Genetics and the One Gene Hypothesis

In 1941, George Beadle and Edward Tatum conducted groundbreaking experiments with Neurospora crassa to explore how genes control biochemical processes. They proposed the 'one gene-one enzyme' hypothesis, suggesting each gene codes for a single enzyme affecting a metabolic pathway. Their work demonstrated that gene mutations could prevent the production of essential molecules, impacting organism growth. This hypothesis evolved, revealing genes also code for non-enzymatic proteins and multiple polypeptides. Beadle and Tatum's research laid the foundation for modern genetics and molecular biology.

What was the primary understanding of genes in the early 20th century?

• Genes were known to code for non-enzymatic proteins.

• Genes were thought to be responsible for genetic mutations.

• Genes were understood to control visible traits and biochemical pathways.

• Genes were believed to be composed of DNA.

What was the main hypothesis proposed by Beadle and Tatum?

• Genes are responsible for the entire metabolic pathway.

• Each gene codes for multiple enzymes.

• Genes do not influence biochemical processes.

• Each gene codes for a single enzyme that controls a step in a metabolic pathway.

Why did Beadle and Tatum choose Neurospora crassa for their experiments?

• It is a complex organism with many genes.

• It is resistant to X-rays.

• It is prototrophic and can grow on minimal medium.

• It has a long life cycle.

What was the result when mutant strains were transferred to minimal medium?

• Mutants produced new enzymes.

• Some mutants could not grow due to lack of essential molecules.

• All mutants grew successfully.

• Mutants became resistant to X-rays.

Which vitamins were the mutant strains unable to produce?

• Vitamin B2, Vitamin B3, and Vitamin B5

• Vitamin B6, Vitamin B1, and Vitamin B10

• Vitamin A, Vitamin K, and Vitamin B12

• Vitamin C, Vitamin D, and Vitamin E

What was the main evidence supporting the 'one gene-one enzyme' hypothesis?

• Mutations caused the need for multiple molecules.

• Mutations caused the need for a single molecule.

• Mutations had no effect on the organism.

• Mutations improved the organism's growth.

Who challenged the method of selecting mutants and why?

• Edward Tatum, because he disagreed with the hypothesis.

• George Beadle, because he wanted to use a different organism.

• Norman Horowitz, because he thought it was too simplistic.

• Max Delbrück, because he believed it excluded complex mutants.

How did Norman Horowitz's work contribute to the hypothesis?

• He showed that most isolated mutants had single functions.

• He confirmed that most mutants had multiple functions.

• He disproved the 'one gene-one enzyme' hypothesis.

• He introduced a new method of genetic analysis.

What is one way the 'one gene-one enzyme' hypothesis has evolved?

• Genes only code for enzymes.

• Genes can code for non-enzymatic proteins and non-coding RNAs.

• Genes are responsible for all cellular functions.

• Genes are not involved in protein synthesis.

What did Beadle and Tatum do after their Nobel Prize-winning discovery?

• Beadle continued experimental science, while Tatum retired.

• Beadle studied corn, while Tatum investigated E. coli.

• They both stopped working in genetics.

• Both focused on human genetics.