Explain why dna has an overall negative charge.

 DNA has an overall negative charge because DNA backbones are made of deoxyribose and pentose sugar which are connected in phosphodiester bond. The groups of phosphate usually have a negative charge that makes positively charged particles (histone proteins) to interact and form chromatin.

answer: - b cells

explanation: -

there are many types of white blood cells present in our body. one such class of white blood cells are the lymphocytes. the b cells belong to the lymphocyte class of wbcs. the b cells perform their action against the pathogen by producing specialised proteins called as antibodies. these antibodies are produced as and when the b cells encounter pathogens in response to the antigens present on the surface of the pathogen. these antibodies bind to the antigens present on the pathogen and then, target them for destruction by other cells of the immune system.

so, the b cells mediate their action by identifying the antigens present on the surface of the pathogens and then producing antibodies in return to mediate its effect.