Page 144 - Once Upon a Time There Was Darwinism

Once Upon a Time
There Was Darwinism

Hubert Renauld and Susan Gasser of the Swiss
Institute for Experimental Cancer Research comment that
despite heterochromatin's significant representation in the

genome (up to 15% in human cells and roughly 30% in flies), it has
often been considered as "junk DNA," of no utility to the cell. 85
But the latest studies have revealed that heterochromatin has
some important functions. Emile Zuckerkandl of the Institute of
Molecular Medical Sciences has this to say:
. . . [I]f one adds together nucleotides [DNA base pairs] that are individ-
ually nonfunctional, one may end up with a sum of nucleotides that are
collectively functional. Nucleotides belonging to chromatin are an ex-
ample. Despite all arguments made in the past in favor of considering
heterochromatin as junk, many people active in the field no longer
doubt that it plays functional roles. . . . Nucleotides may individually
be junk, and collectively, gold. 86
One of these "collective" functions of heterochromatin can be
seen in meiotic pairing. At the same time, studies of artificial chromo-
somes show that these segments of DNA have various functions. 87

3. Researchers have shown a relationship between non-coding
DNA and the cell nucleus—a development that spells the end of
the "junk DNA" concept.

A 1999 study examining the genomes of the single-celled photo-
synthetic organisms known as Cryptomonads discovered that eu-

karyotic non-coding DNA (also called secondary DNA) was
functional in the nucleus.
Characteristically, these organisms show a wide varia-
tion in size. But even if they are of varying dimensions,
there always remains a direct proportion between

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