Question

Explain briefly the life cycle of Neurospora crassa with neatly labelled diagram.

Answer 1

LIFE CYCLE OF NEUROSPORA CRASSA:

• The myelium of red bread mold, Neurospora crassa (an ascomycete fungus) is composed of intertwined, segmented filaments called hyphae.
• Each hyphal segment contains a haploid nucleus with seven chromosomes.
• N. crass reproduces asexually by haploid spores called conidia, and sexually by the contact of hyphae of two different mating types or strains, as A (+) and a (-) strains.
• The plasmogamy is followed by pairing of A or + nuclei in a single hyphal cell.
• Both contacting hyphae develop into a fruiting body called perithecium, in which many elongated sac-like sporangia called asel (singular ascus) are developed from diploid or A (+) and a (-) nuclei containing hyphae.
• Eventually, both nuclei of opposite strain unite forming a diploid zygote nucleus which soon undergoes meiosis to form four haploid melospores.
• Each meiospore then divides mitotically and thus, eight monoploid ascospores are formed.
• Four of these ascospores give rise to A or + mating strain, while the other four to a or-strain plant.
• The ascospores are liberated from the asci and germinate into new adults.

 

 

Neurospora crassa:

• This is a type of red bread mold of the phylum Ascomycota.
• The genus name, meaning "nerve spore"  refers to the characteristic striations on the spores. 
• This is used as a model organism because it is easy to grow and has a haploid life cycle which makes the genetic analysis simple as the  recessive traits will show up in the offspring.