It's much closer to 98+%. The differences are very important however.

The difference between chimp and human when we look at single nucleotide substitution/differentiation (the differences in base pair by base pair) is a little less than 2%. Most of the differences being due to polymorphisms.

However, if you measure the difference on the basis of proteins across the ENTIRE population, we're only about 30% the same. On the other hand, nonsynonomous base pairs in protein coding regions (active DNA) put us over 98% the same. We share almost all of the same genes, but they are are expressed differently and to different degrees.

The main point here is, no matter HOW you look at it, chimps are our closest living relatives.

Another great thing to look at is endogenous retrogenes. Endogenous retroviral insertions are arguably the best example of molecular sequence evidence for universal common descent. Endogenous retrogene insertions are molecular remnants of a past parasitic viral infection. Occasionally, copies of a retrovirus genome are found in its host's genome, and these retroviral gene copies are called endogenous retroviral sequences. Retroviruses, like HIV, make a DNA copy of their own viral genome and insert it into their host's genome. If this happens to a germ line cell (i.e. the sperm or egg cells) the retroviral DNA will be inherited by descendants of the host. This process is rare and fairly random, so finding retrogenes in identical chromosomal positions of two different species indicates common ancestry.

There are at least seven different known instances of common retrogene insertions between chimps and humans, indicating common ancestry. I'll say it again, the same insertion occurs at the same DNA marker in two totally different species at a rate that is far far greater than chance. There are numerous know examples across other species as well.

This is one of my favorite articles on the subject:

Chimpanzee Sequencing and Analysis Consortium. 2005. Initial sequence of the chimpanzee genome and comparison with the human genome. Nature 437: 69-87.

http://www.nature.com/nature/journal/v437/n7055/full/nature04072.html;jsessionid=F75941597CD2465A06B19A3A4F411EDE

It is pointless to argue this if you don't understand how genes are expressed. As yellow pointed out the similarities are astounding showing us an obvoius ancestry. However, the disimilarites are extremely important as well. Old genes can learn new tricks. Neither of your co-workers understand genetics and the argument gets lost in tranlsation (hahahah get it? lost in TRANSLATION--HAHAHAH a..ahem..never mind).

I would like to add to this if I may. Retroviruses, specifically lentiviruses are being looked at as potential genetic therapeutical agents. The reason being is because they are able to insert themselves in a host's genome (provirus). This has huge implications when we're talking about faults in programmed cell death (apoptosis) at the genetic level such as a mutation in the p53 gene (like the Rb gene, is a tumor suppressor gene, i.e., its activity stops the formation of tumors, but when the gene malfunctions, then cells have the ability to keep growing without ever dying---ie..tumors/cancer).

If we can successfully alter retroviruses and add desired genes to target specific cancer cells. We could in theory kill tumor cells at the genetic level. In other words fix the mutated p53 gene in order for it to function properly and carry on with programmed cell death (apoptosis), killing the tumor.

It is ironic that this topic is being brought up now, because I just reviewed a protocol regarding lentiviral vector costructs as candidates for cancer treatment.

So on top of proving ancestry and evolution, retroviruses may also hold the key to eliminating cancer.

Any theists out there, that are reading this, I suggest you do not get treated with this new medicine if you do not believe in evolution, because we have essentially shown here that transposable elements (ie proviruses) prove evolution, therefore any medicine created from these viruses would in essence be linked to evolution, therefore, it is against your god...so I suggest you start praying instead of taking advantage of the hell sent therapy.

Absolutely. If they think the cure is immoral then we don't want them to 'dirty' themselves with science.
After all, their body is inconsequential. It's their 'soul' that they're worried about. lol.