Seminar 3 2011 Question Page


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Sacred Heart College Student GT 5th May 10p.m.

According to the Embryo Biopsy section of the Focus paper, it is possible to extract a cell from the morula to perform diagnosis without harming the developing embryo. To take this piece of information and apply it elsewhere, is it possible to extract cells from morulas to grow stem cell lines without harming the embryo for stem cell research? A hat tip to our teacher, Mr Cornford, for bringing it up.

 

Bert Stewart, Fertility Associates Live seminar response May 12, 2011

A morula is an odd stage embryo – it is beginning to differentiate. In PDG we take the cells out a day earlier than that at 8 cells. At the 8 cell stage, the cells are totipotent in the morula so I cannot see why you could not potentially do this. In theory you could make stem cells in this way – whether you would want to – from an ethical and cell health perspective would be another question. We know that about 60-70% of the embryos from people we see are aneupliods.

To understand more about stem cells and potency please refer to the National Academy of Sciences Stem Cell Overview


Sonam, Aorere College LiveChat
Why does the number of eggs decrease from birth to menarche (first period) when the eggs are nor being used?

Richard Fisher Fertility Associates Live seminar response May 12, 2011

All the eggs are being used but they are not being used for the purpose they are designed for. There is a constant turn over at every stage from being a fetus until the time you become menopausal there are eggs starting on their phase of development, in the hope that they will hit an endocrine environment, that is hit some hormones that will make them keep developing. So even when you are in a reproductive age in the beginning of the cycle there are 10 – 30 eggs (for a younger woman), but only the one that hits the hormone rich environment will develop and mature, eventually potentially being fertilised, the others will all disintegrate.



Sonam, Aorere College LiveChat
Does age of fatherhood have any effect on fertility? 
 

Answered within the seminar  - Richard Fisher, Fertility Associates

Yes - as a male gets older, the fertility rate decreases and the chance of miscarriage increases. 

 


Aorere College: Sonam (question from LiveChat May 12, 2011)
How does smoking have a negative effact on fertility?


Richard Fisher, Fertility Associates 

 In females smoking reduces the chance of conception per month to 60% of the rate of a non smoker of the same age and health

Some studies of women who smoke have shown:

  • a three times higher incidence of infertility (the decline in fertility is proportional to the number of cigarettes smoked)
  • poorer response to fertility treatment and reduced chance of conception
  • a 50% higher miscarriage rate
  • earlier onset of the menopause
  • each cigarette smoked by a pregnant woman decreases uterine blood flow for up to an hour, resulting in less oxygen for the baby
  • a higher rate of intra-uterine growth retardation, congenital abnormalities and infant death
  • male children of smokers have a higher incidence of learning difficulties and behavioural problems.


Some studies of men who smoke have shown:

  • a reduction in sperm counts and normal structure of sperm
  • a higher risk of impotence
  • increased birth defects and a higher incidence of childhood cancer in their children
  • increased incidence of asthma in their children



Newlands College: Kim (question from LiveChat May 12, 2011)
What time are you most fertile in your menstral cycle?


To achieve conception sperm must be available at the same time as the mature egg is released from the follicle.  Ovulation is the point at which an ovum (or egg) is released from the mature follicle.  This is triggered by a rapid rise in the level of Luteinizing hormone (LH) from the Pituitary gland and occurs at approximately day 14 of a 28 day cycle.  Sperm can survive several days, therefore sexual intercourse in the period 2-3 days prior to ovulation through to about 24 hours after ovulation may result in conception.


Aorere College: Sonam and Wakapitu High School:Tony   (question from LiveChat May 12, 2011)

Do all cells require an X chromosome to function normally and if not, how is development affected by a missing X chromosome  - for example in Turner Syndrome?


Jacquie Bay, LENScience'

Males have one X chromosome and females two. However, only one x-chromosome is active in any cell in the female. One x-chromosome in all non-dividing somatic cells in a female is turned off (randomly) forming a barr body. Therefore in each cell male or female, there is only one copy of the X-chromosome active.  This means that it is possible to have only one copy of the X chromosome, as in Turner Syndrome.



