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.