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Question about DNA
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elgoog
medicine forum Guru


Joined: 28 Apr 2005
Posts: 412

PostPosted: Wed May 25, 2005 9:57 am    Post subject: Re: Question about DNA Reply with quote

Kumar wrote:
Quote:
Hello,

I want to know:-

Whether DNA of different person is a structural/arrangement change or a
chemical composition change? I mean that, if DNA of different person
can be different in structure/arrangement or in chemical changes?

If it is only structural/arrangement change, how it can create so many
differenciating features in different individuals?

This link tells somewhat structural/sequence change.
http://en.wikipedia.org/wiki/DNA

Best wishes.

I don't think I am understanding your question. The structural
arrangement of the DNA is defined by the chemical composition.
Different features and different creatures are created by differences
in the chemical composition.
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Jeff
medicine forum Guru


Joined: 25 Mar 2005
Posts: 1313

PostPosted: Wed May 25, 2005 10:08 am    Post subject: Re: Question about DNA Reply with quote

"Kumar" <lordshiva5753@rediffmail.com> wrote in message
news:1117007586.284158.168480@g44g2000cwa.googlegroups.com...
Quote:
Hello,

I want to know:-

Whether DNA of different person is a structural/arrangement change or a
chemical composition change? I mean that, if DNA of different person
can be different in structure/arrangement or in chemical changes?

If it is only structural/arrangement change, how it can create so many
differenciating features in different individuals?

This link tells somewhat structural/sequence change.
http://en.wikipedia.org/wiki/DNA

Best wishes.

All the DNA that carries our genetic code is in the form of a double helix.
What is different from person to person is the sequence of the bases (ACGT).
However, it is all in the form of a double helix.

So there are different sequences, but all of this is in the double helix, so
it has the same structure, but a different sequence.

Jeff
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Kumar
medicine forum Guru


Joined: 10 May 2005
Posts: 870

PostPosted: Thu May 26, 2005 7:16 am    Post subject: Re: Question about DNA Reply with quote

I mean; whether chemical formula of all DNA in a person & of different
human beings are same or not and if its structural formulas are
different?
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Kumar
medicine forum Guru


Joined: 10 May 2005
Posts: 870

PostPosted: Thu May 26, 2005 7:28 am    Post subject: Re: Question about DNA Reply with quote

Thanks, I want to know; whether total numbers of bases(ACGT) are same
in DNA of all or most of human beings resulting in same chemical
formula of All DNA in all human beings or not? Whether chemical formula
of all DNA in all or most human beings are same but their structural
formula can be different or not?
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elgoog
medicine forum Guru


Joined: 28 Apr 2005
Posts: 412

PostPosted: Thu May 26, 2005 11:05 am    Post subject: Re: Question about DNA Reply with quote

Kumar wrote:
Quote:
I mean; whether chemical formula of all DNA in a person & of different
human beings are same or not and if its structural formulas are
different?

You must still be toying with an idea that you haven't yet expressed.
I'm not sure what that idea is, but maybe this will help? The
differences are caused not only by differences in sequencing, but also
by omissions or the addition of extra sequences. Thus, I would not
expect each person to have the exact same number of pairings, though I
would expect each DNA molecule to conform to the same structural
integrity.

Nonetheless, mutations are frequent and apparently more often
meaningless rather than significantly harmful or beneficial.

I doubt that whatever you are pondering can be answered this
simplisticly, but I suppose it is possible you are merely overlooking
the obvious. OTOH, you may be thinking about something totally new....
You might be interested in the human genome project? There are about 3B
base pairs (that is an approximation and some individuals may have
slightly less or slightly more).

Humans can be so different, that we can actually vary in the number of
bones we have. At birth, we average 275 bones, as we grow bones fuse
leaving on the average 206 bones in the adult, but not always. If there
can be a variance between us on a scale of 206-275, imagine how much
variance might occur with approximately 3B pairings.
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Jeff
medicine forum Guru


Joined: 25 Mar 2005
Posts: 1313

PostPosted: Thu May 26, 2005 5:38 pm    Post subject: Re: Question about DNA Reply with quote

"Kumar" <lordshiva5753@rediffmail.com> wrote in message
news:1117099730.489671.78210@o13g2000cwo.googlegroups.com...
Quote:
Thanks, I want to know; whether total numbers of bases(ACGT) are same
in DNA of all or most of human beings resulting in same chemical
formula of All DNA in all human beings or not? Whether chemical formula
of all DNA in all or most human beings are same but their structural
formula can be different or not?

