OAT Cell and Molecular Biology 5

Question 1

Which mutation type results in the substitution of one amino acid for another without altering the reading frame?

Accepted Answer

Missense mutation

Answer

A missense mutation changes a single nucleotide so that a different amino acid is incorporated into the polypeptide chain.

Question 2

Which model best explains how pioneer transcription factors access nucleosome-occluded DNA?

Accepted Answer

They bind DNA within the nucleosome without full displacement

Answer

Pioneer factors like FOXA1 can engage their motifs within partially assembled nucleosomes, subsequently recruiting remodelers to open chromatin.

Question 3

The sodium-potassium ATPase transports ions against their concentration gradients in which stoichiometry?

Accepted Answer

3 Na⁺ out, 2 K⁺ in

Answer

Each cycle of the Na⁺/K⁺-ATPase exports 3 sodium ions and imports 2 potassium ions, consuming one ATP molecule.

Question 4

Which DNA repair pathway corrects mismatched bases introduced during DNA replication?

Accepted Answer

Mismatch repair (MMR)

Answer

Mismatch repair proteins (e.g., MutS, MutL homologs) recognize mismatched bases and excise a stretch of the newly synthesized strand for resynthesis.

Question 5

What distinguishes necrosis from apoptosis at the cellular level?

Accepted Answer

Necrosis involves cell swelling and membrane rupture; apoptosis is orderly with membrane blebbing

Answer

Necrosis is characterized by cell swelling and plasma membrane rupture causing inflammation, while apoptosis is an organized, caspase-dependent process producing apoptotic bodies.

OAT - Optometry Admission Test Practice Test

OAT - Optometry Admission Test Practice Test

OAT Cell and Molecular Biology 5