I read posts where human DNA is compared  to be 98% (or so) similar to the DNA of a chimpanzee.

For comparison, how does human DNA compare to that of  other species: for example to that of a  mouse, a horse , or dog, or worm ,or fruit-fly, or a banana, or whatever?

By memory;  I think a fruit fly has 50% similar DNA to  a human
Dogs 75%
Banana 30 %

Are these %s correct?

A deceptively simple question that is actually very hard to answer meaningfully! It really depends on what you mean by comparing DNA of one species to another. If you mean directly comparing the whole of one genome to another then the figures for similarity are very low, if you mean the similarities between the genes that code for proteins then the figure is very high! Don't forget that the vast majority of mammalian DNA does NOT code for proteins it was at one point thought to be "junk DNA" though we now realise it all has a role to play - we are just not entirely sure of the details yet.

The link below is an excellent place to start reading about these subjects:-

http://www.ornl.gov/sci/techresources/H … pgen.shtml

also do browse some of the previous questions in the forum that have asked related questions