Question

What are DNase I hypersensitive sites?

a) Regions of DNA that are highly sensitive to the presence of DNase I
b) Sites where DNA is susceptible to damage by environmental factors
c) Regions of DNA where chromatin is less condensed and more accessible to DNase I
d) DNA areas resistant to enzymatic degradation

Answer 1

DNase I hypersensitive sites are areas of DNA where the chromatin is less condensed, making them susceptible to cleavage by DNase I and often associated with active gene regions.

Step-by-step explanation:

DNase I hypersensitive sites are regions in the DNA where the chromatin is less condensed, making these sites more accessible. These regions are particularly sensitive to cleavage by the enzyme deoxyribonuclease I (DNase I), which targets DNA strands. Unlike tightly packed chromatin such as heterochromatin, these hypersensitive sites are typically associated with active gene regions where transcription factors and other DNA-binding proteins can easily bind to DNA, indicating open chromatin that is actively being transcribed or regulated. Experiments have shown that DNA in these areas is degraded more rapidly by DNase I, signaling to researchers the locations where genes are most likely to be turned on, or "active". This is because DNA that is more actively transcribed is located in regions where the chromatin is less dense, allowing easier access to both DNase I and the transcription machinery. Overall, DNase I hypersensitive sites play a critical role in the regulation of gene expression by marking regions of the genome that are open for transcription and other DNA-related processes.