March 26, 2005

the great banana debate

If you're late to this, it started last week when I posted a video showing how bananas naturally divide into 3 sections.

Then a reader named Em wrote to me, dropping some science about why bananas do that. Another reader named Kirsty wrote in questioning Em's facts and a small science debate erupted.

Since then Kirsty has written back on the comment board retracting a couple of her initial statements and now all is well (even though other debates continue to be popping up in there.)

Before Kirsty posted again to smooth things out, I received two really sassy science responses from Em. Everthing is cool now between our new pals, but I'd still like to post Em's two emails to me because they amused me so.

Who doesn't enjoy a fired-up science chick? (And my wife says it's a pleasant diversion from my usual wiener jokes.)

email #1:

okay, so let me get this straight ... a banana divides into three parts because it has three chromosomes where there should be two? oh, i get it ... trisomy. ha ha. so that must mean a banana with the "usual" two chromosomes would split into two pieces instead of three? that's almost too cute. cute, but wrong. check your sources, dear. try a plant anatomy text book. look up "carpel." you will find that when a plant ovary is made up of several of these "carpel" units, it has individual comparments called locules. the banana is splitting along the lines of these separate compartments.

i am not going to debate the number of chromosomes a banana possesses because, frankly, i don't really give shit. maybe there are three chromosomes where there should be two. maybe not. however, whether or not that is true, that is NOT why bananas split into three wedges.

em


followed up quickly by...

hi there -- me again --

so, i decided that before i make a complete ass of myself, i should check my sources. turns out, our friend kristy should have done the same.

bananas are not a trisomy as kirsty claimed. a trisomy refers to the addition of a single chromosome in the entire set. note: down's syndrome is a trisomy because individuals with down's syndrome have an extra 21st chromosome (you will also note that kirsty told us [incorrectly] that down's syndrome was the result of a missing chromosome ... rubbish!)

back to bananas: the bananas that we buy in the grocery store are triploid organisms, which means that they have three entire sets of chromosomes. not just one extra chromosome. how do they get that extra set of chromosomes, you ask? well let's go back to what i said initially "...and clever beings that we can be, we have horticulturally modified the bananas to have very tiny seeds." (remember when i said that?) that's right, boys and girls, bananas in grocery stores are triploid because they are human modified. they do not occur that way in nature, and their chromosomes did not "get screwed up" so they can't reproduce. People actually bred a banana plant that had two sets of chromosomes (a diploid) with a banana plant that had four sets of chromosome (a tetraploid) and voila! triploid bananas.

so i guess i too, must disagree with a point made. and to kirsty, i say, "you better back that train up a bit more."

em

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