Aorere College: Sonam (question from LiveChat May 12, 2011)
Is the sequence of genes on the x chromosome the same for everyone?

 

The genome is all the hereditary information in an organism, that is the complete set of DNA for an organism which is packed for humans into the 46 chromosomes. Inside each chromosome are genes that code for specific proteins, however the genes only make up about 2% of the total human genome. The rest is the non-coding DNA which plays a role in chromosome structure and regulation of protein synthesis. The Human Genome Project has mapped the human genome, identifying around 25,000 genes. The X-chromosome carries several thousand genes. While each human has the same basic genome, variation within the alleles of each gene create the variation we see from one individual to another. 


Onehunga High School: Anhdao (question from LiveChat May 12, 2011)
Why does having a third chromosome 21 cause problems and how is the severity of down syndrome determined?


Having an extra copy of chromosome 21 effects the expression of genes on that chromsome, It is important not to think of genes as isolated entities, each being responsible for individual components. The products of genes interact with each other in subtle ways. The presence of too much product from a few genes on an extra chromosome may over-suppress or over activate expression of other genes, with a consequent potential cascade effect on other genes.


We do not understand the reasons why there is variation in the phenotype (severity)  of people with Down Syndrome. "Some of the variation in phenotype may be attributed to situations where there is a mosaic pattern of trisomy 21.  This is where there is not an extra chromosome in all the cells of the body, it is just in some of the cells, (those derived from the cell where the extra chromosome arose via non-disjunction). For instance if none of the cells in the brain were affected by the extra chromosome you would not expect to see the learning difficulties. This is part of the reason why we see varying degrees of severity in down syndrome but it is not the only reason. Most people with Down Syndrome have full trisomy 21 in all cells, yet we see major variations in the severity of the expression of the phenotype. The full reason for this level of variability in people who have full trisomy 21 in all cells is not fully understood. 



Waiuku College: Merryn (question from LiveChat May 12, 2011)
How common is Klinefelter's Syndrome?


Klinefelter syndrome affects 1 in 500 to 1,000 males


Hillcrest High School: Nan;  Onehunga High School: Anhdao; Havlock North High School:  Maddy   (question from LiveChat May 12, 2011)

Are people with Down Syndrome normally infertile? If so, why is this the case? if not, if someone with Down Syndrome has children will the children also be affected by Down Syndrome? 

Infertility is a common occurrence for people affected by Down syndrome with nearly 100% of males being infertile and females with Downs experiencing significantly lower conception rates. For males, spermatogenesis is severely affected resulting in the inability to produce sperm capable of fertilisation. Y simple Mendelian Genetics, females have about 50% chance of producing eggs carrying an extra chromosome 21. Women with Down syndrome experience more frequent miscarriages and other complications during pregnancy than non-affected adults, which may be due to complications arising from their own biology or as a result of complications with foetal development.


Hillcrest High School: Chris (question from LiveChat May 12, 2011)
Are there different rates of aneuploidy in twins/triplets compared with singletons?


Yes there are. In New Zealand, as with most areas of the world, approximately one in 1000 children born have Down syndrome. According to The National Down Syndrome Cytogenetic Register in the UK only 2% of Downs children are from multiple births (with only 9 out of 15000 children being a triplet) the other 98% are singletons.  Nevertheless, since the incidence of non-identical twins and the risk of aneploidy both increase with maternal age, the risk of an older mother having a multiple birth in which one child is affected with Down Syndrome does increase.



Marsden Collegiate:  Student S (question from LiveChat May 12, 2011)
I think youre born with all youre eggs youll ever get, is this true?


Yes - that is correct.  The eggs of a female are all present before birth - and even start to reduce in number before birth,


Kelston Boys High School: Kyle (question from LiveChat May 12, 2011)
What's the purpose of meiosis in females if you are born with all the eggs you will ever get, when is meiosis happening?


