Young Brisbane twins, a young boy and a woman, have actually been identified as just the 2nd set of semi-identical, or sesquizygotic, twins in the world — and the first to be identified by medical professionals throughout pregnancy.
“It is likely the mother’s egg was fertilised simultaneously by two of the father’s sperm before dividing,” stated Teacher Fisk, who led the fetal medication group that took care of the mom and twins while based at Royal Brisbane and Women’s Health center in 2014. Teacher Fisk, a previous President of the International Fetal Medication and Surgical treatment Society, worked along with Dr Gabbett.
“The mother’s ultrasound at six weeks showed a single placenta and positioning of amniotic sacs that indicated she was expecting identical twins. However, an ultrasound at 14 weeks showed the twins were male and female, which is not possible for identical twins.”
Similar twins result when cells from a single egg fertilised by a single sperm divide into 2, so similar twins are the exact same gender and share similar DNA. Fraternal twins take place when each twin establishes from a different egg and the egg is fertilised by its own sperm.
Dr Gabbett stated if one egg is fertilised by 2 sperm it results in 3 sets of chromosomes, one from the mom and 2 from the dad.
“Three sets of chromosomes are typically incompatible with life and embryos do not usually survive,” he stated.
“When it comes to the Brisbane sesquizygotic twins, the fertilised egg appears to have actually similarly divided up the 3 sets of chromosomes into groups of cells which then divided into 2, developing the twins.
“Some of the cells contain the chromosomes from the first sperm while the remaining cells contain chromosomes from the second sperm, resulting in the twins sharing only a proportion rather 100 per cent of the same paternal DNA.”
Sesquizygotic twins were first reported in the United States in 2007. Those twins pertained to medical professionals’ attention in infancy after one was identified with unclear genitalia. On examination of combined chromosomes, medical professionals discovered the young boy and woman equaled on their mom’s side however shared around half of their paternal DNA.
Teacher Fisk stated an analysis of around the world twin databases indicated simply how unusual sesquizygotic twins are.
“We at first questioned whether there were perhaps other cases which had been wrongly classified or not reported, so examined genetic data from 968 fraternal twins and their parents,” he stated.
“Nevertheless we discovered no other sesquizygotic twins in these information, nor any case of semi-identical twins in big worldwide twin research studies.
“We know this is an exceptional case of semi-identical twins. While doctors may keep this in mind in apparently identical twins, its rarity means there is no case for routine genetic testing.”
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