Question

The DNA sugar phosphate structure carries an overall negative charge due to the pKa of one of the phosphate groups being much less than physiological pH, and another very close to physiological pH. What overall charge do histones carry on their surface?A. negativeB. positiveC. No answer text provided.

Answer 1

Answer:

B. positive

Explanation:

Histones are proteins that bind to the DNA in order to form highly compacted structures named nucleosomes, the basic structural units of DNA packaging in eukaryotic genomes. A nucleosome is a segment of DNA wound around an octamer (8) of histones, i.e., two copies each of the histones H2A, H2B, H3, and H4. These histones are positively charged in order to interact with the negatively charged DNA molecule. During transcription, reducing histone positive charge decreases the interaction between DNA and histones in the nucleosomes, thereby opening the chromatin to favor the access of the transcriptional complex and thus facilitates gene expression.