DNA restriction enzymes cut the DNA molecule, while DNA ligases join the resulting DNA fragments
Explanation:
Transformation is a naturally occurring process by which bacteria incorporate exogenous genetic material from their surrounding environment. This process (transformation) is used for DNA cloning via plasmid vectors. In DNA cloning, transformation occurs after restriction enzymes cut the DNA at specific sequences named palindromic sequences (i.e, sequences that can be read the same in opposite direction). Restriction enzymes can generate sticky-ends, where enzymes make staggered cuts in the two strands (e.g., <em>BamH</em>), or blunt ends, where the resulting strands are of the same length (e.g., <em>HaeIII</em>). In general, sticky-end enzymes are more useful because they generate a 3' overhang in one molecule and a complementary 5' overhang in the other, increasing the yield and specificity of ligation. During ligation, a DNA ligase is used to join both DNA strands by forming phosphodiester bonds in the plasmid. Following transformation, bacteria can be selected on antibiotic plates.
Magnetic reversal proves seafloor spreading because we can see the polarity of the Earth's magnetic field in rocks. As magma cools, particles in it get “frozen” in the direction of the magnetic field. ... The magnetic evidence shows that the oldest rocks are far away from the ridge and the newest rocks are closest.
Our water resources face a host of serious threats, all of which are caused primarily by human activity. They include sedimentation, pollution, climate change, deforestation, landscape changes, and urban growth.
