[BigRedBeta]

If the DNA sequence in humans is so close to that of chimpanzees, why do the two species look so different?"

You're very correct in the issue of differences of gene promotion.

Sequence is only one part of the equation. The ways in which an individual gene is turned on - in terms of frequency, timing, and so forth - accounts for a great deal of the variety. Further, because genes have effects on other genes down the line, turning them on and off in particular sequences (accomplished through a variety of promoter and inhibitor sequences in front and behind a particular gene), matters as well.

Think of it this way. Say you have a number of red, blue and green legos. For one building, you start out with 50 red pieces, 20 blue pieces, and 30 green pieces. No matter what you build, from a color stand point, it's going to look MUCH different than the thing you build with 10 red pieces, 75 blue pieces and 15 green pieces. DNA in the fact that it essentially codes for those building blocks (proteins) is very similar.

Well, if chimps and humans are so close in DNA and chromosome number, what if we were to use the science of In vitro fertilization. Would something come from it?

Would likely depend on what's encoded on that extra set of chromosomes, and how well a fertilization would respond to that missing set of information. As far as humans go, monosomies are poorly, poorly tolerated and result uniformly in spontaneous abortion of the pregnancy. There are only three human Trisomies (having three of a particular set of chromosome) that result in a fetus compatible with extra-uterine life - 13 http://en.wikipedia.org/wiki/Patau_syndrome ; 18 - http://en.wikipedia.org/wiki/Edward%27s_Syndrome ; and 21 - which is Down's syndrome. Edwards and Patau syndrome infants rarely live past a year. And yet, obviously Down's syndrome has a pretty variable prognosis and many individuals live long, fulfilling lives. So it's difficult to predict exactly what you're cross breeding experiment would beget.