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
- 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
- Biology
- Molecular Basis of Inheritance
- 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
- Biology
- Molecular Basis of Inheritance
Construct and label a transcription unit from which the RNA segment given below has been transcribed. Write the complete name of the enzyme that transcribed this RNA.
- CBSE CLASS XII - 2025
- Biology
- Molecular Basis of Inheritance
- The base sequence in one of the strands of DNA is: ‘TAGCATGAT’
- Give the base sequence of its complementary strand.
- How are these base pairs held together in DNA molecule?
- Explain the base complementarity rule. Name the scientist who framed this rule.
- CBSE CLASS XII - 2025
- Biology
- Molecular Basis of Inheritance
Student to attempt either option-(A) or (B):
(A) Write the features a molecule should have to act as a genetic material. In the light of the above features, evaluate and justify the suitability of the molecule that is preferred as an ideal genetic material.
OR
(B) Differentiate between the following:- [(i)] Polygenic Inheritance and Pleiotropy
- [(ii)] Dominance, Codominance and Incomplete dominance
- CBSE CLASS XII - 2025
- Biology
- Molecular Basis of Inheritance
Questions Asked in NEET exam
A sphere of radius R is cut from a larger solid sphere of radius 2R as shown in the figure. The ratio of the moment of inertia of the smaller sphere to that of the rest part of the sphere about the Y-axis is :
- NEET (UG) - 2025
- Moment Of Inertia
Predict the major product $ P $ in the following sequence of reactions:
(i) HBr, benzoyl peroxide
(ii) KCN
(iii) Na(Hg), $C_{2}H_{5}OH$- NEET (UG) - 2025
- Organic Chemistry
AB is a part of an electrical circuit (see figure). The potential difference \(V_A - V_B\), at the instant when current \(i = 2\) A and is increasing at a rate of 1 amp/second is:
- NEET (UG) - 2025
- Electromagnetic Induction and Inductance
- A wire of resistance \(R\) is cut into 8 equal pieces. From these pieces, two equivalent resistances are made by adding four of these together in parallel. Then these two are added in series. The net effective resistance of the combination is:
- NEET (UG) - 2025
- Resistance
- Consider the diameter of a spherical object being measured with the help of a Vernier Callipers. Suppose its 10 Vernier Scale Divisions (V.S.D.) are equal to its 9 Main Scale Divisions (M.S.D.). The least count in the M.S. is 0.1 cm and the zero of V.S. is at -0.1 cm when the jaws of Vernier callipers are closed. If the main scale reading for the diameter is \(M = 5\) cm and the number of coinciding vernier division is 8, the measured diameter after zero error correction, is:
- NEET (UG) - 2025
- Measurement of length
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.