Bert Stewart, Scientist, Fertility Associates

The first meiosis begins while the woman is still a fetus, with the oocyte chromosomes duplicating. The oocyte then stays at that stage (with a 4n complement) until shortly before the oocyte is ovulated. At that time, the first meiosis is completed and the first separation of chromosomes occurs.


Good question. Meiosis in females does occur differently to meiosis in males; however, it is not entirely true that females are born with all the eggs they will ever have. While cells in the ovaries which will eventually form egg cells begin their differentiation in the fetus, before birth they suspend the process of meiosis at prophase 1, prior to the first cell division. It is not until puberty that one of these cells will divide to form one fertile egg cell and 3 polar bodies. Therefore processes resulting in aneuploidy may occur as early as fetal development, or may occur prior to ovulation.


Aorere College: Sonam (question from LiveChat May 12, 2011)
Women are born with millions of egg cells. What happens to the eggs between birth and menopause to decrease the number of possible egg cells released? Is this linked to fertility rates?

Ovulation is regulated by hormones produced in the ovaries. Although women are born with the potential for many more egg cells to complete meiosis and mature into fertile egg cells than are actually released, the decrease in hormones controlling this process over time is the main cause of reduced fertility and eventual menopause. For many women having trouble conceiving, hormone therapy to regulate irregular or low hormone levels are often the first step to treating fertility problems.


Massey High School: Fardowsa (question from LiveChat May 12, 2011)
What controls mitosis?


Mitosis is a process within the cell cycle.  At each stage of the cell cycle there are checks to ensure that any errors are picked up and if so, the process halted. 
To learn more about control of the cell cycle:




Massey High School: Fardowsa (question from LiveChat May 12, 2011)
Why does the probability of miscarriage increase with age?


Richard Fisher, Fertility Associates Live seminar response May 12, 2011

The risk of miscarriage increases with age because as you get older there is more risk that the embryos will be aneuploid, and the more aneuploid they are the more likely you are to miscarry.



Aorere College: Allysha and Hillcrest High School: Jason (question from LiveChat May 12, 2011)
What causes the increase risk of miscarriage in a woman's pregnancy when she goes through a prenatal diagnostic and tests such as chorionic villus testing? 

Richard Fisher, Fertility Associates

It is certainly about trauma. When the needle is place in the uterus, this makes the uterus more irritable, and you disrupt the normal patterns. If you are going through the amniotic sac (amniocentesis) you are making a small hole in the sac and we think that sometimes fluid leaks through that hole, goes around the outside of the amnion, has a connection with the external environment through the vagina and you get ascending infection. In Chorionic Villus Sampling it is quite a traumatic procedure in which you are having to move a needle up and down inside the placenta and occasionally if you hit a big vessel you will get some bleeding. However all these things are idiosyncratic . It is very difficult to tell at the end of a procedure whether it has gone well or not and so this is the risk of the procedure and if you do it, a minimum level of risk exists.


Richard Fisher, Fertility Associates Live seminar response May 12, 2011 
The issue about chorionic villi sampling (CVS) is that the earlier you look, the more abnormalities you will find. This is because spontaneous miscarriage occurs at every stage of pregnancy, and the earlier in the pregnancy we look, the more likely it is that we are looking at an aneuploid embryo that is likely to spontaneously miscarry. So if you test early you will find more abnormalities. If you wait until amniocentesis, more spontaneous miscarriages will have occurred naturally in the mean time so as a consequence you will find fewer abnormalities. If we go all the way to a full term pregnancy, there will also be spontaneous miscarriages on the way, and there will therefore be fewer aneuploids found at birth. So the graph I showed you in the seminar is showing the rate of aneuploids found at the different satges that testing can occur or at birth – which will decrease due to spontaneous miscarriages during the pregnancy.

'


Massey High School: Fardowsa (question from LiveChat May 12, 2011)
Does the probability of mutation or miscarriage increase if you have a kid at a really young age?

