Guest guest Posted September 19, 2003 Report Share Posted September 19, 2003 I " m not sure. But i was thinking the same thing you are from reading back in the archives. My friend Audrey's twins will be undergoing genetic testing and they will be testing them for this. Her twins are identical though and only one seems to show symptoms simialar to those of RSS kids. I can't wait to see the replies you get. > Hi, > I am just curious. It sure seems that a large number of RSS kids are > fraternal twins. Does being a twin increase the odds of a particular > child being RSS. > Conny Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 19, 2003 Report Share Posted September 19, 2003 At 08:15 PM 9/19/2003 +0000, you wrote: >I " m not sure. But i was thinking the same thing you are from reading >back in the archives. My friend Audrey's twins will be undergoing >genetic testing and they will be testing them for this. Her twins are >identical though and only one seems to show symptoms simialar to >those of RSS kids. That seems to indicate that RSS may not always be truly genetic after all? Aren't identical twins genetically identical? Or maybe there are differences even in 'identical' twins... Inga I can't wait to see the replies you get. > > > > > >> Hi, >> I am just curious. It sure seems that a large number of RSS kids >are >> fraternal twins. Does being a twin increase the odds of a >particular >> child being RSS. >> Conny > > > > > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 19, 2003 Report Share Posted September 19, 2003 Actually, we looked into fertility drugs/in vitro increasing the odds of RSS not that long ago here. We did a poll on how many of us used fertility drugs. As it was not really a scientific poll, we couldn't come to any conclusions. However, many multiples are due to fertility drugs etc. If you look in the archives you may be able to find all the posts. Judith, Steve, (RSS) and (non RSS) 3 1/2 year old twins Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 19, 2003 Report Share Posted September 19, 2003 Actually, we looked into fertility drugs/in vitro increasing the odds of RSS not that long ago here. We did a poll on how many of us used fertility drugs. As it was not really a scientific poll, we couldn't come to any conclusions. However, many multiples are due to fertility drugs etc. If you look in the archives you may be able to find all the posts. Judith, Steve, (RSS) and (non RSS) 3 1/2 year old twins Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 19, 2003 Report Share Posted September 19, 2003 Yeah identicals are genetically the same. Blood type and everything. HOwever there are many types of identical twins. THere are even gentically idential twins that are boy/girl although the girls suffer from 's Sundrome(I'm pretty sure that is what is is) when this happens. > >> Hi, > >> I am just curious. It sure seems that a large number of RSS kids > >are > >> fraternal twins. Does being a twin increase the odds of a > >particular > >> child being RSS. > >> Conny > > > > > > > > > > > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 20, 2003 Report Share Posted September 20, 2003 I think there are one or two other cases of identical twins, one having RSS the other not. I think with twins, often one is smaller than the other (sometimes much smaller) since we are still not really sure what causes RSS - possibly sometimes it's related to early intrauterine growth restriction, but nobody really knows, it's just a theory.... ((HUGS)) Steph > > Hi, > > I am just curious. It sure seems that a large number of RSS kids > are > > fraternal twins. Does being a twin increase the odds of a > particular > > child being RSS. > > Conny Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 20, 2003 Report Share Posted September 20, 2003 I thought being a boy or girl is in the genetic code, so that if one is different they have to be genetically different - unless there is only a subset of the genes that they compare or something? Inga At 08:35 PM 9/19/2003 +0000, you wrote: >Yeah identicals are genetically the same. Blood type and everything. >HOwever there are many types of identical twins. THere are even >gentically idential twins that are boy/girl although the girls suffer >from 's Sundrome(I'm pretty sure that is what is is) when this >happens. > > >> >> Hi, >> >> I am just curious. It sure seems that a large number of RSS >kids >> >are >> >> fraternal twins. Does being a twin increase the odds of a >> >particular >> >> child being RSS. >> >> Conny >> > >> > >> > >> > >> > >> > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 20, 2003 Report Share Posted September 20, 2003 I thought being a boy or girl is in the genetic code, so that if one is different they have to be genetically different - unless there is only a subset of the genes that they compare or something? Inga At 08:35 PM 9/19/2003 +0000, you wrote: >Yeah identicals are genetically the same. Blood type and everything. >HOwever there are many types of identical twins. THere are even >gentically idential twins that are boy/girl although the girls suffer >from 's Sundrome(I'm pretty sure that is what is is) when this >happens. > > >> >> Hi, >> >> I am just curious. It sure seems that a large number of RSS >kids >> >are >> >> fraternal twins. Does being a twin increase the odds of a >> >particular >> >> child being RSS. >> >> Conny >> > >> > >> > >> > >> > >> > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 20, 2003 Report Share Posted September 20, 2003 At the conference Dr. H said in her presentation that she believes now that there could be two causes of RSS, one being genetic, and the other being something happening in utero (poor environment, bad blood flow to one fetus, etc. ). The latter being why there are so many cases of twins where one has RSS and the other does not or both have it. Dr. H said she has identical twin patients where one has RSS and the other does not so this clearly shows it isn't always genetic. In the genetics presentation, the doctor did mention that IVF could cause gene imprinting errors (or something like that? I would have to confirm with my notes) and so this could also be a contributing factor as well as being older when the twins are conceived. Colin (RSS) & Hayden - 33 mo. twins and a baby-to-be in late December Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 20, 2003 Report Share Posted September 20, 2003 At the conference Dr. H said in her presentation that she believes now that there could be two causes of RSS, one being genetic, and the other being something happening in utero (poor environment, bad blood flow to one fetus, etc. ). The latter being why there are so many cases of twins where one has RSS and the other does not or both have it. Dr. H said she has identical twin patients where one has RSS and the other does not so this clearly shows it isn't always genetic. In the genetics presentation, the doctor did mention that IVF could cause gene imprinting errors (or something like that? I would have to confirm with my notes) and so this could also be a contributing factor as well as being older when the twins are conceived. Colin (RSS) & Hayden - 33 mo. twins and a baby-to-be in late December Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 20, 2003 Report Share Posted September 20, 2003 If one identical twin is diagnosed with RSS and the other is not, I would sure send them to LA to see Dr. Falk or to NY to see Harbison. I do not believe it is genetically possibly for this to happen. Identical twins have identical genetic makeups. Now, idiopathic SGA they might have, which can be confused with RSS. And it is possible that early in-utero placential problems could have caused SGA in one twin and not another? Possibly? I know that this is currently being studied. Dr. Falk and Harbison, at the convention this summer, gave a great summary of why there currently might be an increase in RSS (and other genetic problems) in twins that were a result of in-vitro. The very process of in-vitro results in an increased possibility of genetic problems -- Dr. Falk's handouts I believe have some info on this. > > > Hi, > > > I am just curious. It sure seems that a large number of RSS kids > > are > > > fraternal twins. Does being a twin increase the odds of a > > particular > > > child being RSS. > > > Conny Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 20, 2003 Report Share Posted September 20, 2003 If one identical twin is diagnosed with RSS and the other is not, I would sure send them to LA to see Dr. Falk or to NY to see Harbison. I do not believe it is genetically possibly for this to happen. Identical twins have identical genetic makeups. Now, idiopathic SGA they might have, which can be confused with RSS. And it is possible that early in-utero placential problems could have caused SGA in one twin and not another? Possibly? I know that this is currently being studied. Dr. Falk and Harbison, at the convention this summer, gave a great summary of why there currently might be an increase in RSS (and other genetic problems) in twins that were a result of in-vitro. The very process of in-vitro results in an increased possibility of genetic problems -- Dr. Falk's handouts I believe have some info on this. > > > Hi, > > > I am just curious. It sure seems that a large number of RSS kids > > are > > > fraternal twins. Does being a twin increase the odds of a > > particular > > > child being RSS. > > > Conny Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 20, 2003 Report Share Posted September 20, 2003 Yes, but it is possible after the twins separate, for something to change in the genetic code in one of them, but not the other... if this makes sense? There are also exceptions to every " rule " in biology... Darcy was tested for androgen insensitivity syndrome (or intersex) and some of these kids are born 100% female despite having male chromosomes. They are infertile, but can carry a child from a donor egg - sometimes they never know until they are tested for infertility. In s syndrome one of the X chromosomes is missing or badly formed - in the case of boy-girl twins my GUESS would be that one of the babies " loses " a Y-chromosome somehow after the twins separate. Steph > >> >> Hi, > >> >> I am just curious. It sure seems that a large number of RSS > >kids > >> >are > >> >> fraternal twins. Does being a twin increase the odds of a > >> >particular > >> >> child being RSS. > >> >> Conny > >> > > >> > > >> > > >> > > >> > > >> > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 20, 2003 Report Share Posted September 20, 2003 it would also be possible that the unfriendly uterine enviroment causes something genetic to go wrong... Darcy has a number of minor physical malformations other than his growth (and not RSS related) that nobody knows *why* happened. It's why the geneticists were so slow to come around to the RSS decision (2 years after our endo) they had trouble accepting that a child could have more than one problem, for some reason. ((HUGS)) Steph > At the conference Dr. H said in her presentation that she believes > now that there could be two causes of RSS, one being genetic, and the > other being something happening in utero (poor environment, bad blood > flow to one fetus, etc. ). The latter being why there are so many > cases of twins where one has RSS and the other does not or both have > it. Dr. H said she has identical twin patients where one has RSS and > the other does not so this clearly shows it isn't always genetic. In > the genetics presentation, the doctor did mention that IVF could > cause gene imprinting errors (or something like that? I would have to > confirm with my notes) and so this could also be a contributing > factor as well as being older when the twins are conceived. > > > Colin (RSS) & Hayden - 33 mo. twins and a baby-to-be in late December Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 20, 2003 Report Share Posted September 20, 2003 Jen, pasted below are 3 abstracts from Pub med on identical twins, one with RSS. I don't know their criteria for diagnosis - but I wouldn't discount the relationship between SGA and RSS, until we know for sure what " causes " RSS. Maybe there are two distinct sydromes,one genetic one caused by IUGR they just both happen to both " look " RSS. (my money is on the second cause for Darcy). ((HUGS)) Steph Fetal Diagn Ther. 1996 Jan-Feb;11(1):72-8. Related Articles, Links -Silver syndrome: an explanation for discordant growth in monozygotic twins. Sagot P, A, Talmant C, Pascal O, Winer N, Boog G. Service de Gynecologie-Obstetrique B, Centre Hospitalier Universitaire, Nantes, France. Severe intrauterine growth retardation and suggestive dysmorphic and malformation syndrome in 1 twin with a normal karyotype during a monozygotic, monochorionic pregnancy led to the diagnosis of discordant -Silver syndrome (RSS). Placental anomalies (velamentous cord insertion, single umbilical artery, placental hypotrophy) for the small-for-date twins and a twin-twin transfusion syndrome confirmed at 21 weeks of amenorrhea suggest that early hemodynamic disorders may reveal or trigger RSS which has been considered to be of genetic origin. The prognosis for RSS is favorable, except for diminished adult size (less than -2 standard deviations). PMID: 8719726 [PubMed - indexed for MEDLINE] Am J Med Genet. 1995 Aug 28;58(2):101-5. Related Articles, Links Monozygotic twins discordant for the -Silver syndrome. W, Popovich B, KL. Department of Pediatrics, Naval Hospital Pensacola, Florida, USA. -Silver syndrome (RSS) is a pattern of malformation characterized by intrauterine and postnatal growth retardation, limb asymmetry, triangular face, and hypospadias. We report on a patient, from a triplet pregnancy, who was one of identical male twins discordant for RSS. R.B. was a 710-g male born at 33 weeks of gestation, with hypospadias, chordee, and undescended testes. He had a normal 46,XY karyotype and no renal abnormalities. Female triplet A weighed 1,843 g, and male triplet B weighed 1,920 g. Both had normal physical findings and neonatal period. R.B. was first seen by us at age 6 7/12 years with short stature, triangular and asymmetric face, lower limb length discrepancy, and surgically repaired genital anomalies. Growth hormone testing results were normal. At age 8 7/12 years the brothers appeared physically identical except for size, with a height differential of 114.25 vs. 121.5 cm. Testing to establish biological zygosity was performed using VNTR (variable number tandem repeat) DNA probes YNH24 (D2S44), CMM101 (D14S13), EFD52 (D17S26), TBQ7 (D10S28), and 3'HVR (D16S85), PCR loci MCT118 (D1S80), and HLA-DQ alpha. These data indicate a > 99.99% probability of triplets B and C being monozygotic twins. While most occurrences of RSS are sporadic, familial cases suggesting autosomal dominance have been reported. Three other cases of probable monozygotic twins with RSS have been described. The significance of this confirmation of discordance in determining the cause of RSS is discussed. Publication Types: Review Review of Reported Cases PMID: 8533797 [PubMed - indexed for MEDLINE] Am J Med Genet. 