D) The Earth was hit by a one or more objects from space 65 million years ago. The iridium layer shows an extraterrestrial cause for the extinction at the Cretaceous Tertiary boundary, discovered by the Alvarez family. The first discovery of this layer was in the Bavarian alps, in Lattengebirge. The Alverez family proposed that the extinction of the dinosaurs was due to a large meteor hitting the Earth at the end of the Cretaceous period, marking the KT boundary with this clay layer which has a high content of iridium. Iridium is not common on Earth, but is common in meteors.
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Reverse transcriptase use mRNA to
form DNA apex
Reverse transcriptase is a broad
family of enzymes that play a unique role in the flow of genetic information. The
synthesis of DNA from an RNA template through reverse transcription produces
complementary DNA. Reverse transcriptase use an RNA template and a short
primer complementary to the 3' end of the RNA to direct the synthesis of the
first strand complementary DNA, which can be used directly as a template for
the Polymerase Chain Reaction.
