I have never heard of pgd - is it a common test? then again there is plenty of things i haven't heard of yet!
yes this weather is driving me insane now. sorry to hear about your changed plans. Are you living with your MIL?
i feel sorry for my little doggy who hasn't walked in a couple of days now due to rain rain rain.
Results 621 to 630 of 1641
02-03-2012 22:09 #621
03-03-2012 08:08 #622
PGD for Lillac
Pre-implantation genetic diagnosis.
Asking if PGD is a common test is like asking if testing your blood sugar is a common test. In the case of blood sugar, if you're diabetic then yes it's common, but if there's no reason to be doing it then it's not. You may enter the PGD world if you (or partner) has a named genetic issue that mustn't be passed on to bubs, or if you've been having repeated problems with your IVF embryo quality or they keep failing to implant.
PGD is sort of self-explanatory. It is diagnosing genetic issues before you choose to give an embryo the opportunity to implant. If you know you have a genetic issue that mustn't be passed on to bubs then you test all the embryos and only transfer those that pass. They take a cell from a day3 (8cell) embryo for testing. If they get the results quickly you can do a fresh transfer on day 5, otherwise you freeze everything until the results come back and do a FET (frozen embryo transfer) on a later cycle.
There are limitations to all types of testing. With genetic testing you only get info on the cells you test, so you have to assume that all the cells you didn't test are the same as the one you chose. In an embryo this might not always be true, you might happen to test the only good cell in a bad embryo, or you might test the only bad cell in a good embryo.
Also, since PGD starts with just 1 cell to test, there's not much DNA to start with, so it might give a false negative result in some tests. If you only look for dodgy genes and it's not there, then that might mean either that all the genes are good, or that that the dodgy bit of DNA got lost somehow before the test was run. A good test will look not only for a dodgy gene, but also for the good version so that you know you've counted the correct number overall.
There are a lot of different tests that fall under the PGD banner.
The first is karyotyping.
karyo = nucleus (part of cell where DNA is kept), with leanings towards implying "chromosomes".
There are a couple of pictures at http://en.wikipedia.org/wiki/Karyotype .
Karyotyping is checking that the number and appearance of the chromosomes is OK. Looking at the first of the wikipedia pics (Karyogram of human male using Giemsa staining) you'll see each chromosome is stripey (zoom in if necessary). Part of the test uses Giemsa dye to stain the chromosomes, and each one has its own characteristic pattern. Based on the pattern and the size/shape of the chromosome they can be arranged into their matching 23 pairs.
tri = 3
soma = body
trisomic = 3 objects
Trisomic conditions, like Downs, will be spotted because there'll be an extra chromosome (#21 for Downs). Adults can also be karyotyped. All you need is a cell with a nucleus, so it's done as a blood test (using white blood cells). Many of the girls (and partners) here will have had the test. It's a first, general look at things.
Because of the banding/stripey patterns you can also spot if two chromosomes have swapped tails with each other (using the colourful method of the last picture might make swaps more obvious). This is a translocation. (trans = across.) If you do the swap neatly and don't lose any DNA then it is a balanced translocation. You still have all the correct info, but it's not in the right place. There's usually no problem with your own health with a balanced translocation, but it makes problems for TTC.
(If it helps, print the either the first or the last (Spectral karyogram of a human female) pic from wikipedia and get a pair of scissors and sticky tape.) Swap over half of one chromosome#1 with half of one chromosome #2 to make a balanced translocation. Everything is still fine in that person, because they've got all the info. But when they go to make eggs or sperm, they only want to pass on 1 of each chromosome. When doing the lucky dip to decide which of each pair to pass on everything will be fine if they happen to grab the chromosomes you didn't swap anything on. One copy of everything will be passed on as per requirements.
If they grab both of the translocated chromosomes then they also pass on all the required DNA, just that half of chromosome#2's DNA is located on #1, and vice versa.
But if they grab the half-and-half #1 and the intact #2 then they'll pass on twice as much DNA for part of #2, and be missing half of the #1 DNA. This is a problem for bubs. In some cases (depending on exactly which genes are involved) it might only be a little problem, but usually it's a big problem.
A little step up from karyotyping is FISH.
Fluorescence in situ hybridisation.
Not sure of your base knowledge of DNA, so forgive me if this is too simple. The four letters used in the DNA alphabet are GATC. These 4 letters refer to the first letter of the name of the chemical structure in the DNA.
DNA is often described as being like a ladder. The ladder comes in a left and right half, and in order to stick it together properly the rungs have to match up, so that a G on one side matches a C on the other, and an A has to match a T. If you try to match a G with an A the sides of the ladder are going to be bulged outwards, and the glue in the middle won't be sticky. If you try to match a C with a T the rungs won't meet in the middle. G+T, or A+C will be the right length, but no glue.
(I remember the pairs visually. G and C are the round letters so they match. A and T are the straight letters so they match.)
