We have linear DNA that is cut by the restriction enzymes EcoRI and Hpall, producing different fragment sizes. EcoRI cuts the DNA into three fragments of 0.4 kb, 1.7 kb, and 0.9 kb, indicating two restriction sites. Hpall cuts the DNA into two fragments, indicating one restriction site. When both enzymes cut the DNA, the fragments match what is expected based on the individual enzyme cuts, with Hpall cutting within the 1.7 kb EcoRI fragment.

1. We have linearDNA sowhenEcoRI cutsit makes3 fragmentssoithas 2 restrictionsitesandHpall is
making2 fragmentsso ithas onlyone restrictionsite.
WithEcoRI, we needto have fragmentsof 0.4 kb 1.7kb, and 0.9kb so we putthe tworestriction sites
makingthose fragments.
For one secondwe leave the Hpall onthe side andwe see the fragmentsthatwe have whenbothof
themare cutting.We can see that the two fragmentsof 0.9kb and0.4kb are alreadymade fromEcoRI so
we will notcut inthose fragments.Butwe alsoneedtwofragmentsof 1.2kb and 0.5kb and if we sum up
those twofragmentstheyare making1.7kb that isthe fragmentthatwe alreadyhave fromEcoRI,sowe
understandthatHpall will cutinthisfragment.