I don't think I can really answer your question. However, read the sites on
this google search. Understanding the structure of DNA should answer your
question.

http://www.google.com/search?q=dna+%2B+structure&sourceid=mozilla-search&start=0&start=0&ie=utf-8&oe=utf-8&client=firefox-a&rls=org.mozilla:en-US:official
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Jim Chinnis
medicine forum Guru


Joined: 30 Apr 2005
Posts: 1030

PostPosted: Thu May 26, 2005 6:10 pm    Post subject: Re: Question about DNA Reply with quote

"Kumar" <lordshiva5753@rediffmail.com> wrote in part:

Quote:
Thanks, I want to know; whether total numbers of bases(ACGT) are same
in DNA of all or most of human beings resulting in same chemical
formula of All DNA in all human beings or not? Whether chemical formula
of all DNA in all or most human beings are same but their structural
formula can be different or not?

The chemical formula varies from person to person.
--
Jim Chinnis Warrenton, Virginia, USA
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Kumar
medicine forum Guru


Joined: 10 May 2005
Posts: 870

PostPosted: Fri May 27, 2005 3:47 am    Post subject: Re: Question about DNA Reply with quote

"The chemical formula varies from person to person."

Jim, thanks, this awnsers my question.

Whether this variation is due to different numbers of total bases or
due to total numbers of different bases or due to size of DNA?
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Kumar
medicine forum Guru


Joined: 10 May 2005
Posts: 870

PostPosted: Fri May 27, 2005 6:35 am    Post subject: Re: Question about DNA Reply with quote

elgoog, thanks.

Your reply indicates that chenical formulas of DNA of different human
beings will be different. I think it is different due to mutations by
exposures of "environmental factors" which causes changes in sequences
of bases & omissions or the addition of sequences or extra sequences.
Is it correct?

Just one more thought:-

If we would had been in perfect health somewhat alike Adam & Eve, then
if DNA of all of us would have been the same???
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Guest






PostPosted: Fri May 27, 2005 12:53 pm    Post subject: Re: Question about DNA Reply with quote

Kumar wrote:
Quote:
elgoog, thanks.

Your reply indicates that chenical formulas of DNA of different human
beings will be different. I think it is different due to mutations by
exposures of "environmental factors" which causes changes in sequences
of bases & omissions or the addition of sequences or extra sequences.
Is it correct?

Just one more thought:-

If we would had been in perfect health somewhat alike Adam & Eve, then
if DNA of all of us would have been the same???

DNA during replication introduces errors all the time. There are
repair mechanisms that usually, but not always, corrects these errors.
Neither has anything to do at all with environmental insults. They are
simply a part of the natural variation that enables evolution to
happen.

DNA is not anyplace close to a perfect copy from person to person. All
kinds of base pair substitutions, inversions, deletions,
transpositions, etc are in the DNA of all of us. This is simply
natural variation. Most of these things are harmless.

Then there is lots more to the story then even the simple DNA sequence.
For example one copy of some genes are routinely turned off during
development. Which copy is turned off is random. So, two identical
twins who have identical DNA sequences on both copys of the DNA in each
cell show some varitation. Sometimes considerable varitation.

Even changes in the noncoding, so called junk regions, that consume 98%
of the DNA can have dramatic impacts on development. If you want to
learn a little about some of these non-Mendelian aspects do a search on
epigenetics and spend a day or two reading and you will see that there
is lots more to the story then simply the DNA sequence of the genes
themselves. In fact it is looking a lot like this epigenetics stuff
will help us understand a bunch of things that standard Mendelian
genetics can not address.

You also must remember that each gene in a human, on average, produces
about five different proteins. They do this because genes are not
always contiguous. They have what are called introns and exons. And
by activating different combinations different proteins with different
functions in the body are produced. All kinds of subtle chemical
changes in the DNA can impact the ratio of the proteins produced.

Finally, some genes do not even code for proteins. Rather they produce
RNA as the end product. This RNA is used for various regulatory
purposes by the body.

If you really want to get even a fundamental understanding of what DNA
is all about here is a web site that covers the bare beginnings of what
we know today:

http://www.synapses.co.uk/genetics/index.html

This site is written at a very basic level and is only about 15 years
out of date. But if you do not understand what is on this site you can
not even start to ask meaningful questions about what is going on in
the science today.

I suspect you are a pretty bright guy or you would not be asking the
questions you are asking. But even your questions require lots and
lots of typing to even start to answer them in a meaningful fashion.
Like a modest sized book. You need to educate yourself substantially
before you are going to understand the answers I fear. And when you
have that kind of education under your belt you will also realize this
is the wrong forum to be asking these questions. You need to go to a
site that deals with these issues as the main topic.