If I happen to know that a particular sequence of DNA reads GAATTCA, then I can make my own little sequence that matches it (CTTAAGT, wherever there was a G I wrote a C, etc.) and label my little piece with a fluorescent tag. My piece can now be a useful tool called a "probe". Going back to the karyotyped DNA, I can heat that DNA up which weakens the ladder glue, then throw my probe into the mix and let it all cool down. My little bit should insert itself into the ladder wherever it finds its match (as an irrelevant side effect, the proper long side of the ladder is forced to detour around my probe.) Since my probe fluoresces, then when I look at the chromosomes I should see a couple of bright dots wherever my probe has stuck.
The first wikipedia picture has a green probe that matches one sequence of DNA, and a red probe that matches a different DNA sequence. That picture isn't from a normal cell, so that's all I'm going to say about it.
Now back to PGD. If you know you have a particular gene that's causing a problem then you can make a probe for it and use FISH to see if it's present in your test sample. FISH gives you info on not only what gene is present, but also on how many copies of the gene there are and where it is found.
PCR is a little bit similar to FISH.
Polymerase chain reaction.
PCR is a way of increasing the amount of DNA you have to work on in the lab (using a chain reaction to make a polymer of DNA).
In order to kick off the PCR you need small pieces of DNA like the FISH probes, but without the fluorescent label attached. For PCR, you use 2 probes, and the chain reaction increases the amount of chromosome DNA that's located between where those probes attach.
If you just want to increase the amount of all DNA present then you use probes with random sequences to hopefully include everything in your net. If you're only interested in one gene, then you choose your probes carefully using the known gene DNA sequence so that you only increase the small amount of DNA that you're interested in.
When used diagnostically PCR gives you information on whether the DNA you're looking for is present, but tells you nothing about which chromosome it's on. And when the DNA your looking for is present, PCR doesn't usually say if you have 1 or 2 (or more) copies of it. It's more of a presence/absence (qualitative) test, not a quantitative test. But it's easier to do than FISH. For both PCR and FISH you have to have an idea of what you're looking for before you do the test, because you have to make your probes in advance.
(For completeness, the probes used to kick off PCR are called primers.)
Now there's a "new" test, CGH, which, like karyotyping, can be used when you don't know what problem you're looking for.
Comparative genomic hybridisation.
(I've ripped this explanation from http://www.bubhub.com.au/community/f...r-Women/page48 )
The principle behind CGH is you get:
(a) a sample of "proper" reference DNA and label it a fluorescent colour like green.
(b) a sample of the emby's DNA and label is a different fluorescent colour like red.
Heat an equal amount of both samples up together in the same container so that the rungs of the DNA ladder separate down the middle like a zipper. This leaves the labelled DNA looking for its match when you let it cool down.
Apply the unzipped DNA to a test chip which has unlabelled fragments of DNA already stuck to it so that the fluorescent labelled bits have specific places to zip themselves up to. This forms lots of fluorescent spots on the test chip. A lot of work would have gone into identifying which spots come from which bit of chromosome, and to making sure that each bit of chromosome only had an affinity for one particular spot, before the technique was released for general use.
Use a computer to read the colour of each of the spots. If the colour is yellow then there's an equal amount of DNA (a) and (b) so the emby has the right number of that bit of DNA. (Fluorescent red + fluorescent green = fluorescent yellow)
If there's more green then the emby is missing a bit, so more of the reference sample stuck to the spot.
If there's more red then the emby had extra DNA for that bit, so more of the emby's DNA stuck to that spot.
There's a bit of random wiggle in the colour of the results, but if, say, all the spots for chromosome 4 are red then the emby probably had a trisomy for that. It will also spot unbalanced translocations, and smaller regions of extra/absent DNA where particular spots on the test chip show up too much or too little red or green.
There's a picture of coloured dots at http://www.brookscole.com/chemistry_...GeneChips.html . The brightness of the dot is due to the amount of DNA/label present. The brightness is not as important as colour (red - yellow - green).
Hope that helps.
Last edited by felicita; 03-03-2012 at 08:52.
03-03-2012 09:34 #623
Really felicita....you could write a wonderful easy to understand guide to all thing IVF and it would be a BEST SELLER!!
You really do have a way with words, to make the most complicates things simple to understand.
The Following User Says Thank You to bebehvala For This Useful Post:
03-03-2012 10:25 #624
03-03-2012 10:52 #625
Quick question for Felicita (or EO)...I just saw you post in the LTIVF thread about rose quartz. Can it be any type of RQ jewelry or should it be a necklace, bracelet etc? I am not a very superstitious person but I'm willing to give anything a go this time around. Any info you have, or web links to more info on it would be much appreciated.
03-03-2012 12:51 #626
Bella978 - I don't have any info on it. My sister said "If you believe that sort or cr4p, then rose quartz is supposed to aid fertility, so I got you a cheap necklace because you've already tried everything else," or words to that effect.
