Feeds

Geneticists report 'semi-identical' twins

Egg and sperm three-way

Beginner's guide to SSL certificates

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." ®

Top 5 reasons to deploy VMware with Tegile

More from The Register

next story
Bond villains lament as Wicked Lasers withdraw death ray
Want to arm that shark? Better get in there quick
Antarctic ice THICKER than first feared – penguin-bot boffins
Robo-sub scans freezing waters, rocks warming models
Your PHONE is slowly KILLING YOU
Doctors find new Digitillnesses - 'text neck' and 'telepressure'
SEX BEAST SEALS may be egging each other on to ATTACK PENGUINS
Boffin: 'I think the behaviour is increasing in frequency'
Reuse the Force, Luke: SpaceX's Elon Musk reveals X-WING designs
And a floating carrier for recyclable rockets
The next big thing in medical science: POO TRANSPLANTS
Your brother's gonna die, kid, unless we can give him your, well ...
NASA launches new climate model at SC14
75 days of supercomputing later ...
Britain's HUMAN DNA-strewing Moon mission rakes in £200k
3 days, and Kickstarter moves lander 37% nearer takeoff
Renewable energy 'simply WON'T WORK': Top Google engineers
Windmills, solar, tidal - all a 'false hope', say Stanford PhDs
prev story

Whitepapers

Choosing cloud Backup services
Demystify how you can address your data protection needs in your small- to medium-sized business and select the best online backup service to meet your needs.
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.
Go beyond APM with real-time IT operations analytics
How IT operations teams can harness the wealth of wire data already flowing through their environment for real-time operational intelligence.
The total economic impact of Druva inSync
Examining the ROI enterprises may realize by implementing inSync, as they look to improve backup and recovery of endpoint data in a cost-effective manner.
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.