I was midway through my post when I realized, there may be a misunderstanding. When I said if you score under a 19, your chances drop significantly, I was referring to the AA not just the Biology score specifically. However, if we use the TS scores to do the calculation, we can get a somewhat better representation. Anyway, take this with a grain of salt but have a look.
Based on the statistics here:
http://forums.studentdoctor.net/showthread.php?t=901073
These are for 2009 enrollees, but I can't imagine the trend being any different, if anything the % of getting accepted with a 19 or under AA is even lower since DAT scores are going up. Doc Toothache doesn't have the averages for the most recent class, and I've already sold my ADEA book.
But, if you have a look at the table at the bottom. With a DAT AA score of 19-20, your acceptance rate is about 58.8% (3492 applicants, 2056 accepted). However, when you drop down to a 17-18 DAT, acceptance rate is 34.24%. This is a 24% drop, compared to say dropping from a 21 to the 19-20 range, which is only about 14%, so that's double. Doing the same thing with TS because of the reason explained above, a TS of 19-20 has a acceptance rate of 56.3% (3480 applicants, 1958 accepted), compared to under 19, 34.5%. Again, we see a 22% drop. Now, do take this with a grain of salt because these are overall averages (AA and TS) that combines more than one section, so your doing poorly in one section will probably not have such an ill effect... but I can't imagine this trend not applying to individual scores as well in terms of acceptance chance, even if it's not a staggering 25%. Something to think about.
Again, I am really happy to hear Iaa being accepted with a below average DAT score, but this is absolutely not the norm. I would considering him an outlier, albeit not an extreme. Take this for what it's worth... Again, I am not trying to be hostile towards Iaa, but I see way too often people saying "Oh you're fine" "Just apply and give it a try" "You can do it" etc. etc. giving people false hope and not retaking the DAT, or doing a Masters or the sorts when they really should to increase their chances. Again, whether you take the DAT again is up to you. You absolutely do have a chance as is... but is it worth the risk in time and money to have to re-apply if you don't get in...? Well, only you can answer that. One last thing to note is that applications ARE viewed holistically, so I am not taking into consideration other factors, just purely your DAT score.