Select the true statements describing eukaryotic and prokaryotic nucleic acid structure and function? (Select all that apply)

Question

BlackTom AI · Accepted Answer

Operons are common in prokaryotes, so statement a is correct: prokaryotic genes are often organized in operons (clusters of adjacent genes transcribed as a single polycistronic mRNA under shared regulation, e.g., the lac operon), whereas eukaryotic genes are typically monocistronic (each gene has its own promoter and is transcribed separately).

1) Relevant knowledge points and concepts
- Operons: common in bacteria; allow coordinated expression of functionally related genes.
- Transcription factors: proteins that regulate transcription in both domains, though types differ (bacterial regulators and sigma factors vs. eukaryotic general and specific transcription factors).
- Histones and nucleosomes: canonical nucleosomes (H2A, H2B, H3, H4 wrapped by ~147 bp DNA) are a defining feature of eukaryotic chromatin.
- Replication origins: eukaryotic linear chromosomes are large and use multiple replication origins; most bacterial circular chromosomes use a single origin (oriC).

2) Step-by-step reasoning to evaluate each option
a) Operons: True. Bacterial operons are textbook examples; eukaryotes usually do not organize genes this way.
b) “Only eukaryotes have transcription factors”: False. Bacteria have transcriptional regulatory proteins and sigma factors that functionally act as transcription factors.
c) “Both eukaryotes and prokaryotes have histones organized into nucleosomes”: False in the general sense. Eukaryotes have canonical histones forming nucleosomes. Most bacteria lack histones/nucleosomes. (Note: some archaea—prokaryotes—have histone-like proteins, but these are not the canonical eukaryotic nucleosome structures; the statement as written is incorrect.)
d) Multiple origins: True. Eukaryotic chromosomes contain many origins of replication to replicate large genomes quickly; most prokaryotic chromosomes have a single origin (with exceptions like multipartite genomes or some bacteria with multiple origins, but the general rule stands).

3) Calculations
- None required.

4) Why the correct answers are correct
- a is correct because operon structure and polycistronic transcription are characteristic of bacteria.
- d is correct because eukaryotic genome size and linear chromosome structure necessitate multiple replication origins; bacteria typically replicate from a single origin.

5) Why the other options are incorrect
- b is incorrect: prokaryotes do have transcription regulators (including sigma factors).
- c is incorrect: canonical histone-based nucleosomes are a eukaryotic feature; most bacteria lack them (archaea aside).

Conclusion: The true statements are a and d, which matches the provided answer.

Select the true statements describing eukaryotic and prokaryotic nucleic acid structure and function? (Select all that apply)多项选择题

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