When a solution of cesium chloride (CsCl) is subjected to high-speed centrifugation, a stable density gradient is formed. Meselson and Stahl found that when cell contents were subjected to centrifugation with a CsCl solution, a band of DNA formed at the CsCl density that matched the density of the DNA. This technique is called density-gradient centrifugation. The test tubes below show the results of density-gradient centrifugation of five different DNA samples. Assign letters a-e to the pictures above. A) DNA from E. coli cells grown in ^5N B) DNA from E. coli cells grown in ^14 N C) A 1: 1 mixture of DNA from cells grown in 14^N and cells grown in ^15 N D) A 1: 1 mixture of DNA from cells grown in 14^N and 15^N, heated (to disrupt hydrogen bonds) and cooled (to allow reannealing) E) DNA containing one strand of ^15 N-DNA and one strand of ^14 N-DNA

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Schools are being forced to embrace computers. unlike their "digital immigrant" teachers, these students are "digital natives", born into a world where technology is an integral part of everyday life. almost every student has access to a multitude of computers, laptops and tablet devices. it would be crazy to assume an assignment would  notbe written on computer in this day and age.many schools now have a 1-to-1 computer policy, and many districts and states in the united states have mandated computers or ipads across the state for every student,  including los angeles, the second largest school district in the country.but the thing is, when they tried it in la, it wasn't the success they hoped for. that's because the tablets weren't used as much as they expected. rather, it appeared there was a gap between the digital native's love of technology and their use of it in the classroom.this conflicted relationship with computers is also underscored by much of the literature on education. it is also highlighted in professional development and conferences such as  edutech.