Genotype Arabinose absent Arabinose present 2. CA 3. C A/C A 4. CAICA /gene are
ID: 204383 • Letter: G
Question
Genotype Arabinose absent Arabinose present 2. CA 3. C A/C A 4. CAICA /gene are frans in their gene are cis in their effects, For lower) in Figure 16.8 is pur reasoning. equences A, B, C, genes or regulatory and 2. Mutations in he following effects, that the enzyme is indicates that the a. On the basis of these results, is the C sequence an operator or a regulator gene? Explain your reasoning Do these experiments suggest that the arabinose operon is negatively or positively controlled? Explain your reasoning . Vhat type of mutation is c? In E. coli, three structural genes (A, D, and ) encode A enzymes A, D, and E, respectively. Sequence Ois an his operator. The sequences are in the order 0 A-DHE on mmm present * 2 Enzyme i Enzyme 2Explanation / Answer
Ans a. C is a regulator Gene.
In case of genotype A both are wild type so the enzyme is produced in the presence of arabinose. In B, where C is mutated enzyme is not produced even in the presence of arabinose. But if you consider C, if it is an operator arabinose should not be produced in any way. Here, C- A+ genotype in C (same as genotype B) whic is not able to peoduce arabinose isomerase is complmented by C+ A- genotype and able to prodce enzyme suggesting it is a postive regulator. If the mutation is in operator, it should be cis dominant and so can't be complmented or reversed.
Ans B. It is a positive regulator.
Consider the mutation is in negative regulator. In genotype A, when regulator is expressed it should block the expression of enzyme in the presence or absence of arabinose. In case of genotype B, it should be definitely produced where C is mutated. But it is not the case. In B where C is mutated enzyme is not produced meaning it is a positive regulator.
And C. Mutation is dominant and trans acting mutation.
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