Identifying Accurate Cellular Structure Descriptions

Steps:

• Recall standard definitions: centromere links sister chromatids until anaphase and binds spindle fibers in prometaphase; chromatid is a replicated chromosome arm of DNA and proteins; nucleolus is an eukaryotic rRNA site, absent in prokaryotes; telomere is protective repetitive DNA at chromosome ends.
• Assess A: centromere timing and attachment are incorrect.
• Assess B: chromatid definition holds but phrasing implies only two parts total, overlooking full chromosome context.
• Assess C: nucleolus is eukaryotic, not prokaryotic.
• Confirm D: matches telomere as repetitive end-sequence on chromatids.

Why D is correct:

• Telomeres are defined as short, repetitive DNA sequences (e.g., TTAGGG in humans or GGGTTA variants) at linear chromosome ends to prevent degradation.

Why the others are wrong:

• A: Centromere holds chromatids until anaphase, not prophase; spindle attachment occurs in prometaphase.
• B: Chromatids form post-replication; description inaccurately simplifies chromosome as only two parts.
• C: Nucleolus exists only in eukaryotic nuclei for ribosome assembly; prokaryotes lack it.

Final answer: D