Wild-type Neurospora crassais auxotrophic with respect to the vitamin __________, which therefore must be supplied by its environment. histidine arginine riboflavin ribonucleic acids biotin
The correct answer and explanation is:
Correct Answer: biotin
Explanation (300 words):
Neurospora crassa is a type of red bread mold that has been a model organism in genetics and molecular biology, particularly for studying gene function and metabolic pathways. A strain is considered wild-type if it represents the typical form found in nature, possessing the standard genetic makeup without mutations.
Interestingly, even the wild-type strain of Neurospora crassa displays auxotrophy for biotin. Auxotrophy means the organism cannot synthesize a specific compound essential for its growth and must obtain it from the environment. So, although it is considered “wild-type,” N. crassa still cannot produce biotin on its own and requires it to be present in its growth medium.
Why biotin?
Biotin is a B-vitamin (also known as vitamin B7 or vitamin H) that plays a crucial role as a coenzyme in various metabolic reactions, particularly in carboxylation reactions involving fatty acid synthesis and amino acid metabolism. N. crassa lacks the full biochemical machinery necessary to synthesize biotin from scratch.
This dependency on biotin has made N. crassa very useful in early studies of metabolic pathways and genetic mutations. Researchers used it in experiments to determine how specific genes are responsible for individual enzymatic steps—pioneering the “one gene–one enzyme” hypothesis.
What about the other options?
- Histidine and arginine are amino acids. Mutant Neurospora strains can be auxotrophic for these, but not the wild-type.
- Riboflavin (vitamin B2) and ribonucleic acids (RNA) are also essential molecules, but wild-type N. crassa can typically synthesize them without external supplementation.
Summary:
The wild-type strain of Neurospora crassa is auxotrophic for biotin, which must be supplied by the environment for normal growth. This characteristic has been central to its use in genetics research.