In: Biology
Please correct if they are wrong
Genotype |
?-galactosidase |
Permease |
Outcome |
||
Lactose |
No lactose |
Lactose |
No lactose |
||
I+P+O+Z-Y-/ I+P+O+Z-Y- |
+ |
- |
+ |
- |
lac+ |
ISP+OCZ+Y-/ I+P-OCZ-Y+ |
- |
- |
- |
- |
lac- |
I+P+O+Z+/ I+P+O+Z+ |
+ |
- |
- |
- |
lac+ |
Lac operon is an inducible operon which means that the cistron undergoes transcription only when lactose is prsent in the medium. This is because the lac operon encodes for lactose-fermentation enzymes, hence presence of lactose in the cell/medium will prompt the cells to induce the operon. The lac operon contains a cistron carrying three genes. The lac Z encodes for beta galactosidase, lac Y encodes for permease and lac A encodes for transacetylase. All of these three genes need to be present and expressed for a successful lac operon transcription.
Thus, based upon these information, the answers can be found as below:
Case 1: No expression (the genotype is both negative for lacZ and Y, hence no transcription will take place)
Case 2: No expression (the expression of lac operon is absent in the absence of lactose in the medium)
Case 3: No expression (Since the lac Y gene is altogether absent from the cistron, no expression of cistron takes place)