[neilep (OP)]

Well, I've done the bacteria/cell thing (counted every one myself) so now I thought I'd chuck a few DNA facts at you:

In almost every cell you have about 2 metres of DNA

Each length of DNA comprises some 3.2 billion letters of coding, enought to provide 10 to the power of 3,480,000,000 possible combinations......that's a one followed by more than three billion zeroes (nearly the amount of my income in £'s)[]

YOU are beholding ten thousand trillion cells and almost every one holds about 2 metres DNA...enough that if it were all woven together it would stretch to the moon and back, not once, not twice but again and again.According to one calculation you may have as much as 20 million kilometers of DNA bundles up inside you....which is nice !

And that's waht I have to say about that.



'Men are the same as women...just inside out !'

[NutriDude]

OK, so whole-body DNA (about 0.5g, it is said), when stretched out and laid end-to-end reaches a pretty impressive length, but it's only impressive because no one usually bothers with these sorts of calculations. If you want a far more impressive figure than that for DNA, calculate the end-to-end length of a human body's-worth of uncoiled protein! We have kilos of the stuff. Or, for that matter, how about lining up 1 measuring cup's-worth of sucrose molecules and measuring that length? Or the water molecules from one typical urination? Any of these would make the DNA value seem puny.

ND

[neilep (OP)]

Hi Nutridude, I was just mentining DNA that's all about some facts that I came across, it was never with the intention to belittle the facts of uncoiled protein. Just because there are more impressive facts available doesn't mean the the DNA facts should have not been cited eh ? Please feel free to furnish us with your more impressive facts.

Welcome to the site.

'Men are the same as women...just inside out !'

[MayoFlyFarmer]

quote:Originally posted by NutriDude

OK, so whole-body DNA (about 0.5g, it is said), when stretched out and laid end-to-end reaches a pretty impressive length, but it's only impressive because no one usually bothers with these sorts of calculations. If you want a far more impressive figure than that for DNA, calculate the end-to-end length of a human body's-worth of uncoiled protein! We have kilos of the stuff. Or, for that matter, how about lining up 1 measuring cup's-worth of sucrose molecules and measuring that length? Or the water molecules from one typical urination? Any of these would make the DNA value seem puny.

ND

yeah, but who really cares about a cp of sucrose...   DNA is way cooler because of how many different things it can code for and how much of it we don't even understand.  thats why its impressive how much you have.

That's no moon.... its a GRAPEFRUIT!!!!

[neilep (OP)]

quote:Originally posted by MayoFlyFarmer

quote:Originally posted by NutriDude

OK, so whole-body DNA (about 0.5g, it is said), when stretched out and laid end-to-end reaches a pretty impressive length, but it's only impressive because no one usually bothers with these sorts of calculations. If you want a far more impressive figure than that for DNA, calculate the end-to-end length of a human body's-worth of uncoiled protein! We have kilos of the stuff. Or, for that matter, how about lining up 1 measuring cup's-worth of sucrose molecules and measuring that length? Or the water molecules from one typical urination? Any of these would make the DNA value seem puny.

ND

yeah, but who really cares about a cp of sucrose...   DNA is way cooler because of how many different things it can code for and how much of it we don't even understand.  thats why its impressive how much you have.

That's no moon.... its a GRAPEFRUIT!!!!

Justy..*sigh*...my hero !!![] (in a blokey back slapping kinda way of course !!)

'Men are the same as women...just inside out !'

[kristin]

well, its my first itsy, bitsy post here[:I] just found this site today.

just wondering if any of you know of any good sites, articles related to genetic fingerprinting[?]

i have to write a 1000 word essay on it, by the end of the week, and im a bit tired of searching bloody google. [xx(]

[chris]

Have you had a look at :

http://www.thenakedscientists.com/HTML/articles/article/dalyacolumn8.htm

It's one we did recently and covers the process, pretty much.

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[kristin]

heya[]
yeah, i know, that's how i found this page. i'm looking more for ethics, social stuff on it now. my essay is 'the arguments for and against developing a genetic fingerprint profile for everyone in society'.. hmm, now there's a mouthfull...[:p]

[befi]

quote:Originally posted by chris

Have you had a look at :

newbielink:http://www.thenakedscientists.com/HTML/articles/article/dalyacolumn8.htm [nonactive]

It's one we did recently and covers the process, pretty much.

