Question

While working on Neurospora crassa, Beadle and Tatum proved that

• A. Every gene is responsible for a specific enzyme.
• B. Plant cells are totipotent.
• C. DNA replication is semiconservative.
• D. Viruses have genetic material.

Answer 1

Answer: (A)

Every gene is responsible for a specific enzyme.

George Beadle and Edward Tatum exposed spores of the fungus Neurospora crassa to X-rays and other agents which damage DNA and cause alterations in DNA sequence (mutations). They observed that mutant fungal strains which lacked one or another specific enzymes sometimes result in the failure of an entire metabolic pathway. It was concluded that a gene is a segment of genetic material that codes for one enzyme; the one gene–one enzyme hypothesis. The Meselson-Stahl experiment showed the semiconservative mechanism of DNA replication in which a DNA strand serves as a template for the synthesis of a new strand and produces two new DNA molecules, each with one new strand and one parental strand. Totipotency is the ability of plant cells to regenerate into embryo under favorable conditions. Viruses are obligate intracellular parasites, with acellular structure, can not independently fulfill the characteristics of life and are composed of protein shell (capsid) surrounding nucleic acid (ss or ds RNA or DNA). The correct option is A.