Now look at the article. http://en.wikipedia.org/wiki/Chromosome
It's not so bad. It even helpfully glosses some of the technical terms like 'mitosis' and 'histone'.
If you don't already know what DNA and genes are then you probably need to read about those terms first. Both articles are about as accessible to laymen as I would expect in an encyclopaedia.
I'm not saying it's impossible to do better but from my point of view most readers of these articles will already have a basic familiarity with genetics / molecular biology. To those readers wading through an explanation of all terms from first principles (which are what? what knowledge of biology and chemistry should we assume?) in each article would be tiresome.
I agree that we should try to be accessible. And indeed the chromosome article could probably be improved. Britannica's article starts with this definition:
"Microscopic, threadlike part of a cell that carries hereditary information in the form of genes."
That's probably more helpful to newbies than:
"A chromosome (in Greek chroma = colour and soma = body) is, minimally, a very long, continuous piece of DNA, which contains many genes, regulatory elements and other intervening nucleotide sequences."
I'm not saying you're wrong but I'm slightly worried that the guideline/policy/project could go overboard. As long as all changes to articles are information-preserving then I wish you good luck.
Regards, Haukur