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[paul.fr]

heya[]
yeah, i know, that's how i found this page. i'm looking more for ethics, social stuff on it now. my essay is 'the arguments for and against developing a genetic fingerprint profile for everyone in society'.. hmm, now there's a mouthfull...[:p]

Ok, this may be an old topic but it is pretty relivant to all of us. here is why.

The Uk has the largest, or one of, DNA databeses. If you have been cautioned, arrested , had a paternity test or just interviewed it is most likely you are in the database. all well and good you may think, this is bound to help catch those pesky criminals now that we have such a large sample base.

Not so, the forensic science service now hae a system called low copy number dna (lcn). this increases  your chance of being a suspect and is so unreliable that even the FBI do not use the system.

just watch where you leave your dna, Pere falconio was convicted using this method of dna testing and is now appealing on grounds that the test is floored.

Paul

[Mjhavok]

DNA ---->RNA ------>Protein

RNA has intermediate role

DNA is the hereditary material in most living organisms (RNA in a few)

Nucleic Acids

DNA (Deoxyribonucleic acid)

Acts as template to reproduce an exact copy of itself.
Is used to pass on information to its descendants
Encases specific information which is used to direct protein synthesis.

RNA (Ribonucleic acid)

Constructed as a complimentary copy from DNA
Three types exist: ribosomal (rRNA), transfer (tRNA) and messenger (mRNA).
RNA carries information which directs protein synthesis.

Central Dogma

Three components: DNA, RNA and Protein.

Information flow
DNA codes for RNA (transcription)
RNA codes for protein (translation)
DNA does 'not' code directly for protein but uses the intermediary RNA.



1869 - Friedrich Miescher 

Removed material from nuclei of puss cells: “NUCLEIN”
Rich in phosphorus, no sulphur.
Concluded very different from protein.

1928: Frederick Griffith

Trying to develop a vaccine against Streptococcus pneumoniae
Isolated two strains
S Strain. Shiny colonies (polysaccharide capsule), virulent (killed mice)
R Strain: rough colonies (no capsule), non-virulent (didn't kill mince)

Was the capsule causing the virulence?
Injected heat killed S Strain into mice, they did not die
Injected a mixture of heat killed S Strain and Live R Strain (neither individually killed mice)
      -Many mice died
      -Blood Samples contained live S Strain.



Griffins conclusions
      -Substance used in capsule synthesis must have passed from the dead S Strain to the live R Strain.
      -Transformed the R Strain into S Strain
      -Information passed onto descendants.
      -Change in phenotype (physical appearance) must be due to change in genotype (genetic material).
      -Griffin did not know transforming substance.



1944 – Avery and co-workers

Proposed DNA as “transforming substance”
DNA from dead S strain caused R strain to be transformed.
Transformation not blocked by enzymes which degrade protein or RNA.
Transformation blocked by enzyme which degrades DNA.
Chemical and Physical properties of transforming substance DNA

1952 – Hershey and Chase Experiment

Used bacteriophages: viruses which attack bacteria
Composed of DNA/RNA surrounded by a protein coat.
Attach to bacterial surface and infect by injecting hereditary material into bacteria
Produce thousands of new phage, released which bacteria lyse.



Experimental evidence

DNA is the hereditary material.

DNA is the definitive hereditary material in eukaryotes, bacteria and most viruses.
Griffith's experiments: hereditary material passed from dead bacterial cells to living ones, transforming them.
Avery's experiments: Conclusive evidence for DNA as the hereditary material.
Hershey and Chase experiments: The hereditary material was DNA and not protein.

The Central Dogma and RNA Viruses
   
Do RNA containing viruses conform to the central dogma?

1957: Fraenkel-Conrat performed virus reconstitution experiments using TMV and HRV.
Conclusion: The RNA conferred the hereditary properties of the virus, not the protein.

DNA virus infects cell, inserts DNA into host cell chromosome.
What of RNA viruses (retroviruses)?
Use reverse transcriptase and RNA to make DNA, insert this into host cell chromosome.
Transcribe this into RNA then protein.
DNA is the hereditary material for all cellular organisms and most viruses.
Retroviruses use RNA as their hereditary material to construct DNA.

