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Spare parts.

[ILLUSTRATION OMITTED]

These 15 fingers and 16 toes belong to a 6-year-old boy. Experts say he probably has more digits than any other person. The boy recently underwent a 6.5-hour operation in China so doctors could remove the 11 spare parts. The boy's remaining 10 fingers and 10 toes work normally.

"The doctors had to take out all of the extra tendons and bones, and basically cut out a whole wedge of his hand," says Henk Roelink, a developmental biologist at the University of California, Berkeley.

About one in every 500 people is born with a spare finger or toe. You can also find extra digits on animals such as dogs, chickens, mice, and cats. Roelink has a cat, named Six, who has six digits on each paw. This painless condition is called polydactyly, which is Greek for "many fingers."

Additional appendages result from hereditary information that offspring inherit from their parents. The genes that cause too many fingers and toes are often recessive. Parents with one copy of the gene will have the usual number of digits. But offspring who inherit a copy of the gene from each parent will have too many.

Malfunctioning genes can also make too few body parts. This condition, called oligodactyly, Greek for "few fingers," is less common than polydactyly and cannot be repaired with surgery--though people with fewer fingers tend to lead normal lives.

"It's surprising how complex it is to make 10 digits," Roelink says. "Dozens of different molecules collaborate to make the right number of fingers and toes, but it almost always works," he adds.

Although there's nothing life-threatening about having too many or too few digits, the same genes can be lethal if triggered in organs like the heart or brain.

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Title Annotation:GROSS OUT!
Author:Binns, Corey
Publication:Science World
Article Type:Brief article
Geographic Code:1USA
Date:Apr 4, 2011
Words:292
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