I would appreciate the help. Figure 16.2 RESEARCH QUESTION: What do genes do? HY
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Question
I would appreciate the help.
Figure 16.2 RESEARCH QUESTION: What do genes do? HYPOTHESIS Each gene contains the information required to make one enzyme. NULL HYPOTHESIS Genes do not have a one-to-one correspondence with enzymes EXPERIMENTAL STRATEGY Mutate specific genes. Test to see if each mutant also lacks one of the enzymes required for different steps the pathway for synthesizing arginine. EXPERIMENTAL SETUP Isolate mutant N. crassa that cannot synthesize arginine. Grow each type of mutant on normal medium that is The slanted surface provides adequate room for growth Neurospora crassa Supplemented with Supplemented Supplemented Growth Not supplemented with arginine only with ornithine only citrulline only medium (no ornithine, (no citrulline (no ornithine (no ornithine citrulline, or arginine) or citrulline) or arginine) or arginine PREDICTION: There will be three distinct types of mutants, corresponding to defects in enzyme 1, enzyme 2, and enzyme 3 in the pathway for synthesizing arginine. Each type of mutant will be able to grow on different combinations of the four types of media. PREDICTION OF NULL HYPOTHESIS: There w a simple correspondence between a particular mutation and a particular enzyme. RESULTS There are three distinct types of mutants, called arg1, arg2, and arg3, each defective in one enzyme. Supplement type ornithine only Citrulline only None Arginine only no growth GROWTH GROWTH OROWITH arg1 no growth no growth Mutant type arg2 GROWTH GROWTH no growth no growth GROWTH arg3 no growth INTERPRETATION Precursor Ornithine Citrulline Arginine arg2 cells lack arg1 cells lack arg3 cells lack enzyme 1 enzyme 2 enzyme 3 CONCLUSION: The one-gene, one-enzyme hypothesis is supported. 2014 Pearson Education, IncExplanation / Answer
Answer:
1. The above experiment demonstrates one-gene, one-enzyme hypothesis originally done by Beadle and Tatum.
George Beadle and Edward Tatum exposed bread mold to X-rays, creating mutants that were unable to survive on minimal medium as a result of inability to synthesize certain molecules. Using crosses, they identified three classes of arginine-deficient mutants, each lacking a different enzyme necessary for synthesizing arginine.
They developed a one gene-one enzyme hypothesis, which states that each gene dictates production of a specific enzyme
Conclusion of the mold experiment: specific genes are responsible for the production of specific enzymes.
2. Some potential questions that may be asked are:
a. Is the one gene-one enzyme hypothesis correct?
Answer: One gene-one enzyme hypothesis was wrong because some proteins aren't enzymes (examples: insulin, keratin, hemoglobin).
b. What alternative hypothesis can be suggested if the above hypothesis is not correct?
Answer: Many proteins are composed of several polypeptides, each of which has its own gene, so the hypothesis has can be restated as the one gene-polypeptide hypothesis. But, it is common to refer to gene products as proteins rather than polypeptide, even when they are merely subunits in a larger protein (example: hemoglobin).
c. What other molecules can be encoded by genes and what is a good definition for a gene today?
Answer: It can code for DNA.
Gene: A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).