Problem 70 - Objective Biology for NEET

Question

Dikaryon and dikaryophase is seen in the case of (a) Ascomycetes (b) Basidiomycetes (c) Phycomycetes (d) Both (a) and (b)

Step-by-Step Solution

Answer

The correct option is (d) Both a and b.

Step 1 - Understanding the terms

Dikaryon and Dikaryophase represent a phase in the life cycle of certain fungi where two genetically different nuclei coexist within the same hypha. This is a characteristic of a certain group of fungi.

Step 2 - Matching the options

Ascomycetes and Basidiomycetes are the two groups of fungi where dikaryon and dikaryophase occur in their life cycle.

Step 3 - Making conclusion

Comparing our finding in Step 2 with the given options, we can say that dikaryon and dikaryophase is seen in both Ascomycetes and Basidiomycetes. So, the correct answer is both (a) and (b), which is option (d).

Key Concepts

Dikaryon

In the world of fungi, the term "Dikaryon" refers to a unique phase in their life cycle. Unlike most organisms, which house a single nucleus per cell, dikaryotic cells have two separate nuclei. These nuclei result from the fusion of two different mating types. This process is not the same as sexual reproduction in animals, but it serves a similar purpose—bringing together genetic material from two parents.

A dikaryotic phase is denoted by the presence of two genetically distinct nuclei within one cell and is crucial in the reproductive stages of certain fungi. This phase can persist for varying durations, depending on the species, before eventually leading to the formation of spores, where nuclei fuse and recombine genetically. Here are key points:

• The dikaryotic stage is a transient but essential period in the fungal life cycle.
• It allows for genetic variation and adaptation through recombination.
• Fungi remain in this state until conditions are favorable for further reproduction.

Understanding the dikaryotic stage gives us insight into the complex and fascinating life cycles of some fungi.

Ascomycetes

Ascomycetes, commonly known as sac fungi, are one of the largest groups of fungi on Earth. They are characterized by the formation of an ascus, a sac-like structure where spores are produced. These fungi exhibit a wide range of lifestyles, from decomposers to parasites to symbiotic relationships with plants.

The dikaryotic phase in Ascomycetes occurs between plasmogamy—the fusion of cytoplasm between two mating cells—and karyogamy—the fusion of nuclei. After plasmogamy, the two nuclei remain distinct in a dikaryotic state until they fuse within the ascus. This fusion eventually leads to the formation of asci containing spores.

Ascomycetes play a significant role in ecosystems and human industry:

• They are crucial decomposers, breaking down complex organic materials and recycling nutrients.
• Many are used in food production, such as yeast in bread-making and in the fermentation of alcoholic beverages.
• Certain species are utilized in pharmaceuticals for producing antibiotics like penicillin.

Through the dikaryotic phase, Ascomycetes ensure genetic diversity and evolutionary success.

Basidiomycetes

Basidiomycetes are another major group of fungi, recognized for their role in decomposing wood and organic matter. They include many familiar fungi such as mushrooms, puffballs, and toadstools. In Basidiomycetes, the dikaryotic phase is a prominent part of their life cycle, often lasting for most of their life as they form extensive networks of mycelium in soil or organic material.

The dikaryotic state in Basidiomycetes arises from the fusion of two compatible hyphae. This stage can be prolonged, creating a large dikaryotic mycelium, which eventually forms fruiting bodies such as mushrooms. It is within these fruiting bodies that the nuclei fuse inside specialized cells called basidia, leading to spore formation.

Key roles of Basidiomycetes include:

• Playing a critical role in nutrient cycling and decomposition, particularly in forest ecosystems.
• Forming symbiotic relationships with plants, enhancing nutrient uptake.
• Having ecological importance in maintaining soil health and structure.

Basidiomycetes' prolonged dikaryotic phase allows them to adapt and thrive in various environments, contributing to their ecological dominance.