Richard Fisher, Fertility Associates 

Miscarriage rates in general rise as women get older. Beyond 40 the risk if 40-50%. At around 25 it is more like 8-10%. There is some evidence that in very young women (under 15) that the miscarriage rate is increased a little but the differences in real terms are such that it is not noticeable to an individual woman. Miscarriage rates tend to vary across ethnicities and of course increasing age. Older age is the really only significant effect.

Jenny Eaton, ADHB

No, there is no increased risk of chromosome abnormality or single gene mutation in children born to young mothers.


Sacred Heart College:  William (question from LiveChat May 12, 2011)
Can the age which your parent concieve you affect your chance of having children affected by congenital abnormalities?


Richard Fisher, Fertility Associates Live seminar response May 12, 2011

This is a very interesting question and currently the answer is probably not. Although if you look at the incidence of single gene defect, this seems to increase as parental age increases, so it is likely that this may increase the potential of this to affect offspring.


Massey High School: Fardowsa (question from LiveChat May 12, 2011)
Has gene therapy been considered/investigated for fetuses and could it be used at the zygote stage of development?


Bert Stewart - Fertility Associates

The major problem with chromosomes is that they are only visible during a short period of the cell cycle. You would have to see the mistake at that instant in time, and put it right before the chromosomes disappeared from view. Another problem is that in humans they don't line up nicely like in a karyotype photograph (in fact in karyotype slides, they don't like up, but image analysis cuts and pastes them into a nice orderly sequence). To prevent aneuploidy, you would have to carry out the intervention at the first meiosis (which even in IVF situations, happens before eggs are collected), and then again at the second meiosis (which would happen in vitro) then probably again at the first mitotic division. So, with such obstacles in the way, you can appreciate why it is easier to screen for embryos which are OK, rather than repair those which aren't.



Horowhenua College: Julianna and Rotorua Lakes high School: Mimi   (question from LiveChat May 12, 2011)

How does the test determine whether a fetus has a gene mutuion or whether or not its chromosomes are irregular? What is observed following the collection of tissue samples or fluid and how accurate is the information provided by the tests?

Jenny Eaton, ADHB

CVS involves taking a biopsy of the placental tissue (which contains the same genes/chromosomes as the fetus) and Amniocentesis involves taking amniotic fluid that contains fetal skin cells, these cells are then cultured in the laboratory and the chromosomes are analysed, and/or a DNA test (via PCR) is carried out on the tissue for the gene mutation of interest. The tests are highly accurate (99.9%).


Hillcrest High School: Chris (question from LiveChat May 12, 2011)
Is there any upside to having a screening test?

Naturally, the most obvious upside to a screening procedure would be letting parents know that they have been successful in achieving a pregnancy with a developing child who is free from risk of the conditions screened for in the test. For parents who have already given birth to one affected child, diagnostic testing such as PGD provide the opportunity to extend their family with confidence and free from the guilt they may feel as being responsible for causing harm to a child by passing on a rare genetic condition. Screening procedures that occur during pregnancy afford parents the opportunity to make informed choices regarding how they will proceed and may assist them in preparing for the difficulties of caring for children of affected conditions prior to their arrival.




Aorere College: Sonam (question from LiveChat May 12, 2011)
How many eggs are required to be harvested if a woman is interested in IVF?

Richard Fisher, Fertility Associates

We like to obtain between 5 and 15. Less than 5 makes the likelihood of having embryos to select from to replace decrease and consequently the pregnancy rate decreases. More than 15 is associated with a higher incidence of chromosome abnormality in those eggs and so there is little benefit in getting more. In very young women this may not be so pronounced but there has been a worldwide move to lesser stimulation rather than more in the hope of developing a middle sized number of mature normal oocytes rather than a large number of oocytes of variable quality. Sometimes there is little choice about how many eggs we can collect as women with decreased ovarian reserve (and that is mainly older woman) don’t respond in a way to allow more than a few follicles to develop. Not uncommonly women will decide to proceed to IVF with only 3 or 4 follicles as that is as good as they will ever do and although the chance of conception is reduced, it might be their only opportunity with their own eggs.

