Q.75 Select the technique most appropriate to demonstrate that lactose induces
the synthesis of β-galactosidase enzyme.
Options:
- (A) Northern Blot
- (B) Western Blot
- (C) Quantitative PCR
- (D) Southern Blot
Western Blot is the most appropriate technique to demonstrate that lactose induces β-galactosidase enzyme synthesis, as it directly detects the protein product. This makes option (B) correct for GATE Life Sciences exam preparation.
Option Analysis
(A) Northern Blot
Northern Blot detects specific RNA sequences by separating RNA via gel electrophoresis, transferring to a membrane, and hybridizing with DNA probes. It shows mRNA levels but cannot confirm functional protein synthesis from lactose induction.
(B) Western Blot
Western Blot identifies specific proteins using SDS-PAGE separation, membrane transfer, and antibody detection. Comparing β-galactosidase levels with/without lactose directly proves enzyme synthesis induction.
(C) Quantitative PCR
qPCR measures DNA amplification to quantify mRNA levels via reverse transcription. It assesses transcription but not translation into functional β-galactosidase protein.
(D) Southern Blot
Southern Blot detects DNA sequences through gel electrophoresis, blotting, and hybridization. It analyzes gene structure, not inducible enzyme expression.
Lactose Induces β-Galactosidase Synthesis Mechanism
Lactose induces β-galactosidase synthesis in the lac operon model, where enzyme protein levels must be measured directly. Western Blot is the gold standard technique for this demonstration in molecular biology experiments.
Why Western Blot Over Other Techniques?
Western Blot uses antibodies to quantify β-galactosidase protein after lactose treatment, confirming translation from induced mRNA. Northern Blot shows only RNA, qPCR measures transcripts, and Southern Blot ignores expression entirely.
Technique Detects Suitable for Lactose Induction? Why/Why Not Northern Blot RNA No Transcription only Western Blot Protein Yes Direct enzyme detection Quantitative PCR cDNA/RNA No No protein confirmation Southern Blot DNA No Gene structure only
