twins but only has a allergy

[mollykins]

Factor, I wonder if you can even the score which stands one nil to nature vs science teachers. My biology teacher didn't have a clue what the answer was.

There were two (obviously) identical twins in my science class, but only one of them has an allergy to; baked beans, cats and dogs (probably fur in general). But the other doesn't, and neither does anyone else in their family.

If it was genetic, which they both share, they'd both have it. if it was in their environment, which they both share, they'd both have it. But only one does.

so factor, and anyone else who has an answer, how and why has this happened in identical twins who share identical genes and an identical environment (they've never spent a day apart).

[mollykins]

wow, interesting stuff, and I know a big word for when I go on to do more biology.

Could it be that she went to a jamaican (she was born, lived and worked their as a teacher) university, where they don't mention that?

[theprof]

I doubt that very much mollykins. This stuff is fundamental genetics taught all over the world.

I'm a visiting professor at close on a dozen USA universities and I was asked a few years ago to oversee a technically challenging jellyfish venom research project at the University of The West Indies campus at Mona, Jamaica while I was at Brown University in Rhode Island . I jumped at the chance as there was a holiday thrown in!

Anyway, a good understanding of genetics was necessary for the biochemistry project and the research team students, many of whom only had first degrees in biology from Mona, were certainly as knowledgeable in genetics as the students in UK and USA universities. I also sat-in in a couple of genetics lectures beforehand.

I've got little doubt that the genetics modules at the other Jamaican colleges were just as rigorous.

[mollykins]

HHHMMMMM . . . . .

[factor-fiction]

I was flattered that you asked for my thoughts on this mollykins in your original question. Although you say I remind you of an old science teacher you used to have, I'm afraid I'm a mathematician with a lot of experience in law, business and teaching - I have only limited knowledge of other sciences and I'm certainly not in the same league as theprof! I couldn't realy contribute to the discussion on this one.

[Eve]

At the end of the day they come from the same egg, they aren't clones. Even looking at environment, unless they have been kept in a completely controlled identical environment, all kinds of factors could come into play.

We had 9 sets of twins in my year alone at school, most of which from my village so grew up around a lot of them. So so many differences.

[theprof]

Jenna1978, you're mistaken about this. Current thinking asserts that monozygotic twins are indeed effectively clones. In simple terms, all this means that they share the same genotype, which can be regarded as the total genetic complement of a set of genes that an individual possesses containing contributions from both parents.

There is a common misconception in society that clones are absolutely identical in every way but I'm afraid this is not true.

The last half of your first sentence is incorrect : to demonstrate, a pair of monozygotic twins in utero have indeed shared the same "completely controlled identical environment" as you put it, yet they will possess different fingerprints.

Stating that you had 9 sets of twins in your year at school is not very useful as you have not disclosed if the twins were all monozygotic. Were there any dizygotic (fraternal) twins amongst the group? Remember that Boy/Girl twins cannot be monozygotic - the only exceptions are in extremely rare cases of chromosomal abnormalities resulting in conditions such as Turner's syndrome. Fraternal twins show immense differences between each other often to the same extent as brother and sisters born in different years.

Monozygotic twins are invariably of the same gender due to the fact that they form from a single zygote that contains either male (XY) or female (XX) chromosomes.

[Eve]

I have no idea, more my less scientific viewpoint. Mixture of twins though mostly same sex. 4 of my closest friends growing up were made of two sets of twins though I wouldn't know which type there were. I will have to ask them although one is currently in labour so not really the best time haha!

I can only think of one set of boy/girl and they couldn't have looked more different, he was tall, slim and fair and she was short, more rounded and had jet black hair!

My view of clones is a more unsciency one, me thinking of clones is me thinking of something which is completely identical in every way if that makes sense.

[theprof]

It's very unlikely that the number of monozygotic twins in your year at school was any greater than in the general population as a whole, so the majority of them are indeed likely to be fraternal twins.

Your description of the boy/girl twins is typical of fraternal twins - they can be so different sometimes that they look like they have different fathers! People do sometimes find this very odd to accept as they have an ingrained opinion of what two twins should look like.

Your idea of a clone is the same as much of the general population. Most people do indeed seem to think that a clone is absolutely identical in every way so I do understand. I'm afraid that the strict scientific definition is going to take many years to filter down to the public. The news about "cloned" animals entering the food chain over the last few days hasn't helped neither has the ongoing publicity behind "dolly the sheep".

By the way Jenna1978, sorry if I sounded like I was giving you a ticking-off in my last post about your concept of a clone. It wasn't intentional, honest. The grouchy prof should have gone to bed earlier!

[yinyang]

Just reading the answer about peoples idea of what twins should be like. I have twin girls - one has dark wavy hair, the other straight blonde hair and some of thecomments I've had over the years have left me speechless.
'Are they identical?' is a common one, but I've also had' It's not often you see identical twins with different coloured hair, is it?'
Most outstanding one was 'Ah, so they're not really proper twins then.'

[boxtops]

Molly - going back to page 1 - what's a retainer?

[mollykins]

Hhmmm. . . .

People can be so ignorant yin.

The braces that you can take out when you eat etc.

Eddie, hopefully they are all qualified. The maths teacher's third language was english and couldn't pronounce or spell half of the terminology.

[Eve]

Not at all prof, I'm not much of a sciency person, law is my thing and only did science to GCSE :)

Twins are facinating, more later on for me though as, with being around so many from being so young, I guess it didn't seem strange there were so many around. Multiple births too though I know a triplet but no more multiples than that.

Most of them were pretty identical in looks, only one set I struggled to tell apart though I never really got to know them. Off the top of my head, we had 4 sets of two girls, two lots of two boys and one boy girl, the other have escaped my mind completely for now (long day!). 3 non-identical, 4 of those 7 were from my village, 1978/79 must have been a busy year for the local maternity ward :)

[theprof]

EDDIE51, although I was reluctant to point it out, I'm of the same opinion as you. The headteacher of mollykins' school should review how this biology teacher's appointment came about. Most UK universities will have covered this topic by the end of the first academic year, so I'm appalled that this biology teacher was unable to answer the question.

[theprof]

boxtops, a retainer is a dental device made from plastic and/or wires that hold teeth in place either before or after dental braces have been used in a patient undergoing orthodontics. When used after braces are removed, they are usually worn at night to prevent the teeth becoming misaligned again.

[theprof]

yinyang, I do sympathise. I'm sorry to say that the general public are very ignorant about twins in general.