NEET Botany Molecular Basis of Inheritance Questions Solved

NEET - 2013

Which enzymes/s will be produced in a cell in which there is a non-sense mutation in the lac Y gene?

(1) β-galactosidase

(2) Lactose permease

(3) Transacetylase

(4) Lactose permease and transacetylase

(1) β -galactosidase is a structural gene present in segment of DNA, which carry codes for the synthesis of protein. Mutation in the lac Y gene of E. coil needs residues of cytoplasmic enzyme, β-galactosidase. Lactose permease is a membrane protein, which is a major facilitator superfamily. Transacetylase is an enzyme transferring acetyl groups from one compound to another.

The lac genes encoding enzymes are lac Z, lac Y, and lac A. Transcription of lac Z gene occurs before transcription of lac Y & lac A. A nonsense mutation in the lac Y gene will produce nonfunctional permease. A stop codon will be introduced in the sequence after lac Z gene. Since only
β-galactosidase enzyme is produced and permease and transacetylase enzymes are not produced, lactose is not transported into the cell.

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