A geneticist introduces a transgene into yeast cells and isolates five independent cell lines in which the transgene has integrated into the yeast genome. In four of the lines, the transgene is expressed strongly, but in the fifth there is no expression at all.
-Which of the following 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 integrated 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.

Question

Quizplus · Accepted Answer

Heterochromatin is typically characterized by compacted chromatin structure with heavy methylation of histones and DNA. This can prevent access of the transcriptional machinery to genes within heterochromatic regions, leading to lack of expression. Therefore, it is likely that the transgene integrated into a heterochromatic region in the fifth cell line, leading to lack of expression.

A Geneticist Introduces a Transgene into Yeast Cells and Isolates