What exactly is Identical Twins?I need a logical answer.?

Question

I need to know what exactly Identical twins are.I need to know facts and examples.Facts like How can you tell them apart.How they form instead of one fetus to two.Whats so special about identical twins,and etc.Please give me a smart answer.

Answer 1

try this website,.... they have some great stuf on twins....

http://www.twinsworld.com/stats.html

Answer 2

It's really not clear how the fertilized cell decides to split into 2 separate cells rather than continuing to develop as a 2-cell entity. This is what makes them special. Fraternal twins form because there are two eggs available, and both get fertilized and develop. I don't have the source, but I recall that fraternal twins occur in about 1 out of 43 births, although I believe there is some trend that some families are more likely to have twins than others. Identical twins are much less likely, and are always the same sex, while fraternal twins don't necessarily have to be of the same sex. Due to sublte changes in development to a fetus from a single cell, there are some differences in the twins if someone really wants to look for them.

Answer 3

Identical twins are formed when the newly fertilized embryo ( only a few cells) splits into 2. Each one is an identical copy of the other, right down to their DNA. Often they cant be told apart until they begin to grow up. one of my identical twin friends got a scar on her neck, and that was the only way I could tell them apart.

Answer 4

twins that came from the same egg meaning they split making them genetically identical(doesnt mean they look the same) and the twins must b the same sex

Answer 5

Twins in animal biology is a form of multiple birth in which the mother gives birth to two offspring from the same pregnancy, some of the same gender, others of opposite.

There are estimated to be approximately 125 million twins and triplets in the world, and just 10 million identical twins.[citation needed]

Triplets refers to three offspring from the same pregnancy. The general term for more than one offspring from the same pregnancy is multiples. A fetus alone in the womb is called a singleton.

Human twins are two individuals who have shared the uterus during a single pregnancy and are usually, but not necessarily, born in close succession. Due to the limited size of the mother's womb, multiple pregnancies are much less likely to carry to full term than singleton births, with twin pregnancies lasting only 37 weeks on average, 3 weeks less than full term. Since premature births can have health consequences for the babies, twin births are often handled with special precautions.

[edit] Identical twins
Identical twins occur when a single egg is fertilized to form one zygote (monozygotic) which then divides into two separate embryos. Although their traits and physical appearances are not exactly the same due to environmental conditions in both the womb and outside the womb, they do have the same DNA. This is not considered to be a hereditary trait, but rather an anomaly that occurs in birthing at a rate of about 3 in every 1000 deliveries worldwide,[2] regardless of ethnic background. The two embryos develop into fetuses sharing the same womb. When one egg is fertilized by one sperm cell, and then divides and separates, two identical cells will result. Depending on the stage at which the zygote divides, identical twins may share the same amnion (or in the same amnion and placenta/chorion), which can cause complications in pregnancy. For example, the umbilical cords of monoamniotic twins can become entangled, reducing or interrupting the blood supply to the developing fetus. About 50% of mono-mono twins die from umbilical cord entanglement. Monochorionic twins, sharing one placenta, usually also share the placental blood supply. These twins may develop such that blood passes disproportionately from one twin to the other through connecting blood vessels within their shared placenta, leading to twin-to-twin transfusion syndrome.

Monozygotic twins are genetically identical (unless there has been a mutation in development) and they are the same gender. (On extremely rare occasions, an original XXY zygote may form monozygotic boy/girl twins by dropping the Y chromosome for one twin and the extra X chromosome for the other.) Monozygotic twins generally look alike. Fine physical details such as fingerprints will differ. As they mature, identical twins often become less alike because of lifestyle choices or external influences. Genetically speaking, the children of identical twins are half-siblings rather than cousins. It is estimated that there are around 125 million identical twins and triplets in the world.

The likelihood of a single fertilization resulting in identical twins appears to be a random event, not a hereditary trait, and is uniformly distributed in all populations around the world.[citation needed] This is in marked contrast to fraternal twinning which ranges from about 6 per thousand births in Japan (almost similar to the rate of identical twins, which is around 4-5) to 15 and more per thousand in some parts of India[3] (and up to 24 in the US, which might mainly be due to IVF, in vitro fertilization). The exact cause for the splitting of a zygote or 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 belief that many behaviors are derived from genes.

Identical twins have identical DNA but differing environmental influences throughout their lives affect which genes are switched on or off. This is called epigenetic modification. A study of 80 pairs of human twins ranging in age from 3 to 74 showed that the youngest twins have relatively few epigenetic differences. The number of epigenetic differences between identical twins increases with age. 50-year-old twins had over three times the epigenetic difference of 3-year-old twins. Twins who had spent their lives apart (such as those adopted by two different sets of parents at birth) had the greatest difference. [4]. However, certain characteristics become more alike as twins age, such as IQ and personality [5] [6]. This phenomenon illustrates that genetics play a dominant role in many aspects of human characteristics and behaviour

Answer 6

http://en.wikipedia.org/wiki/Fraternal_twins