Bert Stewart, Fertility Associates

Follicle stimulating hormone (FSH) is given to women to try and harvest more than the one egg usually released during a natural cycle. The number of eggs harvested depends on a number of factors, including the womans age. This is done by titrating the FSH dose against age, weight, basal FSH (the level found in the peripheral blood stream at the beginning of a natural cycle…it is a reasonable indication of ovarian reserve).

Too many eggs can lead to problems such as ovarian hyperstimulation syndrome, a potentially life threatening condition, and often when 30+ eggs are collected, many are poor quality.

Of course with some cycles we will only collect one egg despite using large doses of FSH. Louise Brown, the first IVF birth was from a single egg collected in a natural cycle.




Havlock North High School:  Matty and Whakatipu High School: Tony (question from LiveChat May 12, 2011)
What causes the egg/embryo to split to form identical twins?

From a scientific point of view, it is not nown exactly what causes the embryo (blastomere) to divide to form identical twins. Research has suggested that some hormones used to stimulate ovulation have been correlated to the production of multiple births, but it is uncertain whether this has more to do with the mother's sensitivity to the hormones or the effect of the gonadotropins themselves.  From a physical point of view, during development of the blastocyst the zona pellucida surrounding the embryo may herniate and some titipotent cells may 'leak" out.  These cells may become separated from the initial embryo and develop into a twin.  Biochemically, it is likely that the gonadotropins used in fertility treatment cause this zona pellucida to harden unevenly which may lead to an increased chance of rupturing resulting in twins. (The Lancet Volume 329, Issue 8544, 30 May 1987, Pages 1236-1238) 




Aorere College:  Sonam (question from LiveChat May 12, 2011)
What are the chances of producing twins with IVF? 

Richard Fisher, Fertility Associates

One of the good things about IVF is that you can control the incidence of twins by controlling the number of embryos to replace. When IVF started and the chance of any individual embryo implanting was low then it was not uncommon to put 2 or 3 or even 4 embryos back. As implantation rates have improved however, we now normally put only a single embryo back in women less than 38, and only 2 back in women 38 or more. The chance of an embryo dividing into twins after replacement is very small and so the incidence of twins following single embryo transfer is around 1-2%. If 2 embryos are replaced in older women then the risk changes as the age increases and the chances of any individual embryo implanting reduces. The group of people we most commonly see with twins these days are the women in their late 30’s in whom 2 embryos have been replaced and both implant. Unfortunately our methods of embryo selection are not so sophisticated that we can tell which embryo has a very high chance of implantation and which has not. Putting 2 embryos back in older women increases the chance of pregnancy in that transfer cycle but it carries with it the risk of multiples. There was a time in the mid 1990’s to early 2000’s where 2 embryos were commonly replaced across all ages but the incidence of twins reached around 30%, which is of course unacceptable></font>


Horowhenua College: Julianna (question from LiveChat May 12, 2011)
If an embryo has Down Syndrome and splits to form twins does one have the Syndrome or both? Is it possible to be a carrier for Down Syndrome?

If a trisomic zygote or embryo divides to form two embryos, identical twins are the result and both of the twins would be likely to develop Down syndrome. However, if during early cell division the loss of one of the extra chromosomes occurred in even one cell, a mosaic with some cells affected and others being diploid could potentially occur.

According to the National Down Syndrome Cytogenetic Register, Wolfson Institute of Preventive Medicine, St Bartholomew's and the Royal London School of Medicine and Dentistry (website: http://www.mds.qmw.ac.uk/wolfson/ndscr/) identical twins with Down Syndrome are estimated to occur at the rate of 1 or 2 in a million pregnancies and non-identical twins at the rate of 14/15 in a million.

The term carrier normally applies to someone possessing a recessive allele that is not expressed in their phenotype due to the presence of a dominant allele. In the case of Down syndrome the risk of passing on multiple copies of chromosome 21 due to translocation events would also cause us to use the term carrier. For example, someone possessing one normal pair of chromosome 21 and a chromosome 14/21 recombinant chromosome would have the potential to pass multiple copies onto their offspring, even though they may be unaffected.


