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Mika Kenj

on 10 March 2014

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Transcript of Twin

is the degree of identity in the genome of twins. There are five common variations of twinning.
most common variations are all
dizygotic (fraternal):
*Male–female twins
are the most common result, 50 percent of dizygotic twins and the most common grouping of twins.
*Female–female dizygotic twins
(sometimes called "sororal twins")
*Male–male dizygotic twins
The other
variations are
monozygotic ("identical") twins:
monozygotic twins
monozygotic twins (less common)
1. In 1980, one in every 53 babies born in the United States was a twin. By 2009, that number had risen to one in 30, which means that over three decades, the twin birth rate (number of twins per 1,000 births) rose 76%.

2. The chances of having a twin pregnancy is increased by maternal age (30+).

3. There is a "twin gene" - fraternal twining, which is the result of a woman releasing more than one egg at the same time, is genetically predisposed.

4. Identical twins are the result of a random split of a single egg and cannot be genetically predisposed.

5. Male twins will not have twins unless their wives have the ability to produce two eggs.

6. Identical twins share the same DNA but do not have the same fingerprints.

7. About 1 in 250 pregnancies results in identical twins.

8. 22 % percent of twins are left handed, compared to 10% in singletons.

9. Fraternal twin girls have twice the chance of giving birth to twins than singletons.

10. Vanishing twin syndrome- 15-20% percent of all twin pregnancies will miscarry one fetus.

11. Some estimates suggest 1 in 8 people started life as a twin while 1 in 70 actually are a twin.

12. Once you have fraternal twins, you are 3 to 4 times more likely to have another set!

13. Nigeria has the highest rate of multiple births and more identical twins.

14. China has the lowest rate for multiple births averaging 1 in 300.

15. A study shows vegans are five times less likely to have twins than women who consume diary.

16. For polar bears, twins aren't unusual at all. In fact, they most commonly give birth to twins, and rarely deliver single cubs or triplets.

17. Twins bond in the womb. By examining 3D ultrasound images, a study in Padova, Italy found that fetuses start deliberately interacting at 14 weeks.

18. 40% of twins invent their own language.

19. They tend to be early - over 50% of twins are born before 37 weeks.

20. The average birth weight for a twin is 5lbs, 5 oz.

- two offspring produced by the same pregnancy.
They can be the same or different sex.

Monozygotic ("identical")
, meaning that they develop from one zygote that splits and forms two embryos.
*They have identical genes.
*Identical twins make up 1/3rd of all twins.
Dizygotic ("fraternal")
, meaning that they develop from two eggs, each fertilized by separate sperm cells.
Fraternal twins often have notable physical differences ( different height, weight, hair colour etc.
Fraternal twins can therefore be different genders.
roughly 66% of all twins are fraternal.

Identical twins, occur when a single egg is fertilized to form one zygote which then divides into two separate embryos.
The two embryos develop into fetuses sharing the same womb. And two identical cells will result.
If the zygote splits after the first two days after fertilization each cell may develop separately its own placenta and its own sac.

Conjoined twins
are joined at some region of their bodies. The many different types of conjoined twins are classified by the area where the attachment is located:
It results when an embryo start to divide but fails to complete the process, and the result is not quite two children
The twins originate from a single fertilized egg, so they are always identical and of the same sex.
It is believed that the first 13th and 15th days after fertilization the malformation occurs

Fraternal twins:, usually occur when two fertilized eggs are implanted in the uterine wall at the same time. When two eggs are independently fertilized by two different sperm cells.

other types
Polar Body Twins
: They can be considered half identical. It occurs when the mother’s egg splits before fertilization. Therefore, the twins will share the same genetic traits as their mother and different traits from the father ( as different sperm fertilize one egg that has split).

Mirror Image Twins
: Occurs when the split of the egg occurs late. The twins often acquire “reverse asymmetric features”. This could mean that a birthmark on one twin can appear exact on the other but on the opposite side ( Hence the mirror image). Only one quarter of monozygotic twins are mirror image twins.

Parasitic Twins
: It is a form of conjoined twin where one, less developed, small and weaker twin depends on a stronger twin.

- back-to-back, joined at the rump (about 19 percent)

- joined sacrum to sacrum (about six percent)

- connected at the head (about two percent)

- one upper body with two lower bodies (including the abdomen, pelvis and legs)

- joined at the chest; may share a single heart or have some cardiac connection; some organs in the abdominal region may be malformed (about 40 percent)

- joined at the chest (about 33 percent)

- back-to-back, joined along the spine above the sacrum


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