Cell and Molecular Biology Flashcards
7 cards from real OAT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Cell and Molecular Biology flashcards as text
Which mutation type results in the substitution of one amino acid for another without altering the reading frame?
Answer: Missense mutation
A missense mutation changes a single nucleotide so that a different amino acid is incorporated into the polypeptide chain.
Which model best explains how pioneer transcription factors access nucleosome-occluded DNA?
Answer: They bind DNA within the nucleosome without full displacement
Pioneer factors like FOXA1 can engage their motifs within partially assembled nucleosomes, subsequently recruiting remodelers to open chromatin.
The sodium-potassium ATPase transports ions against their concentration gradients in which stoichiometry?
Answer: 3 Na⁺ out, 2 K⁺ in
Each cycle of the Na⁺/K⁺-ATPase exports 3 sodium ions and imports 2 potassium ions, consuming one ATP molecule.
Which DNA repair pathway corrects mismatched bases introduced during DNA replication?
Answer: Mismatch repair (MMR)
Mismatch repair proteins (e.g., MutS, MutL homologs) recognize mismatched bases and excise a stretch of the newly synthesized strand for resynthesis.
What distinguishes necrosis from apoptosis at the cellular level?
Answer: Necrosis involves cell swelling and membrane rupture; apoptosis is orderly with membrane blebbing
Necrosis is characterized by cell swelling and plasma membrane rupture causing inflammation, while apoptosis is an organized, caspase-dependent process producing apoptotic bodies.
Which small non-coding RNA class guides Argonaute proteins to silence target mRNAs post-transcriptionally?
Answer: miRNA
microRNAs (miRNAs) associate with RISC (RNA-induced silencing complex) and base-pair with complementary sequences in target mRNA 3' UTRs to repress translation or promote degradation.
Which property of the plasma membrane is primarily responsible for its selective permeability to small nonpolar molecules?
Answer: The hydrophobic lipid bilayer core
Small nonpolar molecules dissolve readily in the hydrophobic interior of the bilayer and diffuse across without requiring protein channels.