An investigator is comparing DNA replication in prokaryotes and eukaryotes. He finds that the entire genome of E. coli (4 × 106 base pairs) is replicated in approximately 30 minutes. A mammalian genome (3 × 109 base pairs) is usually replicated within 3 hours. Which of the following characteristics of eukaryotic DNA replication is the most accurate explanation for this finding?
AReplication inhibition at checkpoint
BAbsence of telomerase enzyme activity
CDNA compaction in chromatin
DSimultaneous replication at multiple origins
EMore efficient DNA polymerase activity
A 71-year-old man with colorectal cancer comes to the physician for follow-up examination after undergoing a sigmoid colectomy. The physician recommends adjuvant chemotherapy with an agent that results in single-stranded DNA breaks. This chemotherapeutic agent most likely has an effect on which of the following enzymes?
ADNA polymerase III
BTopoisomerase I
CHelicase
DTelomerase
ETopoisomerase II
A 3-year-old male child is found to have a disease involving DNA repair. Specifically, he is found to have a defect in the endonucleases involved in the nucleotide excision repair of pyrimidine dimers. Which of the following is a unique late-stage complication of this child's disease?
ATelangiectasia
BColorectal cancer
CMalignant melanoma
DLymphomas
EEndometrial cancer
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