1990 Dec;37(4):543-5. Related Articles, Links Monozygotic twins discordant for the -Silver syndrome. Samn M, K, Blumberg B. Department of Pediatrics, Children's Hospital of San Francisco, California 94118. -Silver syndrome is a disorder of unknown cause. A number of familial cases have suggested autosomal dominant inheritance. We report on monozygotic twins discordant for the -Silver syndrome. Our findings suggest that the cause of -Silver syndrome is not explained entirely by genetic factors. The possible role of the intrauterine environment as an etiologic component of -Silver syndrome is discussed. PMID: 2260605 [PubMed - indexed for MEDLINE] > If one identical twin is diagnosed with RSS and the other is not, I > would sure send them to LA to see Dr. Falk or to NY to see > Harbison. I do not believe it is genetically possibly for this to > happen. Identical twins have identical genetic makeups. > > Now, idiopathic SGA they might have, which can be confused with > RSS. And it is possible that early in-utero placential problems > could have caused SGA in one twin and not another? Possibly? I > know that this is currently being studied. > > Dr. Falk and Harbison, at the convention this summer, gave a great > summary of why there currently might be an increase in RSS (and > other genetic problems) in twins that were a result of in-vitro. > The very process of in-vitro results in an increased possibility of > genetic problems -- Dr. Falk's handouts I believe have some info on > this. > > > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 20, 2003 Report Share Posted September 20, 2003 Jen, pasted below are 3 abstracts from Pub med on identical twins, one with RSS. I don't know their criteria for diagnosis - but I wouldn't discount the relationship between SGA and RSS, until we know for sure what " causes " RSS. Maybe there are two distinct sydromes,one genetic one caused by IUGR they just both happen to both " look " RSS. (my money is on the second cause for Darcy). ((HUGS)) Steph Fetal Diagn Ther. 1996 Jan-Feb;11(1):72-8. Related Articles, Links -Silver syndrome: an explanation for discordant growth in monozygotic twins. Sagot P, A, Talmant C, Pascal O, Winer N, Boog G. Service de Gynecologie-Obstetrique B, Centre Hospitalier Universitaire, Nantes, France. Severe intrauterine growth retardation and suggestive dysmorphic and malformation syndrome in 1 twin with a normal karyotype during a monozygotic, monochorionic pregnancy led to the diagnosis of discordant -Silver syndrome (RSS). Placental anomalies (velamentous cord insertion, single umbilical artery, placental hypotrophy) for the small-for-date twins and a twin-twin transfusion syndrome confirmed at 21 weeks of amenorrhea suggest that early hemodynamic disorders may reveal or trigger RSS which has been considered to be of genetic origin. The prognosis for RSS is favorable, except for diminished adult size (less than -2 standard deviations). PMID: 8719726 [PubMed - indexed for MEDLINE] Am J Med Genet. 1995 Aug 28;58(2):101-5. Related Articles, Links Monozygotic twins discordant for the -Silver syndrome. W, Popovich B, KL. Department of Pediatrics, Naval Hospital Pensacola, Florida, USA. -Silver syndrome (RSS) is a pattern of malformation characterized by intrauterine and postnatal growth retardation, limb asymmetry, triangular face, and hypospadias. We report on a patient, from a triplet pregnancy, who was one of identical male twins discordant for RSS. R.B. was a 710-g male born at 33 weeks of gestation, with hypospadias, chordee, and undescended testes. He had a normal 46,XY karyotype and no renal abnormalities. Female triplet A weighed 1,843 g, and male triplet B weighed 1,920 g. Both had normal physical findings and neonatal period. R.B. was first seen by us at age 6 7/12 years with short stature, triangular and asymmetric face, lower limb length discrepancy, and surgically repaired genital anomalies. Growth hormone testing results were normal. At age 8 7/12 years the brothers appeared physically identical except for size, with a height differential of 114.25 vs. 121.5 cm. Testing to establish biological zygosity was performed using VNTR (variable number tandem repeat) DNA probes YNH24 (D2S44), CMM101 (D14S13), EFD52 (D17S26), TBQ7 (D10S28), and 3'HVR (D16S85), PCR loci MCT118 (D1S80), and HLA-DQ alpha. These data indicate a > 99.99% probability of triplets B and C being monozygotic twins. While most occurrences of RSS are sporadic, familial cases suggesting autosomal dominance have been reported. Three other cases of probable monozygotic twins with RSS have been described. The significance of this confirmation of discordance in determining the cause of RSS is discussed. Publication Types: Review Review of Reported Cases PMID: 8533797 [PubMed - indexed for MEDLINE] Am J Med Genet. 