A geneticist introduces a transgene into yeast cells and isolates five independent cell lines in which the transgene has integrated into random places in the yeast genome. In four of the lines, the transgene is expressed strongly, but in the fifth there is no expression at all. Which is a likely explanation for the lack of transgene expression in the fifth cell line?A) A transgene integrated into a heterochromatic region of the genome. B) A transgene intergrated into a euchromatic region of the genome. C) The transgene was mutated during the process of integration into the host cell genome D) The host cell lacks the enzymes necessary to express the transgene. E) A transgene integrated into a region of the genome characterized by high histone acetylation

This is most likely the reason why the transgene is not expressed in the fifth cell line. It is likely that the transgene was integrated into a heterochromatic region of the genome. Heterochromatin consists of genetically inactive satellite sequences, and many of these are repressed to various extents. Moreover, because this is a tightly packed form of DNA or condensed DNA, it is inaccesible to polymerases and thus not transcribed.