How does chromosome condensation affect gene expression in eukaryotic cells?

• A. Chromosome condensation only affects gene expression during DNA replication, not transcription.
• B. Highly condensed chromatin generally reduces gene expression by limiting access of transcription machinery.
• C. Condensation of chromosomes has no effect on gene expression.
• D. Chromosome condensation always increases gene expression by exposing promoter regions.

Answer: (B)

Verified step by step guidance

1. Understand that chromosome condensation refers to the process by which chromatin fibers become tightly packed into a more compact structure, especially during certain phases of the cell cycle.
2. Recognize that gene expression requires access to DNA by transcription machinery, such as RNA polymerase and transcription factors, which bind to promoter and regulatory regions of genes.
3. Know that highly condensed chromatin, often called heterochromatin, is generally less accessible to transcription machinery, leading to reduced gene expression.
4. Contrast this with less condensed chromatin, or euchromatin, which is more open and accessible, allowing active transcription and higher gene expression.
5. Conclude that chromosome condensation typically reduces gene expression by physically limiting the accessibility of DNA to the transcriptional machinery, rather than increasing it or having no effect.