[Campbell Biology P.426] According to the 'Nuclear Architecture and Gene Expression' section... | Practice Question

According to the 'Nuclear Architecture and Gene Expression' section, which of the following statements about gene organization within the nucleus is correct?

  • A: All chromosomes randomly occupy any space within the nucleus, leading to a 'spaghetti' model.
  • B: Expressed genes tend to be located in the interior region of the nucleus, often within 'transcription factories'.
  • C: Unexpressed genes are actively moved to the interior region of the nucleus for transcription.
  • D: Topologically associated domains (TADs) are dynamic structures that ensure chromatin sites associate randomly.

Explanation

The section 'Nuclear Architecture and Gene Expression' describes a modern understanding of nuclear organization. It states that 'unexpressed genes are located in the outer edges of the nucleus, while those that are being expressed are found in its interior region.' It further explains that loops of chromatin can extend into 'transcription factories,' which are 'areas specialized for a common function,' including being 'rich in RNA polymerases and other transcription-associated proteins.' This indicates that expressed genes are primarily found in the interior, often within these transcriptionally active zones.