Feeds

Geneticists report 'semi-identical' twins

Egg and sperm three-way

Security for virtualized datacentres

Geneticists in the US have discovered a previously unknown kind of twins they have called semi-identical. The twins are identical on their mother's side, but only share half of their father's DNA.

The discovery, which has been published in the journal Nature, has prompted some to suggest that the current classification system for twins is too simple and needs to be revisited.

The twins are technically chimeras: that is, their cells are not genetically uniform. Some cells contain male cells with an X and Y chromosome, others have female cells bearing a double load of Xs. In the journal Human Genetics, the researchers report that the proportion of XY and XX cells varies depending on the kind of tissue being examined.

For the genes to be distributed in this way, two sperm cells must have fertilised a single egg. Some DNA from each sperm is present in each child.

The sequence of events needed for the children to have been born is extremely unlikely: some scientists suggest the pair may be unique.

First, two sperm must fertilise a single egg. This does happen in about one percent of human conceptions. More often than not the fertilised egg does not form a viable embryo. This embryo must then split to form twins, who if they are to be identified as semi-identical, must subsequently come to the attention of scientists.

In this case, one of the twins was born with "ambiguous" genitalia, which brought in the scientists. They discovered that the baby is a true hermaphrodite, with both testicular and ovarian tissue, while the other twin is anatomically male.

Both children, now toddlers, are reportedly growing normally and have no mental developmental abnormalities.

According to Nature.com, in 2003 biologist Michael Golubovsky predicted that this kind of intermediate twin could result from "double fertilisation". He told the news service: There are a lot of unclear situations in the genetics of twins and twinning. We need to keep our eyes open for other unusual scenarios." ®

Security for virtualized datacentres

More from The Register

next story
Boffins who stare at goats: I do believe they’re SHRINKING
Alpine chamois being squashed by global warming
What's that STINK? Rosetta probe shoves nose under comet's tail
Rotten eggs, horse dung and almonds – yuck
Comet Siding Spring revealed as flying molehill
Hiding from this space pimple isn't going to do humanity's reputation any good
Kip Thorne explains how he created the black hole for Interstellar
Movie special effects project spawns academic papers on gravitational lensing
Experts brand LOHAN's squeaky-clean box
Phytosanitary treatment renders Vulture 2 crate fit for export
LONG ARM of the SAUR: Brachially gifted dino bone conundrum solved
Deinocheirus mirificus was a bit of a knuckle dragger
Moment of truth for LOHAN's servos: Our US allies are poised for final test flight
Will Vulture 2 freeze at altitude? Edge Research Lab to find out
prev story

Whitepapers

Why cloud backup?
Combining the latest advancements in disk-based backup with secure, integrated, cloud technologies offer organizations fast and assured recovery of their critical enterprise data.
A strategic approach to identity relationship management
ForgeRock commissioned Forrester to evaluate companies’ IAM practices and requirements when it comes to customer-facing scenarios versus employee-facing ones.
Security for virtualized datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
New hybrid storage solutions
Tackling data challenges through emerging hybrid storage solutions that enable optimum database performance whilst managing costs and increasingly large data stores.