1990 Dec;37(4):543-5. Related Articles, Links Monozygotic twins discordant for the -Silver syndrome. Samn M, K, Blumberg B. Department of Pediatrics, Children's Hospital of San Francisco, California 94118. -Silver syndrome is a disorder of unknown cause. A number of familial cases have suggested autosomal dominant inheritance. We report on monozygotic twins discordant for the -Silver syndrome. Our findings suggest that the cause of -Silver syndrome is not explained entirely by genetic factors. The possible role of the intrauterine environment as an etiologic component of -Silver syndrome is discussed. PMID: 2260605 [PubMed - indexed for MEDLINE] > If one identical twin is diagnosed with RSS and the other is not, I > would sure send them to LA to see Dr. Falk or to NY to see > Harbison. I do not believe it is genetically possibly for this to > happen. Identical twins have identical genetic makeups. > > Now, idiopathic SGA they might have, which can be confused with > RSS. And it is possible that early in-utero placential problems > could have caused SGA in one twin and not another? Possibly? I > know that this is currently being studied. > > Dr. Falk and Harbison, at the convention this summer, gave a great > summary of why there currently might be an increase in RSS (and > other genetic problems) in twins that were a result of in-vitro. > The very process of in-vitro results in an increased possibility of > genetic problems -- Dr. Falk's handouts I believe have some info on > this. > > > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 21, 2003 Report Share Posted September 21, 2003 Those were really cool to read!! Thanks for sharing them!! > > If one identical twin is diagnosed with RSS and the other is not, I > > would sure send them to LA to see Dr. Falk or to NY to see > > Harbison. I do not believe it is genetically possibly for this to > > happen. Identical twins have identical genetic makeups. > > > > Now, idiopathic SGA they might have, which can be confused with > > RSS. And it is possible that early in-utero placential problems > > could have caused SGA in one twin and not another? Possibly? I > > know that this is currently being studied. > > > > Dr. Falk and Harbison, at the convention this summer, gave a great > > summary of why there currently might be an increase in RSS (and > > other genetic problems) in twins that were a result of in-vitro. > > The very process of in-vitro results in an increased possibility of > > genetic problems -- Dr. Falk's handouts I believe have some info on > > this. > > > > > > > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 21, 2003 Report Share Posted September 21, 2003 Those were really cool to read!! Thanks for sharing them!! > > If one identical twin is diagnosed with RSS and the other is not, I > > would sure send them to LA to see Dr. Falk or to NY to see > > Harbison. I do not believe it is genetically possibly for this to > > happen. Identical twins have identical genetic makeups. > > > > Now, idiopathic SGA they might have, which can be confused with > > RSS. And it is possible that early in-utero placential problems > > could have caused SGA in one twin and not another? Possibly? I > > know that this is currently being studied. > > > > Dr. Falk and Harbison, at the convention this summer, gave a great > > summary of why there currently might be an increase in RSS (and > > other genetic problems) in twins that were a result of in-vitro. > > The very process of in-vitro results in an increased possibility of > > genetic problems -- Dr. Falk's handouts I believe have some info on > > this. > > > > > > > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 21, 2003 Report Share Posted September 21, 2003 Hi Steph, I still cannot understand how a boy/girl combination can be considered genetically identical. If the twins come from the same egg, then one of them undergoes a change in the genetic code after splitting, how can they possibly be genetically identical. One has the XX chromosome and the other the XY? ne > > >> >> Hi, > > >> >> I am just curious. It sure seems that a large number of RSS > > >kids > > >> >are > > >> >> fraternal twins. Does being a twin increase the odds of a > > >> >particular > > >> >> child being RSS. > > >> >> Conny > > >> > > > >> > > > >> > > > >> > > > >> > > > >> > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 21, 2003 Report Share Posted September 21, 2003 