For other uses, see Twin (disambiguation).
Fraternal twin boys in the tub
Twins in animal biology is twin a case of multiple birth in tins which the mother gives birth to two offspring from the same pregnancy.
Human twins are wins two individuals who have shared the uterus during a single pregnancy and are usually, twinz but not necessarily, born in close succession. A fetus alone in the womb is called a twis singleton. Due to the limited size twinx of the mother's womb, multiple pregnancies are much less likely to carry teins to full term than singleton births, with twin pregnancies usually lasting around 34 to 36 weeks. Since twims premature births can have health consequences for the babies, twiins twin births are often handled with special precautions.
There are twinns five variations of twinning that occur commonly in the world. rwins The three most common variations are all fraternal: (1) boy-girl twins are the most common result, at about 40% of ttwins all twins born; tiwns (2) girl fraternal twins; (3) boy fraternal twins. The last two are identical: twons (4) girl identical twins and (5) (least common) boy identical twins.
Twinning is common twisn in many animal species, such as cats, sheep, and ferrets. The incidence of twns twinning among cattle is about 1-4%, and research is underway to improve the odds of twinning, which can olsen twins be more twin towers profitable for the breeder if complications can be sidestepped or managed.
- Note: Sometimes multiple births may involve more than two fetuses. See twins multiple birth for more information.
- 1 Types of ying yang twins twins
- 1.1 Fraternal milton twins twins
- 1.2 Identical twins
- 1.3 Mirror carlson twins twins
- 1.4 Polar twins
- 2 Complications of twin pregnancy
- 2.1 Vanishing minnesota twins twins
- 2.2 Conjoined twins
- 2.3 Parasitic simpson twins twins
- 2.4 Partial Molar twins
- 2.5 Miscarried twin
- 3 Human aphex twin twins
- 3.1 Predisposing factors
- 3.2 Human taylor twins twin studies
- 3.3 Unusual olson twins twinnings
- 4 See also
- 5 Notes
- 6 References
- 7 External conjoined twins links
Types of twins
Fraternal twins (commonly known as "non-identical twins") usually brewer twins occur when two fertilized eggs are implanted in the uterine wall at the same time. The two twin eggs form two zygotes, and these twins are therefore identical twins also known as dizygotic as well as "biovular" twins. When two eggs are bucci twins independently fertilized by two different sperm cells, fraternal hot twins twins result.
Dizygotic twins, like any other siblings, have a very small chance of having twin sisters kissing the exact same chromosome profile, but most likely have a number of different chromosomes that distinguish them. Like any other twin sisters siblings, fraternal twins may look very similar, particularly barbie twins given that they are the twin towers falling same age. However, fraternal twins may also look very different from each other. They may be a twin peaks different sex or the same sex. Mixed-race twins, or twins born to parents of mixed racial origin, can vary siamese twins considerably in olsen twins thong their skin colouration and other features.
Studies show that there is a genetic basis the twin towers for fraternal twinning. However, it is only the female partner olsen twins fakes that has any influence on the chances of having fraternal twins as the male cannot make shake ying yang twins her release more than one ovum. Fraternal twinning ranges from 1 or 2 per ying yang twins shake thousand births in Japan (similar to the rate of identical twin girls twins) to 14 and more per thousand in some African twin falls idaho real estate states.
Fraternals are also more common pregnant with twins for older mothers, with twinning rates doubling twins baseball in mothers over the age of 35.
With the advent of technologies and techniques to assist women in getting pregnant, the thompson twins rate of fraternals has increased markedly. For example, the olsen twins in New York City's Upper East Side there were 3,707 twin births in 1995; there fake olsen twins were 4,153 in 2003; herrin twins and there were 4,655 in 2004. Triplet births have also risen, from 60 in bernaola twins 1995 to 299 in 2004.
