Question

by dragging and dropping the descriptions from beneath the boxes into the appropriate column, sort the descriptions based on whether they increase or decrease transcription.
increase transcription decrease transcription
loosely coiled nucleosomes increase in dna methylation decrease in dna methylation
increase in histone acetylation decrease in histone acetylation tightly coiled nucleosomes

Explanation:

• Loosely coiled nucleosomes: When nucleosomes are loosely coiled, the DNA is more accessible to the transcription machinery (like RNA polymerase). This accessibility allows for easier binding and initiation of transcription, thus increasing it.
• Decrease in DNA methylation: DNA methylation (addition of methyl groups to DNA) usually acts as a repressive mark. A decrease in DNA methylation means that regions of DNA that were previously “silenced” (due to methylation) become more accessible. Transcription factors and RNA polymerase can bind more easily, increasing transcription.
• Increase in histone acetylation: Histone acetylation (addition of acetyl groups to histones) neutralizes the positive charge of histones. Since DNA is negatively - charged, less electrostatic interaction between histones and DNA occurs. This leads to a more relaxed chromatin structure (less tightly bound DNA - histone complex), making DNA more accessible for transcription, so transcription increases.
• Increase in DNA methylation: Methylated DNA is often associated with gene silencing. It can recruit proteins that compact the chromatin further or prevent the binding of transcription factors. So, an increase in DNA methylation decreases transcription.
• Decrease in histone acetylation: When histone acetylation decreases, histones retain their positive charge. This leads to a tighter interaction between histones (positively charged) and DNA (negatively charged), resulting in a more condensed chromatin structure. The transcription machinery has less access to the DNA, so transcription decreases.
• Tightly coiled nucleosomes: Tightly coiled nucleosomes mean that the DNA is less accessible. The transcription factors and RNA polymerase cannot bind easily to the DNA template, so transcription is decreased.

Answer:

• Increase transcription: Loosely coiled nucleosomes, Decrease in DNA methylation, Increase in histone acetylation
• Decrease transcription: Increase in DNA methylation, Decrease in histone acetylation, Tightly coiled nucleosomes