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 :
- in the presence of glucose, E. coli cells do not utilize lactose
- they cannot transport lactose from the medium into the cell
- the lac operon is constitutively active in these cells
- they cannot synthesize functional \(\beta\)-galactosidase
The Correct Option is D
Solution and Explanation
The Z gene of the lac operon encodes β-galactosidase, which is the enzyme responsible for breaking down lactose into its constituent sugars, glucose, and galactose. If the Z gene is mutated and cannot produce functional β-galactosidase, E. coli cells will be unable to metabolize lactose, and therefore, they cannot grow using lactose as the sole source of energy.
So, the correct option is (D): they cannot synthesize functional \(\beta\)-galactosidase
Top Questions on Molecular Basis of Inheritance
- Distance between two consecutive base pairs of DNA is \rule{2cm}{0.1mm}
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- Study the items of Column-I and those of Column-II:
Column-I Column-II
(a) RNA polymerase I (i) 18s rRNA
(b) RNA polymerase II (ii) SnRNAs
(c) RNA polymerase III (iii) hnRNA
Choose the option that correctly matches the items of Column-I with those of Column-II:- CBSE CLASS XII - 2025
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- The RNA triplet UAG acts as a stop codon which terminates the synthesis of a polypeptide. Below is given a strand of DNA which codes for four amino acids.
In which position will an insertion of a thymine nucleotide result in the termination of translation?
DNA strand:
3′ T C C A C C C G A T G C 5′- CBSE CLASS XII - 2025
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A full wave rectifier circuit with diodes (\(D_1\)) and (\(D_2\)) is shown in the figure. If input supply voltage \(V_{in} = 220 \sin(100 \pi t)\) volt, then at \(t = 15\) msec:
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Concepts Used:
Regulation of Gene Expression
The process by which the instructions present in our DNA are converted into a functional product, such as a protein is called Gene Expression. It is a tightly coordinated process that allows a cell to respond to its changing environment.
In the meanwhile process, genetic codes from the DNA code are converted into a protein with the help of translation and transcription. The genetic expression shows the process of the genetic makeup of an organism as its physical traits. All over the process, the information flows from genes to proteins.
For a better understanding, let us take the example of the Keratin genes. Keratin is a protein that helps in the formation of our hairs, nails, and skin. Usually, these things grow at a continuous speed as our hairs, nails, and skin get worn down over a period of time. The production of excessive keratin could form many hairs on the skin, dry and hard skin, and thick and long nails. To avoid this, it is necessary to regulate the expression of the keratin gene.
Regulation of gene expression includes different mechanisms through which our cells manage the amount of produced protein by our genes.
