bio 250 final exam UPDATED ACTUAL Questions and
CORRECT Answers
What experiments demonstrated that DNA is the genetic Griffith's transformation experiment; Avery-MacLeod-McCarty identifying DNA as
material? transforming principle; Hershey-Chase using radioactive labeling to show only
phage DNA enters cells; Chargaff's base composition rules.
What is the structure of DNA? Two antiparallel strands in a double helix made of nucleotides with sugar-
phosphate backbones and internal A-T and G-C base pairs.
How is eukaryotic DNA packaged into chromosomes? DNA wraps around histones to form nucleosomes, condenses into chromatin, and
further coils into chromosomes.
How is chromosome structure regulated? Through chromatin-remodeling complexes and histone modifications that shift
regions between open (euchromatin) and closed (heterochromatin) states.
Why is base pairing essential? It stabilizes the helix and enables accurate replication and transcription.
Where does DNA replication begin? At replication origins where the DNA helix unwinds.
How many replication forks form at each origin? Two.
How does DNA polymerase synthesize DNA? By adding nucleotides complementary to the template strand.
Why is the replication fork asymmetrical? DNA polymerase can only synthesize 5'→3', leading to continuous leading-strand
and discontinuous lagging-strand synthesis.
How does DNA polymerase correct errors? Through its proofreading exonuclease activity.
Why are primers needed in replication? DNA polymerase cannot begin synthesis de novo; it requires an RNA primer.
What proteins cooperate at the replication fork? Helicase, primase, DNA polymerase, sliding clamp, ligase, and topoisomerase.
What types of DNA damage occur naturally? Depurination, deamination, oxidation, and UV damage.
What systems repair DNA damage? BER, NER, mismatch repair, and DSB repair pathways.
What does mismatch repair do? Removes base-pairing errors that escaped proofreading.
How are double-strand breaks repaired? By NHEJ (error-prone) or homologous recombination (error-free).
Why is homologous recombination accurate? It copies information from the intact sister chromatid.
What happens if DNA damage isn't repaired? Accumulation of mutations and potential disease.
What is the first step of the central dogma? Transcription.
CORRECT Answers
What experiments demonstrated that DNA is the genetic Griffith's transformation experiment; Avery-MacLeod-McCarty identifying DNA as
material? transforming principle; Hershey-Chase using radioactive labeling to show only
phage DNA enters cells; Chargaff's base composition rules.
What is the structure of DNA? Two antiparallel strands in a double helix made of nucleotides with sugar-
phosphate backbones and internal A-T and G-C base pairs.
How is eukaryotic DNA packaged into chromosomes? DNA wraps around histones to form nucleosomes, condenses into chromatin, and
further coils into chromosomes.
How is chromosome structure regulated? Through chromatin-remodeling complexes and histone modifications that shift
regions between open (euchromatin) and closed (heterochromatin) states.
Why is base pairing essential? It stabilizes the helix and enables accurate replication and transcription.
Where does DNA replication begin? At replication origins where the DNA helix unwinds.
How many replication forks form at each origin? Two.
How does DNA polymerase synthesize DNA? By adding nucleotides complementary to the template strand.
Why is the replication fork asymmetrical? DNA polymerase can only synthesize 5'→3', leading to continuous leading-strand
and discontinuous lagging-strand synthesis.
How does DNA polymerase correct errors? Through its proofreading exonuclease activity.
Why are primers needed in replication? DNA polymerase cannot begin synthesis de novo; it requires an RNA primer.
What proteins cooperate at the replication fork? Helicase, primase, DNA polymerase, sliding clamp, ligase, and topoisomerase.
What types of DNA damage occur naturally? Depurination, deamination, oxidation, and UV damage.
What systems repair DNA damage? BER, NER, mismatch repair, and DSB repair pathways.
What does mismatch repair do? Removes base-pairing errors that escaped proofreading.
How are double-strand breaks repaired? By NHEJ (error-prone) or homologous recombination (error-free).
Why is homologous recombination accurate? It copies information from the intact sister chromatid.
What happens if DNA damage isn't repaired? Accumulation of mutations and potential disease.
What is the first step of the central dogma? Transcription.
