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Original poster

genetics expert, please help??

22 replies

hmb · 23/01/2004 18:21

I know that there are a few genetics experts on Mumsnet, so possibly one of you can help me???

I'm teaching protein synthesis to my year 11s and a question has occured to me that I can't answer. Why does RNA use U instead of T?

Possible answers I have considered. The ribose means that T wouldn't 'fit', T is unstable outside the nuclear membrane or it is 'just one of those things' Any ideas? It is bugging me! I'm probably being a bit dim, as it has been a long week.

Many thanks

OP posts:
tamum · 23/01/2004 18:32

Urrrggg. Um, well, um, it's um....

Nope, haven't a scooby I'm afraid. Brave of me to answer though, eh, I could have just pretended I wasn't on line until after someone else answered

Luckily I know a man who will know, and he'll be home any time now, so I'll report back!

Original poster
hmb · 23/01/2004 18:38

I'm ashamed to admit that in the 4 years that I studied biochemistry this question never occured to me I was making some models to help my year 11s to understand protein synthesis (pipe cleaner, playdough and ping pong balls, who needs an interactive white board??) and I suddenly started to wonder why. I didn't get asked the question today, but I bet I will on Tuesday when I teach them next.

OP posts:
sb34 · 23/01/2004 18:39

Message withdrawn

tamum · 23/01/2004 18:42

No, it has never crossed my mind to wonder. Viruses manage with just RNA after all.

Thanks sb34, but no, we know that bit

Original poster
hmb · 23/01/2004 18:43

Yes, I get that bit. What I want to know is why does RNA use U instead of T? I understand the process of transcription and translation but just wondered why one base was different.

I realise that ran has a different 3-d structure because of the ribose sugar, but couldn't think og a good reason for the switch in bases.

Isn't mumsnet an amazing thing! Thanks for all the help on this oddest of questions

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Original poster
hmb · 23/01/2004 18:44

Make that RNA (or a single point mutation)

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Jimjams · 23/01/2004 18:45

I have a horrible feeling I have read the answer to this at one stage- and can I remember what it is? Not on your nelly. Brain like a sieve you see. Thinking something to do with the evolutionary history of it but cannot remember.

Bet you don't get asked. My student's were never that clever!

Jimjams · 23/01/2004 18:46

but they could probably use apostrophes correctly - actually they couldn't.

tamum · 23/01/2004 18:47

I work on the genetic basis translation factors and it has never even occurred to me

On the plus side, we just found a new breast cancer gene, so that's good!

tamum · 23/01/2004 18:48

Yeah, I thought evolution jimjams, but that's as far as I got...

gingernut · 23/01/2004 18:54

Good grief, you teach this stuff to 11 year olds!

I am very rusty, so I have unearthed a (probably very out of date) copy of Alberts et al, but so far no answer. All I can find is that fact that U and T are structurally very similar, so maybe it is just one of those evolutionary things.

I've never thought about it either.

sb34 · 23/01/2004 19:02

Message withdrawn

tamum · 23/01/2004 19:12

Yes I found that too, but it explains why DNA uses T rather than why RNA uses U, really. Maybe it's a combination of that argument and the evolutionary one; to be simplistic, RNA was first, but is not as good as DNA, which has the advantage for higher organisms of utilising better repair mechanisms.

Gingernut, fortunately I think hmb is talking about year 11 rather than age 11

Original poster
hmb · 23/01/2004 19:13

There is one kids in the class with a sharp quirky mind. I don't think that he will be up to understanding the answer, but it is just his sort of thing to pose the question. Worrying that I never questioned this before.....guess you have to think like a kid sometimes.

Run that last bit past me again.....so the extra energy is 'worth' it, because you keep the integrity of the DNA code intact, but there is no need for that in RNA, is that what you are getting at??

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Original poster
hmb · 23/01/2004 19:15

Yes, year 11, and only for those brave souls who do single science Biology rather than double science GCSE.

Mind you I didn't touch this until A level, so it is tough on them, hence the models made out of plastacine and pipe cleaners! they loved it!

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Original poster
hmb · 23/01/2004 19:16

Sounds plausable tamum.

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Jimjams · 23/01/2004 19:46

oh yes sb34's answer amkes perfect sense. Same idea as urea vs uric acid (which has always stuck in my mind as I was asked it at interview)

Original poster
hmb · 23/01/2004 19:50

Mumsnet is the most amazing resource that I have ever come across. Where else could youpost a question like this and get a reasoned answer withing 40 minutes?

Amazing, and thanks ladies.

If I get asked the question I can now have a good go at answering it, whether they will understand the answer is another thing......

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sb34 · 23/01/2004 19:53

Message withdrawn

gingernut · 23/01/2004 20:07

Oh, thank goodness for that! Can't get used to this year numbering stuff - we started senior school in the upper 3rd and continued (with lower and then upper etc) to upper 6th, except the boys started in lower 4th and had alower, middle and upper 5th. It was all so much simpler in those days .

Original poster
hmb · 23/01/2004 20:11

Oddly, we still have an upper and lower sixth. Another little evolutionary hang over I suppose

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WideWebWitch · 23/01/2004 21:54

Just wanted to say how impressive this all is. It's double dutch to me but blimey!

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