What would happen if our atmosphere consisted of pure oxygen?

You mean, biologically? There would be no life, at least not as we know it. Plants need carbon dioxide. I suppose an ecosystem composed entirely of animals might be possible. But animals produce CO2, methane, and a host of other off-gases. So your hypothetical planet would be populated by things very different from us. 

Well too much oxygen can kill humans which is one. And 2 If the whole atmosphere was oxygen then things will burn easily.

The short-term effect of tar on the body is increased blood pressure.

The main role of dna in the  cell is the long-term storage of information. it is often compared to a blueprint, since it contains the instructions to construct other components of the  cell, such as  proteins  and rna molecules.the main function of rna is to carry information of amino acid sequence from the genes to where  proteins  are assembled on  ribosomes  in the  cytoplasm. mark brainliest, my work is good.