Fill in the Missing Blanks with Single Words

Essay

Fill in the missing blanks with single words.
In the recent past, virus vectors used in gene therapy trials were often based on a type of retrovirus called a ______1_______retrovirus. They had the advantage of allowing a _____2_____ DNA to be stably inserted into the _____3____ DNA of cells. For cells that are short-lived, such as blood cells, the hope was that a certain percentage of _____4_____ cells might be successfully transduced so that there was a self-renewing population of cells carrying the desired _____2_____ DNA. Unfortunately, vectors based on ______1_______retroviruses have a poor safety profile: there is little control over where they ______5_______ into the _____3____ DNA and sometimes when they _____5_____ they activate a neighboring _____6_____, causing _____7_____. As a result, in modern gene therapy trials it is now commonplace to use self-_____8______ strains of a class of retrovirus vectors known as _____9____ that are much safer to use.