Sacred Heart College: William (question from LiveChat May 12, 2011)
In the development of identical and fraternal twins, is there ever a possibility of one twin being affected by down syndrome and the other being normal?

Yes! In fact, according to the most recent data from the UK suggest that twins or multiple births occur at a rate of about 2% in the population of 15,000 babies with Down Syndrome. Of 244 twin pairs recorded, 29 pairs show both have Down syndrome with the rest being one affected and the other normal. They report that nine sets of triplets have been born, each with one affected child and in twin pairs where both have Down Syndrome they are not necessarily identical nor do they have to be the same sex.

The National Down Syndrome Cytogenetic Register, Wolfson Institute of Preventive Medicine, St Bartholomew's and the Royal London School of Medicine and Dentistry hypothesizes that in a group of 1000 babies with Down syndrome, some 14 or 15 babies will be a twin or a triplet, with their other twins/triplets unaffected, and 2 or 4 babies will be identical twin pairs, both with Down syndrome.



Havlock North High School:  Matty (question from LiveChat May 12, 2011)
Do twins in nature have a disadvantage compared to singleton offspring?

Richard Fisher, Fertility Associates
Twins is not a normal biological state for humans. They occur sporadically and carry with them some risks. It is not something we ever try to do on purpose with IVF.  The incidence of miscarriage, congenital abnormality, and premature labour with its’ consequences are all increased in twin pregnancy. Fortunately most twin pregnancies lead to normal outcomes but the increased risks of problems are nevertheless significant. The incidence of premature labour is increased by 6-8 times, congenital abnormality in the twins is doubled and the miscarriage rate is also increased.

Bert Stewart, Fertility Associates

In addition to being born early, twins are also commonly born with a lower birthweight.  Increase health risks that are associated with lower birthweight thus impact twins more commonly than singletons. 


Hillcrest High School: Nick (question from LiveChat May 12, 2011)
Does the needle used in IVF damage the egg membrane at all? Are IVF Children affected at all by the process?

Richard Fisher, Fertility Associates

There is a lot of work being done to look at the outcome for IVF children, including at the Liggins Institute. In broad numbers there is no difference in terms of the growth and development of children conceived via IVF. There are some specific things which we have been able to find are different and some of the metabolic parameters which were seen in a cohort of children studies here at the Liggins Institute 4 years ago when they were 8 years old showed that these children were taller and slimmer and did have some metabolic factors that were different from non-IVF children. So there probably are small and subtle differences and those are things that we need to look at. But overwhelmingly the evidence about growth and development is reassuring and we now have IVF conceived children who are having children of their own (not via IVF) who are doing absolutely as you would expect - nothing different from the normal population.



Havlock North High School: Ben and Kyle; Rotorua Lakes High School: Mimi (question from LiveChat May 12, 2011) and Wakapitu High School: Tony (question from LiveChat May 12, 2011)
How does sperm make it into the egg cell normally, given that it requires a massive needle when IVF is used? Do chemicals in sperm assist it penetrating into egg? From the presentation I learned that the sperm tails are cut off prior to injection into the egg cell. What happens to the sperm tails in regular fertilisation?

Bert Stewart, Fertility Associates

The egg is surrounded by cells when it is released at ovulation. The sperm head releases enzymes to help break down the bonds holding these cells together, facilitating its passage to the egg shell surface (called the zona pellucida). The sperm then cuts its way through the shell by changing the way its tail moves (a bit like the movement you would use to scoop frozen icecream out of a tub using a spoon). One inside the shell, the sperm flattens against the egg cell membrane and it is absorbed into it. The entire sperm is absorbed, so the tail is present naturally.


Hillcrest High School:  Ziba (question from LiveChat May 12, 2011) and Kelston Boys High School: Lefata (question from LiveChat May 12, 2011)

Is there any way of knowing anything about the health of the sperm cell selected for IVF? During IVF can you select the sperm that is free from carrying hereditary disease?

