Exams › NEET › Biology

E.coli cells with a mutated z gene of the lac operon cannot grow in medium containing only lactose as the source of energy because:

1. the lac operon is constitutively active in these cells
2. they cannot synthesize functional beta-galactosidase
3. in the presence of lactose E.coli cells do not utilize lactose
4. they cannot transport lactose from the medium into the cell

Correct answer: they cannot synthesize functional beta-galactosidase

Solution

The lacZ gene encodes beta-galactosidase, the enzyme that cleaves lactose into glucose and galactose. A mutated z gene means no functional beta-galactosidase, so the cells cannot use lactose as their sole energy source.

Related NEET Biology questions

• Which of the following is a transcription factor produced by a regulatory gene?
• Which of the following combination is false?
• Which scientist experimentally proved that DNA is the sole genetic material in bacteriophage?
• If the distance between two consecutive base pairs is 0.34 nm and the total number of base pairs of a DNA double helix in a typical mammalian cell is 6.6 × 10⁹ bp, then the length of the DNA is approximately
• Which of the following RNAs should be most abundant in animal cell?
• The final proof for DNA as the genetic material came from the experiments of:

⚔️ Practice NEET Biology free + battle 1v1 →