What charge will histones have under physiological conditions? (b) Which type of amino acids must be present in large numbers in these proteins? (c) Why do you think that histones have this charge?

What charge will histones have under physiological conditions? Positive charge.

This is just something to be memorized: histones, the proteins that DNA wraps around to become tightly wound in physiological conditions, are positively charged. And I'll explain why shortly.

Which type of amino acids must be present in large numbers in these proteins? Positively charged amino acids.

It makes sense that some positive amino acids like arginine, histidine, and lysine would need to make up histones because histones are positive. There are probably neutral or noncharged amino acids as well.

Why do you think that histones have this charge? So they can bind/associate with negatively charged DNA.

The phosphate groups in the DNA backbone mean that DNA as a whole is negatively charged, so for histones to attract and not repel DNA, they need to be positive.