Bert Stewart, Fertility Associates Live seminar response May 12, 2011 

When we are doing IVF we cannot choose the sperm. The egg is exposed to a semen sample containing thousands of spemr , from which one will fertilise the egg. With ISCI, we do inject the sperm into the egg so the sperm can be selected. The sperm is the most wonderful cell in the body. It is a specific shape so that it can move through sticky fluid and it has a tail which allows it to get from A to B (by swimming) the sperm head shape is also just big enough to hold the chromosomes. In fact in the sperm head the chromosomes are actually chopped into tiny pieces so that they can be closer packed inside the head of the sperm and can fit into a small place. The shape of the sperm head is also spoon like, allowing it to cut through the zona lucida to get to the egg surface itself. So in normal circumstances, the sperm that is able to get to the fallopian tubes and enter the egg is probably a pretty good sperm. When you look at semen samples there are many sperm that do not look like good quality sperm. They have odd shapes, bent heads, very big or very small heads; all indicating potentially these are abnormal sperms and will not fertilise an egg. When it comes to ICSI, we do not select any sperm that does not look healthy – right shape, size etc. ICSI has been around since 1992, and the data suggests that the outcomes from ICSI tend to be no different to IVF. So the fact that the embryologist is picking the sperm seems to be no better than nature picking the sperm. There have also been many studies done on aneuploidy rates in sperm. To find out whether a sperm is aneuploid, you have to destroy the sperm cell. Whereas we are able to test an egg for aneuploidy without destroying it. We do that by taking the polar body from the egg, and testing that. We assume that if the numbers of chromosomes are correct in the polar body, they will be correct in the rest of the egg. And with the embryos we can biopsy a cell and test it for aneuploidy. However, when studies into aneuploidy rates in sperm are done, around 1/3rd of 1% of a cross section of all sperm (normal shape and abnormal shape) are aneuploid. In the malformed sperm (big pr small heads, bent etc), still only 2- 3% are aneuploid. Whereas in a healthy 25 year old woman 50% of her eggs will be aneuploid. So sperm are not the main contributor to aneuploidy in the embryo.




Havlock North High School:  Emma (question from LiveChat May 12, 2011)
How many years have they been doing the process of removing cells form the embryo for [embryo biopsy]?

Richard Fisher, Fertility Associates 

Robert Winston and Alan Handyside described first successful preimplantation genetic diagnosis in 1989. It took some years before its’ use was more widely dispersed and it was not until 2003 that legislation was passed which allowed the use of PGD in New Zealand.



Newlands College: Lin Ong, 18 May, 2011(9:01pm)
How come people who suffer from down syndrome all look the same?

Down syndrome is caused by the genetic condition resulting from having multiple copies of chromosome 21. The result of additional copies of the genes (particularly on one area of chromosome21) results in the over expression of specific genes on this region compared to people who only have two copies of these genes. The phenotypic features which are common to many people with Down syndrome result from comparable over expression of specific genes found in this region and which are associated with the development of the physical and mental features of those affected with Downs.


Havlock North High School: Kate and Whakatipu High School: Kate (question from LiveChat May 12, 2011) and Newlands College: Lin Ong, 18 May, 2011(9:05pm)
How does removal of a cell (during embryo biopsy) affect the embryo and is it risky? Will embryo culture or embryo transfer affect the egg (or cause any defects)?

Bert Stewart, Fertility Associates We assume that all the cells of an embryo at 8 cell stage are equivalent, ie, removing one does not mean that an important part of the developing embryo will be missing. I think it is fair to say that removing one or two cells at that stage does affect the ability of the embryo to develop further to blastocyst stage. This is normally seen on Day 5 after fertilisation, but with biopsied embryos this may not happen until Day 6.

However, if we wait until the embryo is already a blastocyst, with 100+ cells, then biopsy some of the trophectoderm cells (which would normally produce placental membranes) there is no difference in ongoing developmental potential.