which of these is more impotrtant in controlling cellular activities:
DNA or the proteins produced by it? Why?

Hello katecorey,

I would vote for the DNA being the most important.  Here is why:

Proteins do indeed provide the basis of cell function.  Some ways in
which they do this are: enzymes act as catalysts to enable biochemical
reactions; hormones, neurotransmitters and other "messengers" control
the responses of cells, tissues and organs.  However, the activity of
proteins depends on their structure and on how the protein molecules
fold themselves up (their conformation) and the way in which this
conformation changes in the course of their various reactions. 
Scientists have done experiments in which they "unfolded" a protein
and then let it fold up again.  They found that all the information on
how a protein should fold itself comes from the sequence in which
amino acids have been joined together to make the protein.  The
sequence of amino acids is determined by the sequence of nucleotides
on the part of the DNA which codes for the protein.  Changing even one
nucleotide in the sequence can result in a protein being produced that
does not do the job it is supposed to do, and this can sometimes
result in serious diseases (genetic disorders).

In summary, without DNA, there would be no proteins at all, since
there would be no blueprint from which to produce the proteins.  The
function of proteins depends on their structure, and their structure
depends on the structure of the DNA which acts as a blueprint for
them.

Here are some web sites with more information:
Here is a page with information about proteins and how their stucture
depends on DNA http://gslc.genetics.utah.edu/basic/protein.html
and here is quite a long article about protein folding:
http://www.faseb.org/opar/protfold/protein.html
Here is information about how the DNA is "read" to produce a protein:
http://gslc.genetics.utah.edu/basic/transcribe.html
and here is an animated sequence about the same topic:
http://www.agresearch.co.nz/scied/search/molecular/dnaexpress.htm
Here is a page about genetic diseases.  Halfway down it describes
single-gene disorders, which happen when the DNA of only one gene
coding for one protein becomes defective.  The page describes sickle
cell anaemia and gives links to other sites with information about
other single-gene disorders:
http://gslc.genetics.utah.edu/disorders/definition/index.html


Search strategy on Google: 1. proteins, structure;  2. proteins,
function

Good answer, Tehuti!

Tehuti said "In summary, without DNA, there would be no proteins at
all, since
there would be no blueprint from which to produce the proteins."

So how did life happen?  Without the DNA to produce the proteins out
of the "primordial soup", how did a cell form?  My bet would be a
CREATOR creating it.  The complexity of even the simplest single
celled organism is more than could ever happen accidentally. 
Evolution is a phony theory in which "scientists" ignore the tough
questions, and gloss over specifics.  Something to think about...

I would disagree with the answers provided to you. Proteins are now
thought to be involved in more cellular processes than ever before.
The new branch of proteomics actually is formed on this basis. For
every single gene there could be more than 10 gene products through
alternate mRNA slicing and post-translational modifications. Though
gene transcription is important cellular processes are more controlled
by phosphorylations of proteins to activate or inactivate regulatory
proteins. For example, cell cycle regulation is known to occur through
variety of protein-protein interactions controlling DNA replication.
Since this becomes a chicken and egg analogy, anyone could argue to
the contrary. But a more learned person would surely say protein.

Search Strategy: my MD + PhD curriculum

Sandybutt says:  "But a more learned person would surely say protein."

Hrm.  Dr. Tehuti is one of the most learned individuals I know.

Katecory, you've been given a terrific and well documented answer by
one of the many incognito professionals on the Researcher team.

Tehuti isn't just a Researcher.  She is actually a biomedical
scientist, Deputy Scientific Director of a renowned UK Research and
Education organization, and a well-known, respected member of her
profession.

I hope you find her answers as fascinating as I do - I've learned a
great deal from her.

--Missy  <--Researcher, and a Tehuti fan.

> Dr. Tehuti is one of the most learned individuals I know.  
I'm afraid I do have to disagree with her anyway.  Although I
absolutely would use this answer in response to the same question
asked by a non-biologist (as this one was), I have to say that
specifically "controlling cellular activities" is a function of the
proteins.  DNA of course encodes for the proteins, but the proteins
(widely read) are what receives and interprets environmental and
internal signals, and causes the cellular response (which may also
include increasing or surpressing transcription, but again this is a
protein mediated activity).

In some respects, it is a question of opinion - is the blueprint for
the car more important than the moving parts of the car when it comes
to getting to work?  But the essence of it, at least in my opinion, is
that the proteins are the more important of the two for controlling
cellular activities.

Yes, in the end it is a matter of totally subjective personal opinion.
My guess is that this was a homework assignment, and provided one
opinion or the other is presented with cogent arguments, it does not
really matter either way.  As an immunologist and toxicologist, I
still stand by my DNA vote.  I'm quite happy if others wish to argue
on behalf of proteins, provided that they supply documentary evidence
to back their claims.

I agree with you that your answer was quite appropriate for the
context of the question (although it does raise the question as to the
academic honesty of answering homework questions - I saw one question
posted here that was quite obviously from a graduate or advanced
undergraduate take home exam, and was fully researched and answered
for $100).

In terms of making a purely academic argument as for the primacy of
proteins in cellular control, though, I would say that you can view a
cell as a highly complex network of interlocking modules of
functionality, with the modules consisting themselves of networks of
biochemical interactions.  Stateful changes in the cell are executed
by activating signal cascades among these modules, which may alter the
proportion of active vs inactive molecules of particular species or
which may result in increased or decreased transcription of gene
products (which again may be seen as a change in the molecular
population).

So, we may view stateful changes in cellular molecular populations are
the essence of regulation of cellular activity.  These changes may
involve alteration of existing molecules, which changes ratios within
populations, or it may involve the transcription of new molecules.

For a stateful change that does not involve activation of a
transcription factor, we may say that the reaction occurs wholly among
the protein molecules.  For a change that involves transcriptional
regulation, we may still view the *product* of the reaction to be a
change in the overall molecular population, which is still protein
centric.  The important point is that DNA is only involved as one of
several vehicles for shifting between states, and that the states
themselves (a function of protein populations) are what "controls
cellular activities."

In terms of viewing proteins and netowrks or modules as computational
elements, Dennis Bray did a paper in 1994, and John Hopfield (of
Hopfield neural nets fame) has been advocating the use of the 'module'
paradigm in analysis of molecular biology, and has published several
reviews in (if I recall correctly) recent issues of Science and Nature
to that effect.  Sorry that I don't have the publication references
handy, but Bray's material is on his website and the Science and
Nature articles are on the journal's sites (Hopfield's site has only a
few papers).