Question

A number of experiments have demonstrated that areas of the genome that are transcriptionally inactive are also resistant to dnase i digestion. however, transcriptionally active areas are dnase i sensitive. describe how dnase i resistance or sensitivity might indicate transcriptional activity.

a. when dna is transcriptionally inactive, it is in a less condensed state and as such, less open to dnase digestion.
b. when dna is transcriptionally active, it is in a more condensed state and as such, more open to dnase digestion.
c. when dna is transcriptionally active, it is in a less condensed state and as such, more open to dnase digestion.
D. the condensation state does not affect resistance to dnase digestion. resistance depends on the presence of specific methylation markers.

Answer 1

DNase I sensitivity indicates transcriptional activity as active DNA in euchromatin is less condensed, making it more exposed and susceptible to DNase I digestion compared to the inactive, condensed heterochromatin, which is resistant.

Step-by-step explanation:

DNase I sensitivity can indicate transcriptional activity. When DNA is transcriptionally active, it is often found in a less condensed state known as euchromatin. This open conformation allows transcription machinery to access the DNA, and hence such regions are more susceptible to DNase I digestion. In contrast, transcriptionally inactive DNA is typically more condensed into heterochromatin, making it resistant to DNase I because the DNA is tightly packed and surrounded by proteins, which protect it from enzymatic attack. Modifications such as DNA methylation and histone modification can affect nucleosome spacing, influencing the chromatin state and thus the transcriptional activity. For example, acetylation of histones can open up the chromatin, while methylation can have varying effects, sometimes silencing the gene.

The correct answer that describes how DNase I resistance or sensitivity might indicate transcriptional activity is: C. When DNA is transcriptionally active, it is in a less condensed state and as such, more open to DNase digestion.