To be open mouthed at Mil's ignorance?

[susannahmoodie]

I'm just so enraged by this...

Mil, a former Psychiatric nurse no less, was telling me about a family friend's new baby. She had seen a picture of said baby and said it was a shame because it looked as it it was "a little bit downs syndrome" and that she always thought friend's wife "wasn't quite right".

I was so open mouthed I didn't reply but I'm going to have to say something aren't I?

For a start, the baby doesn't have ds as afaik and even if it did, Mil's ignorance about their being 'degrees' of downs is a little worrying. It really isn't her place to go round telling people the baby has ds based on a picture of a newborn.

What the hell should I say to her?

Arf at the 'bit Downs' and the 'not quite right mother'. My sister has Downs and we spent what felt like years correcting people who said "Downs baby" "Downs person. It's so obvious really, You wouldn't say "Cerebal Palsy boy." or "Polio man. " Actually, lots of people do.
Someone asked me about a mutual acquaintance whose son has Downs and said "Does he have a touch of Downs himself?"
Also my midwife was most aggrieved that I hadn't told her about my sister at my first booking in appointment. She didn't believe me when I said it wasn't genetic in that way and anyway I didn't care. Came under a lot of pressure to have an amnio, but that's a different thread.

As a matter of interest, what is the mechanism for degrees of Downs Syndrome. Surely a person has an extra chromosome 21 or they dont. Have always wondered when seeing people with different degrees of severity.

I always thought it was something that sometimes ran in families, but not always. I remember Jayne Irving ( tv am presenter) who had two sisters with ds I think. What would be the odds of that being coincidence? Also if it didn't run in some families why would midwives ask about it at booking sessions.

I think your mil wasn't being esp kind, making remarks about the appearance of a baby but I remember my mum's friend giving birth and my mum said to my sad that the baby looked like he had downs. The baby was home a good week before it was diagnosed. The parents hadnt known at all, but my mum was a nurse and just saw something. Sometimes you can just see
that something isn't quite right. There are ways of saying it though. I don't think you should say anything though - she hasn't done this in front of the parents and all that will happen is you will cause a row over something that doesn't affect your life.

I think the degrees thing comes about because sone children have heart problems etc as a result of their ds but other kids are fine. Some people are affected more by it and that csn manifest in severity of learning disabilities as well as physical ones.

montysma1 Surely a person has an extra chromosome 21 or they dont.

Not the case. A person may inherit the extra chromosome from a parent, usually when something has gone wrong with egg or sperm formation. In these situations (and barring freak 'reversal' events), every cell of the person's body will have an extra chromosome.

However, a person may, at some point during development, have an unusual event in just one of the cells of their body which causes that cell and all those derived from it to have the extra chromosome, but which leaves other cells with the normal number. We call this situation 'mosaicism' - the person is a mosaic (patches of difference) for trisomy 21. Depending on the cells (and derivatives) affected by the trisomy, the phenotype (the clinical presentation) may be radically different.

We probably all have at least some cells in our body that contain three copies of chromosome 21.

Louise The vast majority - plus 95% - of cases of Down's syndrome are sporadic i.e. not familial, and caused by a genetic event that doesn't confer any increased risks to siblings.

Louise-there is a rare type of DS called translocation. In this case it may be possible for a mother to not have DS but to be a translocation carrier so that they can pass the condition on to their children and may indeed then have more than one child with DS. It is rare though.

Thanks maid and marrow for the explanations.

I know a little boy with Mosaic Down Syndrome who could be said to look "a little bit" like he has DS. He has the wide forehead but not really any of the other facial features which would perhaps be expected in someone with the syndrome. It's certainly not obvious if you don't know.

I bet mil knows about Downs and was not diagnosing but just being spectacularly rude. The only response in this circumstance is to say "is it really necessary to be so unkind? I don't think I want to hear it thank you." Then say nothing while rude person either tries to justify the unreasonable, apologises or goes on the attack as a form of defence.

Ok thank you. From school biology i thought that that the extra chromosome happened during meiosis so it would be occur at the point when eggs/sperm are made, becoming haploid. Obviously not.

With regards to mosaicism, does that mean that amnio may not always pick up trisomys if the cells can be mixed population or if the event happened later in development than the test was done?

Gah, youthink you understand something!