And then, as you read in the other thread, I didn't use her necklace but followed the sentiment and got myself a bracelet for Christmas.
Last edited by felicita; 03-03-2012 at 12:55.
The Following User Says Thank You to felicita For This Useful Post:
03-03-2012 15:54 #627
Worth a shot!?!
03-03-2012 17:03 #628
That's pretty. I like it.
05-03-2012 08:33 #629
Sorry no personal I'm on my phone.
I am getting ready for ET at 11:30 this morning
last time I heard of my little embies was on Sat and we still had 5 dividing nicely.
I will come back later this arvo for personals.
05-03-2012 10:00 #630
Alison - so sorry for your BFN. What is DHEA for?
Quartz - how you going??
EO - how long now til your scan? How exciting! Have you tried the wrist bands for nausea? I get motion sickness and always wear them for flights, boat trips (even the ferry - what a loser ). I swear by them.
Lindylou - glad you had a good trip & got your luggage back. I've had mine not arrive after a long haul flight & it's awful. But then it arrived on the next flight so was ok.
catemer - haha, no worries. Unfortunately, just as Felicita mentioned, we need Dr Golovsky - but still don't necessarily have our hopes up of finding any sperm. We wre previously seeing Dr Livingstone at Genea, who referred DH to Dr Lok. He did a TESA and a biopsy, found nothing & only gave us a 5% chance of finding anything with a more invasive op, so we didn't think that was worth it. We dealt with all that at the time & were planning to go to FF and use donor sperm (as much as we liked Mark Livingstone, they don't do anonymous donors there) - we were just waiting for me to recover from the myomectomy I had to remove massive fibroids. Well, it was in the follow up visit with the gyno surgeon after the op that we told him about DH & he suggested we see Dr G. We did and Dr G reckons there's a 50/50 chance he can find some sperm in DH. 50% is pretty good so we're trying that. I don't think there's any rebate from Medicare for the donor sperm.
catfroggy - good luck babe!!! Hope your ET today is a success.
AFM: Well, I think finally this month is a goer! Woo hoo. I had a call from the counseller the other day, who seemed surprised that I hadn't heard from anyone else. But the policy has been changed & all is fine to go ahead, in principle. But she suggested I speak with the Gatekeeper of the Donor List - so I did. She felt confident that she could have us online looking at the donors sometimes this week. It's just that she has to contact the 8 or so couples who are ahead of us first. It made me want to just say, "well don't waste time talking to me then - quick, start calling them!" haha But here's the thing - another weird policy. I can't actually start my cycle unless we have chosen a donor. I explained that my period is due on the 12th & has been a bit erratic so could be early ... which might give us a a very narrow window for choosing a donor. Jeez.
But in other news, I had a really big night on Sat night for a friend's birthday. I didn't realise I had drunk so much, but felt quite ill yesterday all day & into the evening. The birthday was at a Mexican restaurant and I ate too much too - so didn't sleep at all on Sat night as I felt so uncomfortably full. Then felt naseous all day yesterday. I started to wonder if I could possibly be UTD, as we did DTD just before I ovulated. But surely that's impossible!!! Menevit can't be THAT good. Would certainly save us a lot of money & stress ... but then I'd be stressing about having drunk so much on Sat night. I thought it was my last hurrah. Hmm, anyway, extremely unlikely (pretty sure it's impossible actually) but we'll see. I don't feel that queasy today, but tummy still slightly dodgy (maybe it was something in the food), and was sooo tired and had really sore back & legs from too much walking around in high heels, so have stayed home today.
Last edited by peoniesarepretty; 05-03-2012 at 10:03.
By FunKy~Mummy in forum Conception issues & ttcReplies: 274Last Post: 18-06-2015, 21:02
By Bella978 in forum IVFReplies: 950Last Post: 27-05-2013, 11:02
By Sariele in forum IVFReplies: 2Last Post: 19-06-2012, 08:50
Cryosite Family Cord Blood & Tissue BankCryosite has been providing Cord Blood Banking services for over 14 years, and is the trusted choice of Australian ...
LATEST5 ideas for the perfect baby shower giftSurrogacy and why many parents break the lawHow to get your kids to bring home empty lunch boxes
POPULARWhen can I start giving chores to my children?New baby nursery checklist – a guide to newborn essentialsWhat to pack for labour and hospital – a checklist
FORUMS - chatting now ...
Lower back pain! Help!!General Chat
What is the best holiday you have ever had?General Chat
Private health insurance vs extrasPrivate Health Insurance Discussion
Bullying recoveryWorking Hubbers - Employed
April/May TTC group chatConception & Fertility General Chat
Would you help your kids with?General Chat
IVF Babies due Sep/Oct/Nov 2017 #2pregnancy and babies through IVF
IVF/FET April & May chatConception & Fertility General Chat