AAMC MCAT Biological and Biochemical Foundations 2 — Questions and Answers
Question 1: During which phase of mitosis do chromosomes align at the equatorial plate?
- Metaphase (Correct answer)
- Prophase
- Anaphase
- Telophase
Correct answer: Metaphase
During metaphase, chromosomes align along the metaphase plate so spindle fibers can attach to kinetochores for proper segregation.
Question 2: What does the lac operon repressor do when lactose is absent?
- Binds the operator and blocks transcription (Correct answer)
- Activates RNA polymerase
- Degrades remaining lactose
- Promotes translation of structural genes
Correct answer: Binds the operator and blocks transcription
Without lactose, the repressor binds the operator region, physically preventing RNA polymerase from transcribing the structural genes.
Question 3: Which chemical bond connects nucleotides in a DNA strand?
- Phosphodiester bond (Correct answer)
- Hydrogen bond
- Peptide bond
- Ionic bond
Correct answer: Phosphodiester bond
Phosphodiester bonds link the 3' carbon of one nucleotide's sugar to the 5' phosphate of the next, forming the DNA backbone.
Question 4: Where does the TCA (Krebs) cycle take place in eukaryotic cells?
- Mitochondrial matrix (Correct answer)
- Inner mitochondrial membrane
- Cytoplasm
- Outer mitochondrial membrane
Correct answer: Mitochondrial matrix
TCA cycle enzymes reside in the mitochondrial matrix, where acetyl-CoA is oxidized to CO2 with production of NADH and FADH2.
Question 5: What is the function of telomerase?
- Extends telomeres to prevent chromosome shortening during replication (Correct answer)
- Initiates DNA replication
- Repairs double-strand DNA breaks
- Removes Okazaki fragment RNA primers
Correct answer: Extends telomeres to prevent chromosome shortening during replication
Telomerase adds repetitive sequences to chromosome ends, preventing the progressive shortening that would otherwise occur with each replication cycle.
Question 6: Which mutation type shifts all downstream codons by inserting or deleting nucleotides?
- Frameshift mutation (Correct answer)
- Missense mutation
- Nonsense mutation
- Silent mutation
Correct answer: Frameshift mutation
Frameshift mutations alter the reading frame for all downstream codons after the insertion or deletion, typically producing a nonfunctional protein.
AAMC MCAT Biological and Biochemical Foundations 2
During which phase of mitosis do chromosomes align at the equatorial plate?