1 gram of DNA is how much? Nice to give something a measurement of volume, but a reference point would have helped. Lets compare to a grain of sand.
Assuming an average weight of 68 milligrams / grain then it takes 15.4 grains of sand = 1 gram
DNA is very tiny, so tiny its weighed in Daltons. so lets do a grain of sand in Daltons.
One gain of sand weighs 3.9X10^22 Daltons (39,022,820,000,000,000,000,000) or 39 sextillion daltons.
One molecule of DNA weights about 1 million daltons
http://www.worldchanging.com/archives/002796.html
39 sextillion / 1 million is a much easier number only 39 quadrillion, or 39 million billions. Now lets make that even easier, instead of using 700 terabytes, lets use bytes instead. Divide that number by 700 trillion and you are down to a respectable 55.7 bytes.
Now multiple by 15.4 (grains of sand / gram) so we can extrapolate our final results.
The original article writers could have easily stated this is simple terms instead of using a grossly over scale measurement such as a gram.
A single strand of DNA holds roughly 850 bytes of data.