Chapter 13, Problem 1TYU

Summary Introduction

Introduction: A gene is a set of nucleotides that code for a particular protein. Gene expression causes the synthesis of a protein. The gene expression is regulated in controlled way depending on the requirement of the cell. For example, proteins involved in cell division are synthesized prior to the cell division. Prokaryotic and eukaryotic genes have differential gene expression in order to suit the specific needs of the cell.

Answer to Problem 1TYU

Correct answer: Beadle and Tatum studied the relationship between genes and enzymes in Neurospora. Hence, the correct answer is option (e).

Explanation of Solution

Reason for the correct answer.

Option (e) is given as “studied the relationship between genes and enzymes in Neurospora”.

Beadle and Tatum took thousands of haploid wild-type Neurospora and exposed their spores to X-rays or ultraviolet radiation to produce mutant strains. Then, the mutant strain is tested and identified that the actual enzymatic step is blocked due to the mutant gene that prevents the production of chemical which is essential for growth. The experiment of Neurospora exposed that each mutant strain had a particular mutation in only one gene and the gene mainly affects one enzyme-catalyzed chemical reaction. Beadle and Tatum proposed one gene-one enzyme hypothesis and this explains the one-to-one correspondence between genes and enzymes.

Hence, the correct answer is option (e).

Reasons for incorrect answers.

Option (a) is given as, “predicted that tRNA molecules would have anticodons”. At the time of Beadle and Tatum experiment, the hypothesis about tRNA is not given. Hence, option (a) is incorrect.

Option (b) is given as, “discovered the genetic disease alkaptonuria”. Physician and biochemist Archibald Garrod discovered the genetic disease alkaptonuria. Hence, option (b) is incorrect.

Option (c) is given as, “showed that the genetic disease sickle cell anemia is caused by a change in a single amino acid in a hemoglobin polypeptide chain”. Linus Pauling, a chemist in United States (U.S.) showed that the genetic disease sickle cell anemia is caused by a change in a single amino acid in a hemoglobin polypeptide chain. Hence, option (c) is incorrect.

Option (d) is given as, “worked out the genetic code”. Beadle and Tatum is not associated with the experiment of genetic coding. Hence, option (d) is incorrect.

Hence, the options (a), (b), (c), and (d) are incorrect.

Conclusion

In the early 1940s, a new approach is developed about understanding the relationship between genes and enzymes in Neurospora by the experiment of U.S. geneticists George Beadle, Edward Tatum, and their associates.