They do conform to the central dogma

RNA----->DNA----->RNA----->PROTEIN


DNA Structure

Chemical Analysis of DNA

1920s – Levene demonstrated roughly equal quantities of:

Phosphate groups (PO4)
5 Carbon sugars
N2 containing bases
     -Purines (Adenine(A) and Guanine(G))
     -Pyrimidines (Thymine(T), Cytosine(C) and in RNA, Uracil(U).
     -Proposed repeating units (nucleotides)
     -String together in a long chain.



Nucleotides linked via 5' phosphate group and 3' hydroxyl(dehydration) by a phosphate bond (P-O-C)
Many nucleotides linked together, but still have free 5' PO4 and 3' OH group each end of the molecules (directional molecules)
Base sequence expressed in the 5' to 3' direction.
Almost equal amounts of A, T, G and C, led to hypothesis that DNA was a polymer of 4 repeating nucleotides e.g.. ATGC-ATGC-ATGC-- (WRONG!!)


Chargaff's Rules

Later analysis demonstrated that proportions of nucleotides varied depending on the source of DNA.
The amount of adenine present in DNA always equals the amount of thymine and the amount of guanine always equals the amount of cytosine i.e. A=T and G=C.
There are always equal amounts of purines (A and G) and pyrimidines (C and T).

TB bacteria composition    A=15.1%   T=14.6%
            G=34.9%   C=35.41%

Herring composition      A=27.8%   T=27.4
            G=22.2%   C=22.6%

3D structure of DNA

Franklin's X-ray studies: A helix, diameter about 2nm; complete helical turn of 3.4nm
Watson and crick: Double helix, bases protruding inwards forming complementary base pairs.
Hydrogen bonding between nitrogenous bases stabilises the double helix.
Adenine pairs with thymine (2H bonds)
Guanine pairs with cytosine (3H bonds)
Heat separates DNA very easily



Two strands are anti-parallel i.e. One chain runs 3' to 5' and the other runs 5' to 3'
AT and GC base pairs can occur in any order along the DNA molecule, giving rise to immense variability e.g. the DNA molecule, giving rise to immense variability e.g 46 human chromosomes contain approximately 3 billion base pairs of which approximately 140 million are coding sequences giving rise to 4140 million possible nucleotide sequences.
Resembles a twisted ladder (hydrogen bonded base pairs = the rings, sugar-phosphate backbone = the sides)



DNA Structure Summary

DNA series of nucleotides joined by phosphodiester bonds, directional molecules.
Chargaff's rules : A=T, G=C, A+G = C+T
DNA is a double helix held together by hydrogen bonding between base pairs (twisted ladder).

[Mjhavok]

That post took me like 20 minutes. I want praise lol.

[neilep (OP)]

Mate that is an extraordinarily excellent post !!

[Mjhavok]

ChEErS!

[paul.fr]

That post took me like 20 minutes. I want praise lol.

and praise of the highest order too.

[another_someone]

Ok, this may be an old topic but it is pretty relivant to all of us. here is why.

The Uk has the largest, or one of, DNA databeses.

I vaguely recollect some time ago that Iceland had decided to collect its entire population DNA data (but that was only for medical research, and so was anonymised).

[another_someone]

DNA ---->RNA ------>Protein

RNA has intermediate role

DNA is the hereditary material in most living organisms (RNA in a few)

Except, is there not some evidence that some epigenetic (neuvo Lamarkian) inheritance does exist?

[Mjhavok]

It doesn't affect the central dogma as far as I know.

[another_someone]

It doesn't affect the central dogma as far as I know.

Not sure what you mean by that.  If you mean that DNA remains the dominant means of inheritence, then probably yes; but would it not mean that DNA is no longer regarded as the only means of inheritance?

[WylieE]

Nice Post and Summary, that must have taken a lot of work!

Except, is there not some evidence that some epigenetic (neuvo Lamarkian) inheritance does exist?

Yes, there are definitely some epigenetic forms of inheritance and these are generally considered exceptions to the central dogma.

Some more obvious exceptions . . Reverse Transcription- where an RNA can be a template for DNA.

Prions might be considered an exception too- proteins making heritable proteins.

Of course this is my favorite version of the central dogma:  [ Invalid Attachment ]

Sorry about the lousy drawing