Why does dividing DNA length by restriction site length give fragments?

[LadiesMan]

A piece of linear DNA is 150 000 base pairs in length and it is digested with a restriction enzyme that recognizes a seven-base-pair recognition site. How many fragments do you predict would be produced? Show your calculations.

I would say, 150000bp / 7 = 21428.57 fragments (Weird...)

What am I doing wrong?

Thanks

 

[jim mcnamara]

A restriction enzyme cuts the DNA at the recognition site. Not every seven base pairs.

 

[LadiesMan]

Hmm, but we don't know how many restriction enzymes are on that linear piece of DNA.

 

[LadiesMan]

maybe:

4 nitrogenous pairs each base pair so 4^7 = 16384 (base pairs) then 150000 divide by 16384 which gives us 9.15 so approximately 9 fragments.