Respuesta :
Answer:
In the yeast signal transduction pathway, after both types of mating cells have released the mating factors and the factors have bound to specific receptors on the correct cells:
a. binding induces changes in the cells that lead to cell fusion.
Explanation:
There have been several studies about yeast cells and how they respond to the mating factors, a-factor and α-factor:
option b: the cells then produce the a factor and the factor, is not correct as they are mating factors.
These studies have greatly contributed to help understanding the way signals are transduced from a cell-surface receptor into a cell.
When yeast a cells are exposed to α-factor, they exhibit three responses, which are initiated in the moment the mating factor (a signaling molecule that acts between organisms, hence called a “pheromone”) binds to the receptor:
(1) they arrest in the G1 phase of the cell cycle, not option c: one cell nucleus binds the mating factors and produces a new nucleus in the opposite cell.
(2) they synthesize a variety of proteins involved in cell fusion, not option e: a growth factor is secreted that stimulates mitosis in both cells.
(3) they grow towards their mating partner, not option d: the cell membranes fall apart, releasing the mating factors that lead to new yeast cells.
The activated receptor triggers a so-called “MAP kinase cascade" protein kinase, followed by a transcriptional activator protein, Ste12. Ste12 inducing synthesis of assorted proteins that play an important role in arresting the cell cycle (the Far1 protein) and for cell fusion (the Fus1 protein).
