Re: How are genes counted in Human Genome Project?



"IRR" iotarhorho@xxxxxxxxxxxxxxxxx wrote:-
JE:-
To be CORRECT any segment that is deemed "one gene" has to code for
one
polypeptide and NOT one protein. Almost all proteins are complex
combinations of MORE than just one polypeptide which means that at
the
very
least MORE than one gene is almost always required to code for ONE
protein.
In biological terms, the enormous difference between a polypeptide
and
a
protein (which remains glossed over within gene centric theory only
because
it is inconvenient) places genetic epistasis at the forefront of
SYNTHETIC
genetics and not on just the backburner where it has been languishing
ever
since Fisher et al.

This is in part correct, but is also part incorrect or else easily
misinterpreted:
-A single gene most certainly can encode a single protein, which may or
may
not be a subunit in a protein complex.

JE:-
Polypeptides and proteins only differ in SIZE, i.e. they differ in
degree
and not in kind.

No. See any basic biochemistry text.

JE:-
Such rhetoric depends on the _credibility_ of you failing to provide a
text...

Wikipedia:

http://en.wikipedia.org/wiki/Polypeptides

"Proteins are polypeptide molecules (or consist of multiple polypeptide
subunits). The distinction is that peptides are short and proteins are long.
There are several different conventions to determine these, all of which
have flaws. In order for a polypeptide to be a protein it has to have some
sort of biological function in the body".

"Another convention places an informal dividing line is at approximately 50
amino acids in length (some people claim shorter lengths). However, this
definition is somewhat arbitrary - some peptides such as alzheimer's beta
peptide can be considered proteins and some proteins (such as insulin) are
close to the upper limit for peptides. Because of the arbitrary nature of
this definition, there is considerable movement within the scientific
community to ascribe the more-specific definition that "a peptide is an
amino acid molecule without secondary structure; on gaining defined
structure, it is a protein." "

As I stated in my previous post the difference between a polypeptide and
protein remains ARBITRARY.


Empirically, the vast majority of proteins "in vivo" consist of MORE
than
just the one polypeptide (of course this does not apply to "in vitro"
proteins which however only represent biochemical SIMPLIFIED MODELS of
proteins. Indeed, I do not know of a single "in vivo" protein which
consists of just one polypeptide. Perhaps you could enlighten us and
provide
an example?

Again, no. PiP provided a perfectly valid example -- cytochrome c
(variants
of which are often several hundred amino acids long,,

JE:-
As the online Wikipedia reference has confirmed, the relatively shorter
chains are mostly referred to as polypeptides.

The view: "one gene one polypeptide" has become a useful empirical measure
of "one gene". Here all non coding genes are excluded from being a gene.
Using such a definition almost all body proteins become combinations of MORE
than just one coding gene product. IOW genetic epistasis (and therefore NON
additive and not just additive gene fitnesses) entirely dominates the
fitness of almost any protein's architecture.

As discussed, any difference between a polypeptide and protein remains
ARBITRARY. IOW, no matter what you define any particular amino acid chain to
be, the theory of protein synthesis stands refutable but _non_ refuted. A
change in the definition of a polypeptide to be a protein or vice verses can
only produce a non verification which is not a refutation. Any non
verification remains non definitive for the theory non verified.

Snip<

Regards,

John Edser
Independent Researcher

edser@xxxxxxxxxxxxxx


.

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