Look at the two yeast colonies in Figure Q4–3. Each of these colonies contains about 100,000 cells descended from a single yeast cell, originally somewhere in the middle of the clump. A white colony arises when the Ade2 gene is expressed from its normal chromosomal location. When the Ade2 gene is moved to a location near a telomere, it is packed into heterochromatin and inactivated in most cells, giving rise to colonies that are mostly red. In these largely red colonies, white sectors fan out from the middle of the colony. In both the red and white sectors, the Ade2 gene is still located near telomeres. Explain why white sectors have formed near the rim of the red colony. Based on the patterns observed, what can you conclude about the propagation of the transcriptional state of the Ade2 gene from mother to daughter cells in this experiment?

Figure Q4–3

Transcribed Image Text:

telomere telomere Ade2 gene at normal location white colony of yeast cells Ade2 gene moved near telomere red colony of yeast cells with white sectors