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Twin can be identical , fraternal and apparently semi - identical , scientist now report .

investigator discovered similitude who are identical on their mom ’s side of the equation but share only one-half theirgenesfrom papa .

dna, dna strand

Here ’s how it happened : Twospermcells fertilized one egg — an event assumed to be very rare — then split up into two embryos .

" Their similarity is somewhere between monovular and fraternal twins , " tell geneticist Vivienne Souter , of the Banner Good Samaritan Medical Center in Phoenix , Arizona . " It makes me enquire whether the current classification of twins is an simplism . "

The determination , detailed in the Journal of Human Genetics , was report today by news@nature.com , the on-line site of the journal Nature .

A stock photograph of four surgeons in discussion before an operation.

Identicaltwinsare created when one inseminate egg split into two embryos . They share the same placenta and are always of the same sex . Fraternal twins ensue from two egg being fertilise at the same time , each by a unlike spermatozoon . Each has its own placenta , and they can be the same sex activity or not .

The semi - monovular twins only came to the attention of Souter and her colleague because one had ambiguous genital organ . The child was born a " true intersex " with both ovarian and testicular tissue . The other Twin Falls is a male , anatomically .

The similitude are now tot , according to the study . They were conceive and stomach normally and appear to be mentally normal and are growing normally .

African American twin sisters wearing headphones enjoying music in the park, wearing jackets because of the cold.

an illustration of an ichthyosaur swimming underwater with ancient fish

a pregnant woman touches her belly

A close-up portrait of orange cat looking at the camera.

Indigenous San people walk through the landscape in Botswana, Africa.

magic mushroom, mushroom, shroom

A biotech company released thousands of genetically-modified <em>Aedes aegypti</em> mosquitoes in Brazil in an effort to reduce the number of disease-carrying mosquitoes. New findings suggest the genetically-modified insects are passing some genes to the native ones.

An artist�s rendering show�s the first-ever portrait of a Denisovan woman, recreated from an ancient DNA sample.

An illustration of IVF.

This famous photograph of Nessie from 1934 turned out to be a hoax created with a toy submarine and a fake "sea monster" body.

An image comparing the relative sizes of our solar system�s known dwarf planets, including the newly discovered 2017 OF201

an illustration showing a large disk of material around a star

a person holds a GLP-1 injector

A man with light skin and dark hair and beard leans back in a wooden boat, rowing with oars into the sea

an MRI scan of a brain

A photograph of two of Colossal�s genetically engineered wolves as pups.

Radiation Detection Manager Jeff Carey, with Southern California Edison, takes a radiation reading at the dry storage area during a tour of the shuttered San Onofre Nuclear Generating Station south of San Clemente, CA