A quick Question...

[jayson]

I have a quick question (it was on the test)

There is a nucleic acid consisting of

Adenine = 20%
Thymine = 25%
Guanine = 35%
Cytosine = 20%

Describe the nucleic acid, and its structure.



Basically,okay you know how in a DNA Adenine and Thymine quantities are suppose to be the same, along with Guanine and Cytosine. But here in this nucleic acid, they are all different. SO what kind of nucleic acid is it ?

I wrote "It is DNA, but some of the nucletides are missing and there could be severe mutation."

But some people in my class told me that they wrote RNA, which I did think of as the answer but it wouldn't make sense since RNA has Uracil. I was wondering how would you guys identify this "nucleic acid"

[sdekivit]

i don't understand this question :s

[mith]

maybe the dna strand has "sticky ends" ends which do not have complements.

[Jennifer]

The N.A. is probably just single stranded.

[Terry K.]

I'll bet it's a bacteria/virus of some sort because most of the time either of these two don't have equal percentages of complementing base pairs.

[canalon]

I'll bet it's a bacteria/virus of some sort because most of the time either of these two don't have equal percentages of complementing base pairs.

DNA virus, and bacteria have regular double stranded DNA so I don't really understand your comment.

RNA was also what first came to my mind, but jayson argument against it seem quite right to me. So single stranded DNA, but with that clues I don't really see what we can deduce anymore about structure (probably some secondary structure to stabilize this but...)

[jayson]

So its a single stranded DNA ?

Man that just pisses me off. Lost four good marks right there. When I lose makes in BIO it hurts deep within. I know this stuff inside out, but always these small things mess me over.

What are the possible advantages of SS DNA over double helix that an organism would choose to have SS DNA ?

[canalon]

Beats me, It's the only things that fits the 2 basic facts:
- DNA because of thymine, not Uracil
- Single stranded because otherwise there would be equal amount of A+T and G+C

But except if you really want to talk about the very rare case of non classical appariements between base I do not have the slightest idea what else it can be. But be sure to tell us the answer when you know it, I am interested. And I may be wrong.

[jayson]

Seems like the answer was single stranded Dna.

Where do you find ssDNA ? What are the possible advantages of having ssDNA as oppose to double helix, anyone know. Thanks in advance.

[canalon]

Ooops I was wrong, ssDNA viruses do exist (But I am really not interested in viruses, you need to understand their host to understand how they work, and then it's complicated for me, I prefer bacteria:wink:). So it could be the source of your molecule. As for the advantage... no idea. More compact? result from their rolling circle replication? anything else? Maybe victor our virus specialist could help.

[krusaider]

ssDNA viruses exist ofcourse. eg, phage M13 used as a cloning vector. DNA is cyclic and always of same strand i.e. molecules from different virions do not form double helix on annealing together .Direction of the strand in all virions is same 5'-3' or they other way. Advantage :me thinks to get packaged in the small phage head.

[MrMistery]

yeap, there are a lot of single stranded DNA viruses. And i agree that this was the answer the teacher probably wanted. There are 2 kinds of ssDNA viruses:
-when DNA is linear(example: phi M13)
-when DNA is circular(example: phi X174-host E.coli*for patrick*)

I don't know what the advantage of having such a type of genetic material is, maybe it is "cheaper" in energy to make or easier to infect, but a very important thing for us scientists is that they show the evolution of DNA from RNA, by having this "primitive" kind of DNA