Identical twins occur when a single bentley twins egg is fertilized to form one zygote (monozygotic) which mn twins then divides into two separate embryos. This is not considered to be a hereditary trait, but rather an anomaly that occurs in yin yang twins birthing at twin mattress a rate of about 1:150 births worldwide, regardless of ethnic background. The twins kissing two embryos develop into fetuses sharing the same womb. When one cocteau twins egg is fertilized by one sperm cell, and then divides and separates, two identical cells will result. Depending on the stage twin paradox theory at which the zygote divides, identical twins may share fraternal twins the same amnion (or in the same amnion and placenta/chorion), which can twin pregnancy cause complications in pregnancy. For example, the umbilical cords of monoamniotic twins can become entangled, reducing or bush twins interrupting the blood supply to the developing fetus. About 50% onegai twins of mono-mono twins die from umbilical cord twin beds entanglement. Monochorionic twins, sharing one placenta, usually also share the placental blood supply. These minnesota twins baseball twins may develop such that blood passes disproportionately from one twin to the other through twin boys connecting blood vessels within their shared placenta, leading to twin-to-twin transfusion syndrome.
Monozygotic twins twin falls idaho are genetically identical (unless there has been hall twins a mutation in development) and they are the same gender. (On extremely rare occasions, an original XXY zygote may home makeover twin bridges form twin tower monozygotic boy/girl twins by dropping the Y chromosome for one twin and the extra X chromosome for the home redesign twin bridges other.) Monozygotic twins generally look alike. Fine physical details such minnesota twins tickets as fingerprints will differ. As they mature, identical twins often become less alike because of pregnant twins lifestyle choices or external influences. Genetically speaking, the children of identical twins are half-siblings rather than mario twins cousins.
The likelihood of a single fertilization resulting in ying yang twins wait identical twins is a random event, not tenison twins a hereditary trait, and is uniformly distributed in all populations around petronas twin tower the world. This is in marked contrast to fraternal twinning which ranges from 1 or 2 per thousand births in Japan twin angels (similar twin paradox to the rate of identical twins) to 14 and more per thousand in some African states
. The exact cause for the olsen twin in swimsuits splitting of a zygote or olsen twins bikini embryo is unknown.
Studies have shown that identical twins reared in different environments share similar personality traits, mannerisms, job choices, attitudes, and interests
. These findings add to the carlson twins gallery belief that many behaviors are derived from genes.
Identical twins have identical DNA but differing environmental influences throughout their lives costello twins affect which genes are twin babies switched on or off. This is called epigenetic modification. A study of 80 pairs of hensel twins human twins ranging in age from 3 to 74 showed that the youngest twins have relatively few epigenetic olsen twins kiss differences. The number of differences between identical twins increases with age. 50-year-old doublemint twins twins had over three times the epigenetic difference of 3-year-old twins. Twins olsen twins fake who had spent their lives twin bed apart (such as those adopted by two different sets of parents at birth) had the greatest difference. ying yang twins mp3 (Fraga, et al., 2005).
Some monozygotic twins are newborn twins known as "mirror twins" or mirror image twins. These are identical twins with opposite twin engine features, that is, one may twin falls real estate be right-handed and the other left-; mirrored hair curls, etc. This condition is comparatively hilton twins rare in humans. It results from a late split of the fertilized egg at twin flat sheets around 9-12 days. One mirror may have situs inversus, where some or all of twin falls the organs are on the opposite side morrell twins of the body, such as the heart on the right (dextrocardia). Such conditions are usually associated parasitic twins with a higher incidence of other birth toyota supra twin turbo defects.
Polar twins are monozygotic but develop differently, due to different genes being activated. These "half-identical twins" twin brothers may occur when one sperm fertilizes the milton twins the egg, while another fertilizes a polar body.
Complications of twin jogging stroller twin pregnancy
Researchers suspect that as many as aphex twin mp3 1 in 8 pregnancies start out as multiples, but only a single fetus is brought group x mario twins to full term, because the other has died very early twin towers video in the pregnancy and not been detected or recorded. Early twins mp3 obstetric ultrasonography exams sometimes reveal an "extra" fetus, which fails to develop and instead disintegrates and olson twins in a thong vanishes. This is known as amelia earhart twin engine vanishing twin syndrome.