From school biology i thought that that the extra chromosome happened during meiosis so it would be occur at the point when eggs/sperm are made, becoming haploid. Obviously not.

For most trisomies, the process you describe (uniparental nondisjunction/disomy) is the main cause. Your school hasn't taught you incorrectly, and I teach undergrads the same . I had to get a PhD in developmental genetics stuff to get to grips with the clinical issues of mosaicism!

With regards to mosaicism, does that mean that amnio may not always pick up trisomys if the cells can be mixed population or if the event happened later in development than the test was done?

In genetic mosaics (not just trisomies, but any genetic mutation), it is possible to have skewed test results because:

1. The sample was taken from a tissue that didn't carry the mutation.
2. The sample was taken before the mutation happened.
3. The sample was taken from a tissue that cannot support the mutation, and thus any "mutated" tissue has died away, leaving apparently healthy tissue.

The process for detecting trisomies by amnio/CVS in the UK uses molecular-level detection of chromosome "dose", rather than the more traditional method of taking snapshots of individual cells. The detection of chromosome dose allows hundreds of cells to be analysed all at once, thus improving sensitivity.

Ah I see thank you, was feelng lied to!
I imagined that they just did a straight forward karotype for amnio, but measuring "chromosome dose" makes more sense. Do they look at very conserved markers?

Can I also ask if most trisomys indeed occur during meiosis, why it is that Downs Syndrome is more common in older mothers and put down to elderly eggs. Eggs are already generated in little girls before birth, so the meiosis is not happening in old mums and old eggs. Is that a different pathway again?

Ah I see thank you, was feelng lied to!
I imagined that they just did a straight forward karotype for amnio, but measuring "chromosome dose" makes more sense. Do they look at very conserved markers?

Can I also ask if most trisomys indeed occur during meiosis, why it is that Downs Syndrome is more common in older mothers and put down to elderly eggs. Eggs are already generated in little girls before birth, so the meiosis is not happening in old mums and old eggs. Is that a different pathway again?

I imagined that they just did a straight forward karotype for amnio, but measuring "chromosome dose" makes more sense. Do they look at very conserved markers?

Not anymore in the UK, but believe the US rely primarily on karyotyping still. This will change. Molecular diagnostics are quicker, easier and will be cheaper. The standard kits use a set of reagents that will detect the common trisomies (21 - Down's; 18 - Edward's; 13 - Patau) as well as XY chromosome aneuploidies (incorrect chromosome numbers). They work by PCR, which is way of amplifying then detecting amounts of DNA, usually (as you say) series of markers along each chromosome of interest.

Can I also ask if most trisomys indeed occur during meiosis, why it is that Downs Syndrome is more common in older mothers and put down to elderly eggs. Eggs are already generated in little girls before birth, so the meiosis is not happening in old mums and old eggs. Is that a different pathway again?

You will probably remember that meiosis happens in two sets of divisions, each doing funky divisions of chromosomes? When females are born, we have a full complement of eggs but they are held in a resting state (the prophase of meiosis I) until ovulation, when they complete meiosis I. They don't complete meiosis II until fertilisation. The problem is therefore usually ascribed to older Mums having less-than-optimum cellular machinery in order to complete meiosis at fertilisation, and researchers are trying to find out why that is.

It's also to do with PENETRANCE of the mutation.... This is where a mutation doesn't always show in some environments or shows at a variety of levels - ie a mutation causing a short phentotype where the mutant population on average are shorter than the control group but within the mutant population you get a range of heights ranging from short to regular.

Thank you......!

Done a bit of PCRing in my time but just as a tool, not a geneticist and many moons ago.Should have realised thats what they would do hence the speedy preliminary results.

Thank you......!

Done a bit of PCRing in my time but just as a tool, not a geneticist and many moons ago.Should have realised thats what they would do hence the speedy preliminary results.

Thank you......!

Done a bit of PCRing in my time but just as a tool, not a geneticist and many moons ago.Should have realised thats what they would do hence the speedy preliminary results.

Thank you......!

Done a bit of PCRing in my time but just as a tool, not a geneticist and many moons ago.Should have realised thats what they would do hence the speedy preliminary results.

The extra chromosome may be inherited and the fact there are different classifications or types of down syndrome does not mean someone can be a little bit downs or has a tough of downs. Your mil language is out of order.