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AP®BiologyCollege BoardExam QuestionsUnit 6: Gene Expression & RegulationMutations

Mutations (College Board AP® Biology): Exam Questions

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1
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A population of bacteria is exposed to an antibiotic. After several generations, some bacteria survive and reproduce, while others do not. Genetic analysis shows that a mutation in one of the bacterial genes is present only in the surviving individuals.

Which of the following best describes the possible effect of this mutation?

  • The mutation provided an advantage, allowing the bacteria to survive the antibiotic exposure.

  • The mutation had no effect on survival, as all mutations are neutral in their impact.

  • The mutation was harmful, preventing the bacteria from reproducing in the presence of the antibiotic.

  • The mutation reduced the ability of the bacteria to metabolize nutrients, making survival less likely.

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In a population of flowering plants, some individuals have an extra set of chromosomes compared to the typical diploid plants. These polyploid plants grow larger and produce more flowers than their diploid counterparts.

Which of the following best explains how changes in chromosome number can impact an organism’s phenotype?

  • Polyploidy can result in increased size and vigor in plants due to additional copies of genes.

  • Chromosomal changes always lead to sterility and developmental disorders.

  • Extra chromosomes are always harmful and reduce an organism’s ability to survive and reproduce.

  • Changes in chromosome number only occur in plants.

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3
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A doctor conducts a genetic analysis on a female patient with short stature, delayed puberty, and infertility. The karyotype reveals that the patient has only one X chromosome instead of the typical two.

Which of the following diseases results from a chromosomal mutation leading to the loss of an X chromosome?

  • Sickle cell anemia

  • Turner syndrome

  • Huntington's disease

  • X-linked color blindness

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Which of the following best describes the term horizontal transmission?

  • The transfer of genetic material from parent to offspring during reproduction.

  • The exchange of genetic material between individuals of the same generation.

  • The inheritance of mutations that occur in gametes and are passed to offspring.

  • The transfer of genes exclusively through mitosis in eukaryotic cells.

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The image shows a mutation in which a single DNA base has changed, leading to a different amino acid in the protein sequence.

Which of the following best describes a possible effect of this type of mutation?

Diagram showing DNA sequence mutation, where one 'C' base is replaced, changing the amino acid from histidine (His) to proline (Pro).

  • The codon encoding an amino acid was changed to a stop codon, shortening the polypeptide.

  • Mutations always result in the production of a non-functional protein.

  • It is a silent mutation so there will be no change in the polypeptide chain.

  • The sequence of amino acids may code for a different protein structure.

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During the replication of DNA spontaneous errors may occur, causing mutations. Which of the following mutations is most likely to be classified as a frameshift mutation?

  • Substitution of one base.

  • Insertion of a nucleotide.

  • Change in chromosome number.

  • Inversion of a gene section.

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A polypeptide has the amino acid sequence: 

histidine – glutamine – lysine – alanine – valine – histidine – valine

The table below gives the tRNA anticodons for each amino acid.

amino acid

tRNA anticodons

histidine

valine 

lysine 

alanine 

glutamine

CAU

GUA

AAA

GCU

CAG

A mutation causes the 18th base in the DNA sequence to be deleted.

Which of the following shows the amino acid sequence after this mutation has occurred?

  • histidine – glutamine – lysine – alanine – valine – histidine

  • histidine – glutamine – lysine – alanine – valine – glutamine-valine

  • histidine – glutamine – lysine – alanine – valine – glutamine

  • histidine – glutamine – lysine – alanine – valine – histidine – valine

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A bacterial population exposed to ionizing radiation may experience a higher rate of mutations.

Which of the following mechanisms is most likely to cause this increase in mutation rates?

  • Decreased gene expression.

  • Alteration in cell membrane structure.

  • Increased protein synthesis.

  • Damage to DNA strands.

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A duplication mutation is a type of genetic mutation where a section of DNA containing a gene is copied. The evolution of the hemoglobin gene family is an example of gene duplication leading to the introduction of new alleles and new biological function.

Which of the following is the most likely prediction of the effects of a duplication mutation in a gene encoding a critical protein, such as hemoglobin?

  • It is always harmful and leads to the loss of protein function.

  • It will result in the production of larger proteins than the original protein.

  • It can create an opportunity for evolutionary change by allowing one gene copy to evolve a new function.

  • It introduces a premature stop codon, resulting in incomplete protein synthesis.

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A population of bacteria is exposed to an antibiotic over several generations. Scientists observe that the bacteria evolve resistance to the antibiotic through a mutation in the gene encoding a membrane transport protein.

Which of the following best explains why this mutation increased in frequency in the bacterial population?

