Dory's Biology Questions Thread

[Feck]

The problem with triploid cells would be mitosis, anaphase and metaphase would be all messed up .

[GenesForLife]

The problem with triploid cells would be mitosis, anaphase and metaphase would be all messed up .

<nods>

[Dory]

I'm guessing meiotic failure because pairing of homologous chromosomes doesn't take place.

This question is confusing me on many levels. I saw it on Yahoo Answers. I didn't even know that there are triploid zygotes can exist. So if they exist, apparently they're sterile...because of what meiotic failure? Don't you mean meiosis failure?

At the risk of sounding VERY pompous, there is an important thing to learn in this. "Why are they sterile" is very much the wrong question.
We should be AMAZED if they were fertile.
It's very tempting to picture life as having a purpose. That's how our human minds work. When we are little, we think water is for us to drink, or have a bath. Air is so we can breathe. etc. etc.

But the truth is there is hardly any purpose in anything.
We imagine that creatures exist so that they can reproduce. That's just as wrong. They exist because their ancestors DID reproduce.

Imagine life as a row of dominoes standing on their ends. You knock the first one over, they fall in turn all the way to the end. If the last one gets knocked over, one or two new rows automatically pop up, and it all starts again.
When we humans set dominoes up, we have a purpose, and can fix it if one domino is slightly askew.

Nature has no purpose at all. If one domino misses the next, the end domino never falls, and that line of dominos becomes extinct.
That's your triploid zygote. It never had a purpose. It rarely knocks over the last domino, if even one of them is slightly offcentre.
.

For the record though I was the quoting the question from another source, it just made me wonder.

[mistermack]

For the record though I was the quoting the question from another source, it just made me wonder.

Yeh, that's why I wrote "at the risk of sounding pompous".
But it's such an easy thing to fall back into, assuming purpose, that you very often come across very qualified people doing it. Especially in evolution, more so than the mechanics of biology. They say, why don't animals evolve this way, or that? which can lead to all sorts of false assumptions.
.

[Feck]

For the record though I was the quoting the question from another source, it just made me wonder.

Yeh, that's why I wrote "at the risk of sounding pompous".
But it's such an easy thing to fall back into, assuming purpose, that you very often come across very qualified people doing it. Especially in evolution, more so than the mechanics of biology. They say, why don't animals evolve this way, or that? which can lead to all sorts of false assumptions.
.

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

[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...