In most fungi, karyogamy does not immediately follow plasmogamy, which consequently:
A. means sexual reproduction can occur only in specialized structures.
B. results in a dikaryotic phase.
C. results in multiple diploid nuclei per cell.
D. allows fungi to reproduce asexually most of the time.
E. allows the formation of large, macroscopic fruiting bodies.
The correct answer and explanation is :
The correct answer is B. results in a dikaryotic phase.
Explanation:
In the sexual reproduction of fungi, two processes occur sequentially: plasmogamy and karyogamy.
- Plasmogamy is the fusion of the cytoplasm from two different fungal cells, but the nuclei from each cell remain separate. This creates a dikaryotic cell, which contains two distinct, haploid nuclei.
- Karyogamy, the fusion of these two haploid nuclei into a single diploid nucleus, occurs later in the process. However, in many fungi, there is a significant delay between plasmogamy and karyogamy, which leads to the dikaryotic phase. This phase is an essential characteristic of the life cycle of many fungi, particularly those in the division Basidiomycota (such as mushrooms) and Ascomycota (such as yeasts and molds).
The dikaryotic phase allows for the existence of cells that contain two different nuclei, which can then later fuse through karyogamy to form a diploid nucleus. This delay provides flexibility in the reproductive cycle, and these dikaryotic cells can continue to grow and divide until the right environmental conditions trigger the completion of the sexual reproductive cycle.
The dikaryotic phase is a defining feature of many fungi because it allows for genetic recombination and contributes to the diversity seen in fungal populations. Once karyogamy occurs, the diploid nucleus undergoes meiosis, producing haploid spores that will germinate and begin the cycle anew.
Why other options are incorrect:
- A. Sexual reproduction occurs in specialized structures: While sexual reproduction in fungi often happens in specialized structures, this is not directly related to the delay between plasmogamy and karyogamy.
- C. Results in multiple diploid nuclei per cell: This is incorrect because the dikaryotic phase involves two haploid nuclei, not diploid ones.
- D. Allows fungi to reproduce asexually most of the time: Asexual reproduction can occur in fungi, but it is not a result of the delay between plasmogamy and karyogamy.
- E. Allows the formation of large, macroscopic fruiting bodies: While the dikaryotic phase is necessary for the formation of fruiting bodies, it does not directly cause their formation; other factors are involved as well.