  • The antibiotic increased the mutation rate in the bacterial population, directly causing the resistance mutation to appear.

  • Bacteria with the mutation survived and reproduced more successfully than those without it.

  • The mutation was inherited from the parent bacteria and occurred in all individuals simultaneously.

  • Mutations occur in response to environmental stress, ensuring that all bacteria become resistant over time.

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Cystic fibrosis is a disease caused by a mutation. The pedigree diagram in Figure 1 provides information about the inheritance of the cystic fibrosis mutation over three generations within one family.

Pedigree chart showing genetic transmission of cystic fibrosis in a family. Two females (4, 8) with cystic fibrosis, represented by filled circles.
Figure 1. Genetic pedigree diagram showing inheritance of cystic fibrosis.

Which of the following conclusions is supported by Figure 1?

  • Cystic fibrosis is caused by a dominant allele that affects males and females equally.

  • Cystic fibrosis is a recessive mutation that is located on the X chromosome.

  • Cystic fibrosis is a recessive mutation which is not located on a sex chromosome.

  • Cystic fibrosis is caused by a dominant allele that affects females only.

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A mutation occurs in a gene that encodes a transcription factor responsible for activating the expression of hexokinase, an enzyme that catalyzes the first step of glycolysis. Hexokinase phosphorylates glucose, converting it into glucose-6-phosphate, which prevents glucose from leaving the cell and allows glycolysis to proceed. The mutation reduces the ability of the transcription factor to bind to the promoter region of the hexokinase gene, leading to significantly lower enzyme production.

Which of the following best describes the likely impact of this mutation on cellular function?

  • The mutation decreases ATP production by limiting the rate of glycolysis, reducing the energy available for cellular processes.

  • The mutation increases carbon dioxide production, as less pyruvate enters the krebs cycle.

  • The mutation leads to a change in the structure of the active site of hexokinase, making it unable to bind to glucose.

  • The mutation causes a buildup of glucose in the cytoplasm, which acts as a non-competitive inhibitor of oxidative phosphorylation in the mitochondria.

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Edwards syndrome is a rare but serious condition that influences birth weight and development during infancy. Death rates during infancy are high. Figure 1 below shows the karyogram of an individual with Edwards syndrome.

Diagram of human chromosomes 1 to 22 and sex chromosomes X and Y, displayed in pairs, showcasing their distinct shapes and sizes. Chromosome position number 18 has 3 chromosomes present rather than 2.
Figure 1. Karyogram of a individual with Edwards syndrome

With reference to Figure 1, which of the following describes the events that have led to the development of Edwards syndrome?

  • A mutation in mitosis early in embryonic development caused a third copy of chromosome 18 to appear in some but not all cells, resulting in the development of Edwards syndrome.

  • A missing Y chromosome during fertilization caused the developmental abnormalities associated with Edwards syndrome by disrupting normal gene expression.

  • An error during meiosis resulted in an extra copy of chromosome 18, leading to trisomy 18 and the developmental abnormalities seen in Edwards syndrome.

  • Fertilization by two sperm (dispermy) instead of one introduced an extra set of chromosomes, leading to abnormalities in chromosome number, including an extra chromosome 18.

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Hereditary transthyretin amyloidosis (hATTR) is a genetic disorder caused by a mutation in the gene coding for transthyretin, a blood protein. This mutation leads to misfolded transthyretin proteins that form harmful clumps in tissues such as the cardiovascular and nervous systems. Some treatments for hATTR involve drugs that bind to mutant mRNA molecules.

Which of the following best explains how these drugs could be effective in treating hATTR amyloidosis?

  • They degrade or block the mutated mRNA, preventing the translation and the production of the misfolded protein.

  • Targeting mutant mRNA allows for correction of the genetic mutation, restoring normal transthyretin function and preventing misfolding of transthyretin proteins.

  • They increase the rate of translation, producing more functional transthyretin protein to counteract the clumps.

  • The binding of drugs to mutant mRNA increases the efficiency of alternative splicing, promoting the production of a functional transthyretin isoform.

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Cystic fibrosis (CF) is a genetic disorder caused by mutations in the CFTR gene, which encodes a chloride ion channel involved in regulating ion and water balance in epithelial cells. Researchers hypothesize that expression of the CFTR gene is regulated by a transcription factor that binds to its promoter region.

Which of the following questions will best help guide researchers toward a direct test of their hypothesis?

  • Are mutations in other ion channel genes also associated with cystic fibrosis symptoms?

  • In what types of cells is the CFTR gene actively transcribed?

  • Are mutations in the CFTR gene found in other organisms with cystic fibrosis?

  • Does reducing transcription factor activity decrease CFTR mRNA levels in cells?

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