Question

How does yeast reproduce asexually? Show it diagrammatically.

Answer 1

Hint:Saccharomyces cerevisiae is an organism that has been used successfully for various kinds of research. Its process of asexual propagation is by budding under favourable conditions of nutrition and moisture, and temperature.

Complete answer:
In the process of budding, there are several stages. Initially, the parent cell starts to develop a small outgrowth, and simultaneously the yeast nucleus starts to divide by forming a constriction. As the bud increases in size, and starts to form a cell membrane between the parent cell and the bud, one nucleus moves towards the bud, the cell is pinched off, and the daughter cell separates from the parent.

In some conditions, budding occurs so rapidly that the daughter cells remain attached to each successive parent cell and a long clump or chain of yeast cells is formed. This is known as a pseudo mycelium. The daughter cells are smaller in size than the parent cell. When conditions are unfavourable, then the yeast forms spores. Baker’s yeast, the main microorganism involved in bread production undergoes rapid division and budding on activation.

Yeast can also undergo sexual reproduction in which two yeast cells come together, and form a conjugation tube, within which a number of ascospores are visible.

Note:In yeasts that divide by fission, the nucleus undergoes division in the centre of the parent cell, a cell partition is laid down in the middle of the cell, and two daughter cells of the same size are formed. These can separate and repeat the process. Fission is less common than budding.