Question 1

A researcher is attempting to generate induced pluripotent stem cells (iPSCs) from adult fibroblasts. Which of the following factors is primarily responsible for the increased oncogenic risk associated with iPSC generation?

Accepted Answer

The inclusion of c-Myc in the reprogramming cocktail, which can drive tumorigenesis.

Question 2

A patient presents with hyperextensible skin, atrophic scarring, and joint hypermobility. Genetic testing reveals a mutation in the COL5A1 gene. Which extracellular matrix component is most directly affected, and what is its primary structural role?

Accepted Answer

Type V collagen; regulates fibrillar collagen assembly and tensile strength.

Question 3

A cell is exposed to a drug that disrupts lipid rafts. Which of the following cellular processes is most likely to be impaired as a result?

Accepted Answer

Signal transduction pathways that require concentrated membrane receptors.

Question 4

A mutation in the gene encoding the β2 integrin subunit would most directly impair which step of leukocyte extravasation during inflammation?

Accepted Answer

Firm adhesion of leukocytes to the endothelium.

Question 5

A scientist is studying actin treadmilling in vitro. Which of the following best describes the process and the role of ATP in actin filament dynamics?

Accepted Answer

Actin monomers add preferentially to the plus end with ATP bound, and ATP hydrolysis after incorporation destabilizes the minus end, leading to treadmilling.

Question 6

A patient with chronic respiratory infections, situs inversus, and infertility is found to have a defect in axonemal dynein. Which cellular structure is most directly affected, and what is its microtubule arrangement?

Accepted Answer

Motile cilia; 9+2 microtubule arrangement.

Question 7

A cell is treated with Taxol (paclitaxel). Which of the following best describes the drug's mechanism of action and its effect on dividing and non-dividing cells?

Accepted Answer

Taxol stabilizes assembled microtubules, blocking disassembly and arresting mitosis; it also impairs axonal transport in neurons.

Question 8

A patient with progressive muscle weakness is found to have a mutation in the dystrophin gene. Which of the following best explains the cellular defect underlying this patient's symptoms?

Accepted Answer

Loss of dystrophin disrupts the link between the actin cytoskeleton and the extracellular matrix, leading to membrane fragility during muscle contraction.

Question 9

A researcher knocks out the gene encoding the enzyme responsible for adding mannose-6-phosphate to lysosomal hydrolases. Which of the following is the most likely cellular consequence?

Accepted Answer

Lysosomal hydrolases are synthesized but secreted extracellularly instead of being delivered to lysosomes.

Question 10

A cell is exposed to UV light, resulting in the formation of pyrimidine dimers in its DNA. Which DNA repair pathway is primarily responsible for correcting this damage, and what disease results if this pathway is defective?

Accepted Answer

Nucleotide excision repair; xeroderma pigmentosum.

Question 11

A patient with a mitochondrial myopathy is found to have a mixture of normal and mutant mitochondrial DNA in her muscle cells. What is the term for this phenomenon, and how does it explain the variable severity of her symptoms?

Accepted Answer

Heteroplasmy; the proportion of mutant to wild-type mtDNA determines the severity of the phenotype.

Question 12

A mutation in the gene encoding the U5 snRNP component PRPF8 leads to defective spliceosome assembly. Which of the following transcript-level outcomes is most likely in this scenario?

Accepted Answer

Both exon skipping and intron retention can occur, depending on which splice site recognition step fails.

Question 13

A cell is undergoing apoptosis. Which of the following best describes the change in membrane phospholipid distribution that occurs, and its functional consequence?

Accepted Answer

Phosphatidylserine is externalized to the outer leaflet, serving as an 'eat me' signal for phagocytes.

Question 14

A patient with ataxia telangiectasia has a defect in the ATM gene. Which step in the double-strand break repair process is primarily affected in this disease?

Accepted Answer

Recognition of double-strand breaks and activation of the DNA damage response.

Question 15

A cell is treated with a histone deacetylase (HDAC) inhibitor. Which of the following changes in chromatin structure and gene expression is most likely to occur?

Accepted Answer

Chromatin becomes more open (euchromatic), leading to increased gene expression.

Question 16

A mutation in the gene encoding the TATA-binding protein (TBP) would most directly impair which step of eukaryotic transcription initiation?

Accepted Answer

Binding of RNA polymerase II to the promoter via the TATA box.

Question 17

A patient with hereditary spherocytosis has fragile, spherical red blood cells. Which cytoskeletal protein is most likely mutated, and what is its normal function?

Accepted Answer

Spectrin; forms a network cross-linked to actin, maintaining RBC shape and flexibility.

Question 18

A cell is exposed to a PARP inhibitor. In which genetic background would this treatment be selectively lethal, and what is the underlying mechanism?

Accepted Answer

Cells deficient in BRCA1/2; loss of PARP-mediated single-strand break repair causes double-strand breaks that cannot be repaired by homologous recombination.

Question 19

A scientist is studying the role of the Pol II C-terminal domain (CTD) in mRNA processing. Which of the following best describes its function?

Accepted Answer

The CTD serves as a docking site for capping, splicing, and polyadenylation factors, coupling transcription to mRNA processing.

Cell Biology Exam 1 High-Yield Study Guide (Chapters 1–8)

Guida di studio - Domande di pratica

Study guide - Flashcard