No, one has one X chromosome ('s Syndrome) one has XY, all their other genetic material is identical. I guess they are not identical anymore, but they are still monozygotic. ((HUGS)) Steph > > > >> >> Hi, > > > >> >> I am just curious. It sure seems that a large number of > RSS > > > >kids > > > >> >are > > > >> >> fraternal twins. Does being a twin increase the odds of a > > > >> >particular > > > >> >> child being RSS. > > > >> >> Conny > > > >> > > > > >> > > > > >> > > > > >> > > > > >> > > > > >> > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 22, 2003 Report Share Posted September 22, 2003 I wonder - is the sex determined just by the egg or does the sperm have an influence? Is an identical twin when an egg splits and then two sperm fertilize them, or when a fertized egg splits? The fraternal twins are when there are two eggs... If there are two sperms involved, could this explain having RSS in one and not the other? Also, if it is the kind of RSS where there is a duplicating of the maternal info, perhaps the process of joining with the sperm is somehow different in both and that process went wrong in the RSS one, not the sperm and egg themselves? Inga At 10:52 AM 9/21/2003 +0000, you wrote: > > >Hi Steph, >I still cannot understand how a boy/girl combination can be >considered genetically identical. >If the twins come from the same egg, then one of them undergoes a >change in the genetic code after splitting, how can they possibly be >genetically identical. One has the XX chromosome and the other the XY? >ne > > >> > >> >> Hi, >> > >> >> I am just curious. It sure seems that a large number of >RSS >> > >kids >> > >> >are >> > >> >> fraternal twins. Does being a twin increase the odds of a >> > >> >particular >> > >> >> child being RSS. >> > >> >> Conny >> > >> > >> > >> > >> > >> > >> > >> > >> > >> > >> > >> > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 22, 2003 Report Share Posted September 22, 2003 Steph, What does 'monoqygotic' mean? Inga At 10:55 PM 9/21/2003 +0000, you wrote: >No, one has one X chromosome ('s Syndrome) one has XY, all >their other genetic material is identical. I guess they are not >identical anymore, but they are still monozygotic. >((HUGS)) >Steph > > >> > > >> >> Hi, >> > > >> >> I am just curious. It sure seems that a large number of >> RSS >> > > >kids >> > > >> >are >> > > >> >> fraternal twins. Does being a twin increase the odds of >a >> > > >> >particular >> > > >> >> child being RSS. >> > > >> >> Conny >> > > >> > >> > > >> > >> > > >> > >> > > >> > >> > > >> > >> > > >> > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 22, 2003 Report Share Posted September 22, 2003 Hi Inga, The sperm determines the sex of the child. In the case of twins, the egg is fertilized, and the splits into two separate entities. The egg can only be fertilized by one sperm as far as I know. Hope this helps. Pat (g-ma to , RSS, 21 months, 18# 2oz, 29 " , Prevacid, Zantac, Singulair, GT) Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 22, 2003 Report Share Posted September 22, 2003 Hi Inga, I had a little extra time today, so I looked it up on the internet. These are the definitions they gave me. Definition: A type of twins derived from a single (mono) egg (zygote). Monozygotic twins form when a single fertilized egg splits into two embryos. Because the twins share the same DNA set, they tend to have similar features. Also Known As: Identical Twins Definition: Derived from a two (di) eggs (zygote). Dizygotic twins form when two separate eggs are fertilized by separate sperm. Also Known As: Fraternal Twins I guess we get to learn something new every day here! LOL Hope this helps. Pat (g-ma to , RSS, 21 months, 18# 2oz, 29 " , Prevacid, Zantac, Singulair, GT) Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 22, 2003 Report Share Posted September 22, 2003 lol... when reading through the stuff on twins the other day one of the articles suggested it was possible for an egg to split before fertilisation, and each egg by fertilized by a different sperm; the article went on to say this hadn't been proven. Normally the split occurs after the egg is fertilized. I don't know if the RSS twins were positive for UPD7 or not, it didn't say in the abstract, so I guess anything is possible. Sperm determines gender. Every egg has one X chromosome, the sperm has either an X or a Y chromosome, so when they join it's either XX or XY. ((HUGS)) Steph > >> > >> >> Hi, > >> > >> >> I am just curious. It sure seems that a large number of > >RSS > >> > >kids > >> > >> >are > >> > >> >> fraternal twins. Does being a twin increase the odds of a > >> > >> >particular > >> > >> >> child being RSS. > >> > >> >> Conny > >> > >> > > >> > >> > > >> > >> > > >> > >> > > >> > >> > > >> > >> > Quote Link to comment Share on other sites More sharing options...
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