My living reflection: The identical 'mirror image' twins born with opposite features
02:30 GMT, 29 May 2012
One half of a pair of identical twins has told of how she was genetically formed as an exact opposite to her sister.
Erin Hatfield, a 23-year-old from Augusta, Georgia, has taken to the social networking site Reddit to discuss how the placement of her organs and facial features mirror those of her sister Ashley.
The sisters are classed as 'mirror image' twins which is a term used to describe identical twins who share the same DNA but develop asymmetric features.
Similar: Erin Hatfield, right, has told of how she and her sister Ashley, left, are identical 'mirror twins'. Their facial features reflect each others. For example, Erin's left eye is the same as Ashley's right eye
The twins are monozygotic, which means they were formed from a single fertilised egg like any other identical twins.
Although experts claim that organs remain in the usual areas in the case of 'mirror image' twins, Erin claimed that doctors have advised her otherwise.
She wrote: 'We have always been told that our organs were shifted. That's what our doctors told us. If you were to slice us open from the front our organs would be lined up to mirror each other.'
Erin's heart is shifted slightly to the opposite side of her chest where as Ashley's heart sits in the usual place.
Childhood: The twins, who are 23, share opposite facial features. The right side of Erin's (above right) face is the same as the left side of Ashley's (above left). The pair are pictured above at an unknown age
Inseparable: The sisters, pictured above, even has mirrored cross-bites before they each got braces
Erin also detailed the exterior differences between her and her sister including how the right side of her face is identical to the left side of Ashley's.
SEEING DOUBLE: HOW ARE 'MIRROR IMAGE' TWINS CREATED
'Mirror image' twins are a result of the delayed split of a blastocyst, which is the name given to a group of cells that produce an embryo in a woman's body.
Once a single sperm fertilises a single egg, a group of cells known as the blastocyst is formed.
When the blastocyst splits, two embryos are produced, thus creating twins.
If the blastocyst splits into two separate parts in the first 9-12 days, identical twins will be born.
But if there is a delay in the split, the twins become mirror images of one another and develop asymmetric features.
She wrote: 'If she [Ashley] sits across from me and is eating or writing with her left hand I will look like her mirror image eating with my right. In a sense, if we stood in front of each other we would be the other's reflection.'
Erin is also left-handed while Ashley is right-handed.
She wrote: 'We have mirrored cross-bites too… or we did before the braces.'
Their personalities also differ; Erin wrote that she loves 'being the silent one' of the two.
She continued: 'Ash is very very VERY outgoing. She was the talker and I was the listener. Even to this day she will dominate a conversation and I will just as happily listen. I like to just sit quietly and write.'
Physically, they were hard to tell apart as young children.
Erin said that their parents used their 'skin markings' in order to differentiate the twins.
'We do not have mirrored moles and such,' Erin said. 'That's how mom and dad would tell us apart when we were little. I have a mole on my chest and on my middle finger.
Love: Ashley, above in a photo that Erin took of her, is very protected by her sister. The pair are close-knit
Close: While the twins have very different personalities – one is 'very VERY outgoing' while the other is quiet and prefers to write – they are close friends. Erin, below, wrote that they 'always lie like this'
'Now that I'm grown up, you can't exactly look at the one on my chest to determine who I am without being indecent. Middle finger = the next best thing.'
The two are extremely close-knit but Erin has proved something of a protector over her twin.
She wrote: 'I would probably be considered the 'evil' one from her past boyfriends. I am very VERY protective of Ash. If someone hurts her I would lash out at them with the fury of ten mothers.
Today: Erin, above, posted this image on Reddit after receiving a flood of questions about life as a twin
'I just about beat up one of her boyfriends that cheated on her, and I completely let another boy have it for spreading bad rumors about her at school. If you mess with her be prepared to feel my wrath.'
The twins also shared weight struggles.
Erin wrote: 'We were both heavy in middle grades. I then lost a lot of weight in 8th grade, which inspired her to do the same.'