatch.
C)a frameshift mutation.
D)a polypeptide missing an amino acid.
E)a nonsense mutation.

Accepted Answer

The deletion of a single codon in the genetic code of people with cystic fibrosis results in the absence of a specific amino acid in the polypeptide chain, rather than a frameshift or a substitution. This is because a codon, which is a sequence of three nucleotides, codes for a single amino acid. Removing one codon thus removes one amino acid from the polypeptide, not altering the reading frame or substituting nucleotides.

Question 8

Which of the following is true of transcription in domain Archaea?
A)It is regulated in the same way as in domain Bacteria.
B)There is only one kind of RNA polymerase.
C)It is roughly simultaneous with translation.
D)Promoters are identical to those in domain Eukarya.
E)It terminates in a manner similar to bacteria.

Accepted Answer

The answer of Which of the following is true of...

Question 9

Changes in a single nucleotide pair within a gene is called
A)substitution.
B)translocation.
C)point mutation.
D)silent mutation.
E)evolution.

Accepted Answer

A change in a single nucleotide pair within a gene is called a point mutation. This can include substitutions, insertions, or deletions of nucleotides. Translocations involve the movement of a segment of DNA from one chromosome to another, and silent mutations result in no change to the protein sequence due to the redundancy of the genetic code. Evolution is a process that involves changes in allele frequencies in a population over time, and is not specific to a single nucleotide pair within a gene.

Question 10

Of the following, which is the most current description of a gene?
A)a unit of heredity that causes formation of a phenotypic characteristic
B)a DNA subunit that codes for a single complete protein
C)a DNA sequence that is expressed to form a functional product: either RNA or polypeptide
D)a DNA-RNA sequence combination that results in an enzymatic product
E)a discrete unit of hereditary information that consists of a sequence of amino acids

Accepted Answer

This is currently the most accurate definition of a gene as it accounts for the fact that genes can code for both RNA and polypeptides, and that not all DNA sequences are expressed. Option A is outdated as not all genes directly cause the formation of a phenotypic characteristic. Option B is limited as some genes can code for multiple proteins through alternative splicing, and some proteins are made up of multiple subunits coded for by different genes. Option D is incorrect as enzymes can also be coded for by multiple genes, and not all DNA-RNA sequences result in enzymatic products. Option E is incorrect as amino acid sequences are not always the ultimate product of gene expression, and not all genes code for proteins.

Question 11

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?
A)a deletion of a codon
B)a deletion of two nucleotides
C)a substitution of the third nucleotide in an ACC codon
D)a substitution of the first nucleotide of a GGG codon
E)an insertion of a codon

Accepted Answer

A deletion of two nucleotides causes a frameshift mutation, altering the reading frame of the mRNA and potentially affecting every subsequent amino acid in the polypeptide, likely resulting in a nonfunctional protein.

Question 12

Which of the following statements is true about protein synthesis in prokaryotes?
A)Extensive RNA processing is required before prokaryotic transcripts can be translated.
B)Translation can begin while transcription is still in progress.
C)Prokaryotic cells have complicated mechanisms for targeting proteins to the appropriate cellular organelles.
D)Translation requires antibiotic activity.
E)Unlike eukaryotes, prokaryotes require no initiation or elongation factors.

Accepted Answer

In prokaryotes, both transcription and translation occur in the cytoplasm, and since prokaryotic mRNAs are not modified extensively, translation can begin while transcription is still in progress. This process is called coupled transcription-translation. Prokaryotic cells do not have complicated mechanisms for targeting proteins to specific cellular organelles like in eukaryotes, and antibiotics may interfere with translation, but they are not required for it to occur. Prokaryotes have initiation and elongation factors just like eukaryotes.

Question 13

If a nucleotide substitution switched a U for a C, such that the codon was read as CGC instead of CGU, what would the effect be?
A)a misfolding of the protein
B)an incomplete protein
C)nothing, as the third nucleotide does not determine the amino acid used.
D)nothing, since both these codons code for arginine
E)it would initiate a tumour

Accepted Answer

Both CGU and CGC code for the amino acid arginine, so this nucleotide substitution would not result in a change in the amino acid sequence of the protein.

Question 14

Which small-scale mutation would be most likely to have a catastrophic effect on the functioning of a protein?
A)a base substitution
B)a base deletion near the start of a gene
C)a base deletion near the end of the coding sequence, but not in the terminator codon
D)deletion of three bases near the start of the coding sequence, but not in the initiator codon
E)a base insertion near the end of the coding sequence, but not in the terminator codon

Accepted Answer

A base deletion near the start of a gene has the potential to cause a frameshift mutation, shifting the reading frame of the codons downstream of the deletion. This can result in a completely different amino acid sequence being produced, and therefore a dysfunctional protein.