Conjoined twins, (or "Siamese twins") are monozygotic twins, whose bodies are joined together at ying yang twins salt shaker birth. This occurs where the single zygote of identical twins aphex twin windowlicker fails to separate completely, and the zygote starts to split after day 13 following fertilization. dolphin twin sheets This condition occurs in about 1 in 50,000 human pregnancies. Most conjoined twin cities special relativity twin paradox twins are now evaluated for surgery to attempt to separate them into separate functional bodies. The degree of difficulty rises if a pictures of the twin towers vital organ or twin towers attack structure is shared between twins, such as brain, heart or liver.
A chimera is an ordinary person discount ticket brokers twin cities or animal except that some of his or her parts actually came from his or minnesota twins logo her twin. A chimera may arise either from identical twin fetuses (where it would be impossible twin lion chinese restaurant to detect), or from potter twins dizygotic fetuses, which can be identified by chromosomal aphex twin come to daddy comparisons from various parts of the body. The number of cells derived from each fetus can vary from one part of hemp twin bedding the body to another, and often leads to characteristic mosaicism skin colouration in human chimeras. twin flames A chimera may be a hermaphrodite, composed of cells wonder twins from a male twin and a female twin.
Sometimes one twin fetus olsen twins pictures will fail to develop completely and continue to cause problems for twin tower jumpers its surviving twin. One fetus acts as a parasite towards the other.
Sometimes the parasitic twin becomes an wait ying yang twins almost indistinguishable part of the other.
Partial Molar twins
A very rare type of parasitic twinning is where a single viable twin twin baby stroller is endangered when the other zygote become cancerous, or molar. This extra long twin sheets means that the molar zygote's cellular jesus twins division continues unchecked, resulting in a cancerous growth that overtakes twins french kissing the viable fetus.
Occasionally, a female will suffer a miscarriage early in pregnancy, yet the pregnancy will continue; one twin was twins galleries miscarried but the other was able to human chimera fused twins be carried to term. This occurrence is similar to the vanishing twin syndrome.
Historically, about 1 in 80 human olsen twins shower births (1.25%) has been the result of a twin pregnancy. The rate of twinning varies greatly among ethnic groups, thong the olsen twins ranging as high as twin turbo about 6% for the Yoruba or 10% for a tiny Brazilian village. The the twins widespread use of fertility drugs causing hyperovulation (stimulated release of multiple eggs by the mother) has yang yang twins caused what 300zx twin turbo some call an "epidemic of multiple births". In 2001, for the first time ever in the US, coors twins the twinning rate exceeded 3% of all births. Thus, approximately 5.8% of children born in the love twins US in 2001 the olson twins were twins.
Nevertheless, the rate of identical twins remains at about 1 in 250 across black twins the globe, further suggesting that pregnancies resulting in identical twins occur randomly.
The cause of monozygotic twinning is halftime ying yang twins unknown.
Dizygotic twin pregnancies are slightly more likely when staging twin bridges the following factors are present in the woman:
- She is of African descent (especially Yoruba)
- She is between stroller twin the age of 30 and 40 years
- She is greater than average height twin grove campground and weight
- She has had several previous pregnancies.
Women undergoing certain fertility treatments may ying yang twins lyrics have a greater chance of dizygotic multiple births. This can vary depending japanese twins on what types of fertility treatments are used. twin cities real estate With in vitro fertilization (IVF), this is primarily due to the insertion of multiple embryos modular homes for sale in twin cities,mn. into the uterus. Some other treatments such as the drug naughty twins Clomid can stimulate a woman to release multiple eggs, allowing the carlson twins the possibility of multiples. Many fertility treatments ying yang twins badd have no effect on the likelihood of multiple births.
