Dory's Biology Questions Thread

[mistermack]

That's true I've heard people talking about anatomy saying that such and such a structure is designed for this purpose

Yes, it's not the kind of thing you learn once, and that's it. I find I have to constantly remind myself that nature is blind and unthinking.
Richard Dawkins made the same point the other day on his program about religious education. He showed that from an early age, the human mind is pre-disposed to giving everything a purpose. Which is why we naturally invent gods.
It's so embedded in our brains, the tendency keeps creeping back in, even with trained scientists, if they don't constantly remind themselves.
.

[Feck]

That's true I've heard people talking about anatomy saying that such and such a structure is designed for this purpose

Yes, it's not the kind of thing you learn once, and that's it. I find I have to constantly remind myself that nature is blind and unthinking.
Richard Dawkins made the same point the other day on his program about religious education. He showed that from an early age, the human mind is pre-disposed to giving everything a purpose. Which is why we naturally invent gods.
It's so embedded in our brains, the tendency keeps creeping back in, even with trained scientists, if they don't constantly remind themselves.
.

My school biology teacher used to write " BY WHO ?" in a big thick red marker pen on your work if you did

I was horrified to learn that at least one University anatomy school in this country actually teach things that way !

[Dory]

Q: How to detect RNA if there are radioactive bands in the probe?


This question is rather confusing to me. DNA and RNA probes have always preplexed me. Perhaps someone (ahem...GFL) can help shed some light on that issue and probes in generl?

[GenesForLife]

Q: How to detect RNA if there are radioactive bands in the probe?


This question is rather confusing to me. DNA and RNA probes have always preplexed me. Perhaps someone (ahem...GFL) can help shed some light on that issue and probes in generl?

The idea is that DNA and RNA is separated before being subjected to probe hybridization, once the nature of the nucleic acid you are studying is known, double stranded nucleic acids are denatured, while RNA isn't, after separation by electrophoresis, a sequence specific oligomer is added to the sample and allowed to hybridize, if there is a complementary sequence the probe will bind to it, and the unbound probe can be washed off, when subjected to autoradiography, the bound probe, being radioactive, will mark the location of the complementary sequence it has bound to.

I want you to have a look at this...

[Dory]

Oh, and the point in all that I presume is to detect the position of the probe right? And it's all thanks to a autoradiograph really that it works.

[GenesForLife]

Oh, and the point in all that I presume is to detect the position of the probe right? And it's all thanks to a autoradiograph really that it works.

Yup, probe binds to sequence, therefore probe location = sequence location.

[GenesForLife]

There of course is another technique that uses probes, but fluorescent ones, called FISH (Fluorescent In-Situ Hybridization) where probes are used to locate sequences on chromosomes.





Cute, innit?

[Dory]

There of course is another technique that uses probes, but fluorescent ones, called FISH (Fluorescent In-Situ Hybridization) where probes are used to locate sequences on chromosomes.





Cute, innit?

Oh this is so cool

[Dory]

How fast does it take to translate an average mRNA strand to a protein? miliseconds? seconds? minutes? hours?

[GenesForLife]

How fast does it take to translate an average mRNA strand to a protein? miliseconds? seconds? minutes? hours?

Depends on the length of the strand and the number of ribosomes working on the chain (especially in bacteria, where mRNA is polycistronic, several genes are translated at once)

Answers.com has this to say...

The bacterium E.coli can add an amino acid in only 0.05 second. That means that synthesizing a protein of 300 amino acids takes only 15 seconds.

But is this the gold standard for all organisms? Doubtful, so if you want to answer that question, you may have to carry out studies of protein turnover...

[Dory]

Hmm, I expected it to determine on many factors, though I did wonder what's the approximate distribution. 15 seconds for 300? Cool. Not as fast as I thought these babies normally go

[GenesForLife]

Hmm, I expected it to determine on many factors, though I did wonder what's the approximate distribution. 15 seconds for 300? Cool. Not as fast as I thought these babies normally go

The reaction to add each amino acid is a multi-step one, Dory... you need ratcheting, incorporation of aminoacyl tRNA, and the formation of peptidyl transferase, while involving GTP cleavage and the involvement of Elongation Factors Tu and G, of course, you also need to eject the empty uncharged tRNA in the E site of the ribosome.

[Dory]

Hmm, I expected it to determine on many factors, though I did wonder what's the approximate distribution. 15 seconds for 300? Cool. Not as fast as I thought these babies normally go

The reaction to add each amino acid is a multi-step one, Dory... you need ratcheting, incorporation of aminoacyl tRNA, and the formation of peptidyl transferase, while involving GTP cleavage and the involvement of Elongation Factors Tu and G, of course, you also need to eject the empty uncharged tRNA in the E site of the ribosome.

And does the empty uncharged tRNA go to the cytoplasm to get hooked up with its correlating amino acid?

[Dory]

Are mitochondria immobile or do they move within the cell?

[GenesForLife]

Hmm, I expected it to determine on many factors, though I did wonder what's the approximate distribution. 15 seconds for 300? Cool. Not as fast as I thought these babies normally go

The reaction to add each amino acid is a multi-step one, Dory... you need ratcheting, incorporation of aminoacyl tRNA, and the formation of peptidyl transferase, while involving GTP cleavage and the involvement of Elongation Factors Tu and G, of course, you also need to eject the empty uncharged tRNA in the E site of the ribosome.

And does the empty uncharged tRNA go to the cytoplasm to get hooked up with its correlating amino acid?

Until it is degraded, it is free to be recycled...

I have this abstract of a study on rats...

The tRNA fraction, extracted from very high speed supernatant fluid, from livers of rats injected with 3H-orotic acid, attained maximum specific activity after a little over 24 hr and, thereafter, decayed with an apparent half life of 5 days. This behaviour of tRNA was indistinguishable from that of liver rRNA and the acid soluble pool. Chromatography of tRNA, doubly labelled during a period of short synthesis and of prolonged decay, on a BD cellulose column, indicated that individual tRNA species turn over at a constant rate with respect to one another.

http://www.sciencedirect.com/science?_o ... 5bb709b527

AFAIK, there is no "locking" or "blocking step" involved in translation, the logical answer would be that reuse until degradation has an evolutionary advantage and this could be expected (think reduced transcription costs in not having to make said tRNA afresh) , mRNA, however, I suspect, has a very short half-life, and is degraded quickly after translation.