Question

Each answer box represents a mechanism by which eukaryotes normally regulate gene expression. Determine which of the five mechanisms each example represents. Not all examples will be used. Five mechanisms: changes in chromatin structure activity of transcription apparatus RNA processing RNA interference initiation of translation Gene inversion does not cause a loss of genetic info but may affect regulation of the inverted genes. A siRNA and the transcript it targets are transcribed from the same gene. Methylation of CpG islands represses promoter activity. Limited availability of initiation factors prevents translation of mRNA Transcriptional repressors compete with activators for DNA binding sites. The 3' end can be cleaved to produce different transcript lengths before addition of the poly-A tail.

Answer 1

The student's examples represent various mechanisms of gene regulation in eukaryotes: methylation affecting chromatin structure, transcriptional repressors affecting transcription apparatus activity, cleavage at the 3' end illustrating RNA processing, siRNA indicating RNA interference, and availability of initiation factors relating to the initiation of translation.

Step-by-step explanation:

The examples provided by the student represent different mechanisms by which eukaryotes regulate gene expression:

• Changes in chromatin structure: 'Methylation of CpG islands represses promoter activity' corresponds to changes in chromatin structure as DNA methylation typically leads to a more condensed chromatin state, making the DNA less accessible for transcription.
• Activity of transcription apparatus: 'Transcriptional repressors compete with activators for DNA binding sites' is an example of the activity of the transcription apparatus where proteins interact with promoter or enhancer regions to regulate the initiation of transcription.
• RNA processing: 'The 3' end can be cleaved to produce different transcript lengths before addition of the poly-A tail' exemplifies RNA processing, where the pre-mRNA is modified to create different versions of the mRNA that can lead to different proteins.
• RNA interference: 'A siRNA and the transcript it targets are transcribed from the same gene' indicates RNA interference, which involves siRNA in the degradation or silencing of target mRNA transcripts.
• Initiation of translation: 'Limited availability of initiation factors prevents translation of mRNA' is associated with the initiation of translation, where protein synthesis can be controlled by the availability of factors required for the process to start.

Answer 2

Gene inversion, siRNA and transcript, Methylation of CpG islands, Limited availability of initiation factors, Transcriptional repressors, Cleaving of 3' end

Step-by-step explanation:

Gene inversion does not cause a loss of genetic info but may affect regulation of the inverted genes. A siRNA and the transcript it targets are transcribed from the same gene. Methylation of CpG islands represses promoter activity. Limited availability of initiation factors prevents translation of mRNA. Transcriptional repressors compete with activators for DNA binding sites. The 3' end can be cleaved to produce different transcript lengths before addition of the poly-A tail.

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