There is also speculation that the West African predisposition to twinning is due anime twins to the large amount of yams in their diet. They contain phytoestrogen, which may stimulate male twins the ovaries.
Human twin studies
Twin studies are studies that assess identical (monozygotic) twins for twin size mattress medical, genetic, or psychological characteristics to try to isolate genetic influence from environmental influence. ying yang twins naggin Twins that have been separated early in life and raised in separate households aphex twin window licker are especially sought-after for these studies, which have been invaluable olsen twin in the exploration of human nature.
There are some patterns twin grove park campground of twinning that are exceedingly rare: while they have twin sleeper chair been reported to happen, they are so unusual that most obstetricians home staging northern california twin bridges or midwives may go their entire careers without the love twins encountering a single case.
Among fraternal twins, in rare cases, the eggs are fertilized at different twin grove park times with two or more acts of sexual intercourse, either within one menstrual cycle (superfecundation) or, twin towers pictures even more rarely, later on in the pregnancy (superfetation). This can twin souls lead to the possibility of a travel system stroller for twins woman carrying fraternal twins with different fathers (that is, half-siblings). This phenomenon is known as heteropaternal superfecundation. One 1992 twin stroller study estimates that the frequency of heteropaternal superfecundation among dizygotic twins whose parents were involved in home staging twin bridges paternity suits was approximately 2.4%; see the references section, below, for twins tickets more details.
Among monozygotic twins, in extremely rare cases, twins have disaster of twin towers been born with opposite staging home twin bridges sexes (one male, one female). The probability of this is so vanishingly small (only 3 documented casesin utero multiples famous twins are not monozygotic. When twin cities homes for sale monozygotic twins are born with different genders it is because of chromosomal birth defects. In this case, although the twins ying yang twins halftime did come from the same egg, it is incorrect 9/11 twin towers to refer to them as genetically identical, since they have different karyotypes.
) that multiples having different genders is universally accepted as a sound basis for a clinical determination that
- Cloning (with reference to identical twins)
- List of twins
- Multiple birth
- NICU (Neonatal twin cities home for sale Intensive Care Unit)
- ^ U. twin towers jumpers Matte et al. Study on possible increase in twinning rate buying selling listings home twin falls idaho real estate at a small village in south Brazil. Acta Genet Med Gemellol (Roma). 45(4), 1996. 431–437.
- Fraga onegai twins mp3 MF, Ballestar E, salt shaker ying yang twins Paz MF, Ropero S, Setien F, Ballestar ML, Heine-Suner D, Cigudosa JC, Urioste M, twin bedding Benitez J, Boix-Chornet M, Sanchez-Aguilera A, Ling C, Carlsson E, Poulsen P, Vaag A, twin vee Stephan Z, Spector TD, Wu YZ, Plass C, Esteller M (2005). "Epigenetic differences arise during the video of the twin towers lifetime of monozygotic twins". Proceedings of the National Academy of Sciences 102 (30): 10413–10414. PMID how old are the olsen twins 16009939.
- Nieuwint twin baby gifts A, Van Zalen-Sprock R, Hummel P, Pals G, Van Vugt J, Van Der Harten university of minnesota twin cities H, Heins Y, Madan K. (1999). "'Identical' twins with discordant karyotypes". Prenatal Diagnosis 19 (1): 72-6. 9-11 twin towers PMID 10073913.
- Wenk RE, Houtz T, Brooks M, Chiafari FA (1992). "How extra long twin bedding frequent is heteropaternal superfecundation?". Acta geneticae medicae et gemellologiae 41 (1): 43-7. PMID metal gear solid the twin snakes 1488855.
- Girela E, Lorente JA, Alvarez JC, Rodrigo MD, Lorent M, Villaneuva E (1997). "Indisputable double paternity in dizygous twins". Fertility and Sterility 67 (6): 1159-61. PMID 9176461.
- Twins Facts
- Twins website, statistics
- About twins statistics
- The Biology of Mirror-Image Twins
- Psychology Today article
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