Or the short answer is that DNA contains all kinds of chemical
variations and such variation is perfectly natural. These chemical
variations in some cases do lead to structural changes as an unintended
and usually inconsequencial result. Changes in base pair sequence due
to environmental insults are quite rare. Although environmental
insults can cause genes to be turned on that should be turned off or
the inverse.
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elgoog
medicine forum Guru


Joined: 28 Apr 2005
Posts: 412

PostPosted: Fri May 27, 2005 6:21 pm    Post subject: Re: Question about DNA Reply with quote

James216440@yahoo.com wrote:
Quote:
Kumar wrote:
elgoog, thanks.

Your reply indicates that chenical formulas of DNA of different human
beings will be different. I think it is different due to mutations by
exposures of "environmental factors" which causes changes in sequences
of bases & omissions or the addition of sequences or extra sequences.
Is it correct?

Just one more thought:-

If we would had been in perfect health somewhat alike Adam & Eve, then
if DNA of all of us would have been the same???

DNA during replication introduces errors all the time. There are
repair mechanisms that usually, but not always, corrects these errors.
Neither has anything to do at all with environmental insults. They are
simply a part of the natural variation that enables evolution to
happen.

DNA is not anyplace close to a perfect copy from person to person. All
kinds of base pair substitutions, inversions, deletions,
transpositions, etc are in the DNA of all of us. This is simply
natural variation. Most of these things are harmless.

Then there is lots more to the story then even the simple DNA sequence.
For example one copy of some genes are routinely turned off during
development. Which copy is turned off is random. So, two identical
twins who have identical DNA sequences on both copys of the DNA in each
cell show some varitation. Sometimes considerable varitation.

Even changes in the noncoding, so called junk regions, that consume 98%
of the DNA can have dramatic impacts on development. If you want to
learn a little about some of these non-Mendelian aspects do a search on
epigenetics and spend a day or two reading and you will see that there
is lots more to the story then simply the DNA sequence of the genes
themselves. In fact it is looking a lot like this epigenetics stuff
will help us understand a bunch of things that standard Mendelian
genetics can not address.

You also must remember that each gene in a human, on average, produces
about five different proteins. They do this because genes are not
always contiguous. They have what are called introns and exons. And
by activating different combinations different proteins with different
functions in the body are produced. All kinds of subtle chemical
changes in the DNA can impact the ratio of the proteins produced.

Finally, some genes do not even code for proteins. Rather they produce
RNA as the end product. This RNA is used for various regulatory
purposes by the body.

If you really want to get even a fundamental understanding of what DNA
is all about here is a web site that covers the bare beginnings of what
we know today:

http://www.synapses.co.uk/genetics/index.html

This site is written at a very basic level and is only about 15 years
out of date. But if you do not understand what is on this site you can
not even start to ask meaningful questions about what is going on in
the science today.

I suspect you are a pretty bright guy or you would not be asking the
questions you are asking. But even your questions require lots and
lots of typing to even start to answer them in a meaningful fashion.
Like a modest sized book. You need to educate yourself substantially
before you are going to understand the answers I fear. And when you
have that kind of education under your belt you will also realize this
is the wrong forum to be asking these questions. You need to go to a
site that deals with these issues as the main topic.

Or the short answer is that DNA contains all kinds of chemical
variations and such variation is perfectly natural. These chemical
variations in some cases do lead to structural changes as an unintended
and usually inconsequencial result. Changes in base pair sequence due
to environmental insults are quite rare. Although environmental
insults can cause genes to be turned on that should be turned off or
the inverse.

James,
Loved your answer. Variations are the essence of DNA. It's built-in.
Variations are what allow us to be different. When the variations are
useful we recognize them as traits. When they are not useful we
categorize them as "errors," but, philosophically I would not consider
them errors so much as an expression of the way DNA replication works.
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Kumar
medicine forum Guru


Joined: 10 May 2005
Posts: 870

PostPosted: Sat May 28, 2005 1:35 am    Post subject: Re: Question about DNA Reply with quote

James, Many thans for detailed reply & advice.

"Changes in base pair sequence due to environmental insults are quite
rare."

"Although environmental insults can cause genes to be turned on that
should be turned off or
the inverse. "

These are quite interesting aspects. Can changes in genes be corrected
within one's lifetime?
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Guest






PostPosted: Sat May 28, 2005 1:48 pm    Post subject: Grossly off topic Question about DNA Reply with quote

Kumar wrote:
Quote:
James, Many thans for detailed reply & advice.

"Changes in base pair sequence due to environmental insults are quite
rare."

"Although environmental insults can cause genes to be turned on that
should be turned off or
the inverse. "

These are quite interesting aspects. Can changes in genes be corrected
within one's lifetime?

