Question

An auxotroph is
(a)Plant capable of synthesizing its own carbohydrates.
(b)Plant showing bending response to sunlight.
(c)A mutant having lost the ability to synthesize one or more nutrients.
(d)An organism dependent upon another for nutritional requirements.

Answer 1

Auxotrophs are wild type strains that are first grown on a supplemented medium, and then the colonies transferred to the minimal medium. Colonies that grow on supplemented, but not minimal media are selected as auxotroph.

Complete answer:
The original protoplasts have the capacity to grow in the minimal medium known as Prototroph. The mutants of the prototroph which do not have the capacity to grow in the minimal medium are known as Auxotroph. The hybrid protoplasts are known to grow in the minimal medium and parental protoplasts aren’t able to grow within the minimal medium. It helps in selection procedures.

Additional Information: Isolation of auxotroph:-
-By using certain blocked mutants, desired products such as amino acids and nucleotides may be formed via branching biosynthetic pathways.
-The isolation of auxotrophs is completed by plating of the mutagenized population on a complete agar medium, on which the biochemically deficient mutants can also grow.
-The antibiotic resistance character can not only be used as a genetic marker, but mutants isolated may also have increased cell permeability or protein synthesis, making them useful for industrial purposes.
-By the use of Lederberg’s well-known replica plating technique, the clones are transferred to a minimal medium where the auxotrophic colonies cannot grow. These mutants are picked up from the master plates and their defect is characterized.
-After mutagenesis, the spores of filamentous organisms (actinomycetes, fungi) are allowed to develop in a liquid minimal medium.
-The developing microcolonies of prototrophs are then separated by filtration, leaving behind in the filtrate spores of auxotrophs, which have been unable to grow. The filtrate is then plated and therefore the resulting colonies are checked for auxotrophic characteristics.

So, the correct answer is ‘A mutant having lost the ability to synthesize one or more nutrients.’

Note: Molecular Screening of mutant species
-Targeted mutations require screening to detect individuals with the desired mutation. Techniques are almost like for human disease and DNA typing and use PCR, restriction enzyme analysis and DNA probing.
-An example is yeast genome analysis, which attempts to systematically identify the approximately 6,000 ORFs in that organism by knocking out each one in turn and determining the phenotype.
-Knocked-out gene is replaced with a kanamycin resistance (kanR) gene. The knockout is confirmed by PCR.
-Size of PCR product with defined primers indicates whether substitution of kanR for the target DNA has been successful.