Question 15

Suppose that a mutation alters the formation of a tRNA such that it still attaches to the same amino acid (phe)but its anticodon loop has the sequence AAU that binds to the mRNA codon UUA (that usually specifies leucine leu).
A)The modified tRNA will cause this mRNA to make only nonfunctioning product.
B)The tRNA-leu will not be able to enter the site of the ribosome to bind to the UUA.
C)One mutated tRNA molecule will be relatively inconsequential because it will compete with many "normal" ones.
D)The tRNA will be so unstable that it will not participate in translation.
E)The mutated tRNA will result in an amino acid variant in all copies of the protein.

Accepted Answer

The presence of one mutated tRNA molecule among many normal ones means it will have a relatively minor effect due to competition with the normal tRNAs that correctly interpret the mRNA codon.

Question 16

A frameshift mutation could result from
A)a base insertion only.
B)a base deletion only.
C)a base substitution only.
D)deletion of three consecutive bases.
E)either an insertion or a deletion of a base.

Accepted Answer

A frameshift mutation occurs when one or more bases are added or deleted from DNA, which causes the reading frame to shift. This can result in a completely different amino acid sequence in the protein that is coded for. Both base insertions and base deletions can cause a frameshift mutation. Therefore, the best choice is either an insertion or a deletion of a base.

Question 17

If a protein is coded for by a single gene and this protein has six clearly defined domains, which number of exons below is the gene likely to have?
A)1
B)5
C)8
D)12
E)14

Accepted Answer

Each domain in the protein is likely to be encoded by a separate exon. Therefore, the gene would require at least six exons to encode the six domains. However, additional exons may be present for regulatory regions or alternative splicing. Option C provides the closest number of exons to meet the minimum requirement.

Question 18

Gene expression in the domain Archaea in part resembles that of bacteria and in part that of the domain Eukarya. In which way is it most like the domain Eukarya?
A)Domain Archaea have numerous transcription factors.
B)Initiation of translation is like that of domain Eukarya.
C)There is only one RNA polymerase.
D)Transcription termination often involves attenuation.
E)Post-transcriptional splicing is like that of Eukarya.

Accepted Answer

Archaea have numerous transcription factors similar to Eukarya, which is a key feature distinguishing their gene expression from bacteria, which typically have fewer transcription factors.

Question 19

Which of the following mutations is most likely to cause a phenotypic change?
A)a duplication of all or most introns
B)a large inversion whose ends are each in intergenic regions
C)a nucleotide substitution in an exon coding for a transmembrane domain
D)a single nucleotide deletion in an exon coding for an active site
E)a frameshift mutation one codon away from the 3' end of the nontemplate strand

Accepted Answer

A single nucleotide deletion in an exon coding for an active site is most likely to cause a phenotypic change because it can directly affect the protein's function by altering its active site, potentially leading to a loss or change in function.

Question 20

The molecule that links the genotype and phenotype of an organism, is (are)
A)protein.
B)mRNA.
C)tRNA.
D)receptor complexes.
E)ploidy.

Accepted Answer

The answer of The molecule that links the genotype and...

Quiz 17: From Gene to Protein

What must be included, in addition to the coding exons of the gene, in order for the expression of a eukaryotic gene engineered into a bacterial colony?

In comparing DNA replication with RNA transcription in the same cell, which of the following is true only of replication?

Why might a point mutation in DNA make a difference in the level of protein's activity?

Which of the following DNA mutations is the most likely to be damaging to the protein it specifies?

What is the effect of a nonsense mutation in a gene?

The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in

Which of the following is true of transcription in domain Archaea?

Changes in a single nucleotide pair within a gene is called

Of the following, which is the most current description of a gene?

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?

Which of the following statements is true about protein synthesis in prokaryotes?

If a nucleotide substitution switched a U for a C, such that the codon was read as CGC instead of CGU, what would the effect be?

Which small-scale mutation would be most likely to have a catastrophic effect on the functioning of a protein?

Suppose that a mutation alters the formation of a tRNA such that it still attaches to the same amino acid (phe) but its anticodon loop has the sequence AAU that binds to the mRNA codon UUA (that usually specifies leucine leu) .

A frameshift mutation could result from

If a protein is coded for by a single gene and this protein has six clearly defined domains, which number of exons below is the gene likely to have?

Gene expression in the domain Archaea in part resembles that of bacteria and in part that of the domain Eukarya. In which way is it most like the domain Eukarya?

Which of the following mutations is most likely to cause a phenotypic change?

The molecule that links the genotype and phenotype of an organism, is (are)