At the present state of technology changes cannot be reversed in humans
in general. There are a few exceptions. Such as those who are born
without an immune system. Those people can be cured, in some cases, by
implanting blood stem cells (fetal stem cells would likely work a lot
better) that have the proper genes to develop an immune system. Give
science another hundred or so years and we will likely be able to do
lots more then we can today. Cancers for instance are often caused by
genes being turned off that should be on or the inverse. Perhaps in a
hundred years we will be at the point that we will be able to reset
some of these genes to the proper state and stop the disease. But as a
person who has spent his whole life doing science I doubt very much if
either of us will see much headway in our lives. This is tough work
and we have only just started to get a basic knowledge of what is going
on. Sequencing the human genome was a bare bones start that in itself
will lead to very little of real medical value.

However, there is a bigger misunderstanding that I believe you have
about genetic diversity. Your questions imply that you believe that
there is one best gene for each position. Or one best turned on or
turned off state for each gene. This simply is not true.

Let me give you some of examples of why a diversity of genes is
desired. In areas of high sun intensity dark skin is protective.
Without dark skin you tend to make too much vitamin D and also you are
more susceptable to skin cancers. But in low sun areas light skin is
best. This is because the low sun people need to use as much sun as
possible to manufacture the vitamin D everyone needs.

The second example shows that in some cases having two different genes
is adaptive. In areas where malaria is common people who have one gene
for sickle cell anemia and one normal gene on the other chromosome
survive much better then those with two genes for sickle cell or two
normal genes. Yet in areas that do not suffer from malaria even one
gene for sickle cell is harmful.

The same situation exists with the genes that govern your immune
system. Having different versions, one on each chromosome, allows your
immune system to be more diverse and better able to fight diseases.

This diversity in all living organisms allows them to adapt to the
peculiar environment they happen to live in. There are literally
hundreds of situations known where a diversity can be pointed to as
being adaptive. So thinking that if we could simply "clean up" the
genome by putting only correct genes on both chromosomes at each loci
we get a better human is false. We need the diversity to survive and
prosper. Your Adam and Eve surely had such diversity or the human race
likely would not have survived as they would not have had the genetic
flexability to adapt to new insults. And there will always be new
insults. After all, disease organisms mutate all the time. And a few
of these mutations allow them to get past our immune sytem and kill
many or most of us. But because of genetic diversity there will always
going to be a few survivors who have the ability to survive the disease
and reproduce. Even a disease like AIDs will eventually be licked by
our immune systems when enough people die to allow the genome of the
human race to evolve and provide immunity. And please understand, I am
not in any way advocating we should not treat people who have AIDs.
They are people too and deserve the best medical treatment we can
afford to give them. But historically there have been diseases nearly
as bad as AIDs and the human race adapted by genetically developing the
ability to fight them.

And there are some mutant genes which seem to be of no value at all.
There is no known adaptive benefit to having one copy of the gene for
cystic fibrosis for example. One in roughly twenty of us carries one
gene for this genetic disease. One copy does not seem to harm us
either. It is just a neutral. But give a child two copies and you
have a very ill child with a very short life expectancy. In a hundred
years we may well be able to do the genetic manipulation to at least
give these people one copy of the normal gene in enough lung tissue
that they can live a reasonable life. Maybe even in 10 or 20 years
with a bit of luck. This should be one of the easier genetic diseases
to at least partially correct.

Really, as I said before, you need to do lots of study to get yourself
up to date enough to ask really good questions.
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William Wagner
medicine forum Guru


Joined: 29 Apr 2005
Posts: 809

PostPosted: Sat May 28, 2005 2:10 pm    Post subject: Re: Grossly off topic Question about DNA Reply with quote

In article <1117295329.677489.5050@g14g2000cwa.googlegroups.com>,
James216440@yahoo.com wrote:


Quote:
Really, as I said before, you need to do lots of study to get yourself
up to date enough to ask really good questions.

Chances are there would never be another question asked. Albert said
soon as I say I know I stop thinking about it. Fools like me can elicit
exchange so can other foolish folks. There maybe no bad questions only
foolish answers.

No more post from me for a few days. Remembering families broken.

Bill

--
Garden in shade Zone 5 S Jersey USA
Long -75.0246 Lat 39.637876
Enjoy http://terrafly.fiu.edu/
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elgoog
medicine forum Guru


Joined: 28 Apr 2005
Posts: 412

PostPosted: Sat May 28, 2005 3:36 pm    Post subject: Re: Question about DNA Reply with quote

Kumar wrote:
Quote:
James, Many thans for detailed reply & advice.

"Changes in base pair sequence due to environmental insults are quite
rare."

"Although environmental insults can cause genes to be turned on that
should be turned off or
the inverse. "

These are quite interesting aspects. Can changes in genes be corrected
within one's lifetime?

Not likely. The process is continuous.
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