Download App

Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYMolecular Basis of Inheritance1 Mark
MCQ
For question, two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion: Regulator and operator genes are not associated with constitutive genes
Reason: Constitutive genes need not be repressed.
  • ✓
    Both assertion and reason are true, and reason is the correct explanation of assertion.
  • B
    Both assertion and reason are true, but reason is not the correct explanation of assertion.
  • C
    Assertion is true, but reason is false.
  • D
    Both assertion and reason are false
✓

Answer

Correct option: A.
Both assertion and reason are true, and reason is the correct explanation of assertion.
Regulator gene controls the operator gene in cooperation with a chemical compound called inducer present in the cytoplasm. The regulation gene codes for and produce a protein substance called repressor. The repressor substance combines with the operator gene to repress its function. Therefore it is called regulator gene. The constitutive genes keep on functioning all the time. They need not be repressed. Therefore, the regulator and operator genes are not associated with them.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "Assertion (A) & Reason (B) MCQ" from Molecular Basis of Inheritance→Molecular Basis of Inheritance — all question types→BIOLOGY STD 12 Science question papers→Maharashtra Board STD 12 Science question papers→Maharashtra Board question paper generator→

Similar questions

Directions : In the following questions, the Assertions $(A)$ and Reason $(s) \ (R)$ have been put forward. Read both the statements carefully and choose the correct alternative from the following:
Assertion : $\text{PCR}$ can detect very low amounts of $\text{DNA}$ and is now routinely used to defect $\text{HIV}$ in suspected $\text{AIDS}$ patient.
Reason : $\text{PCR}$ is a powerful technique to identify many other genetic disorders.
→
For question two statements are given $-$ one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion : Phytoplanktons grow in abundance in the profundal zone of lake.
Reason : Profundal zone is illuminated by light which supports growth of phytoplanktons.
→
For question two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion : Karyotypes study is used to detect of chromosomal aberrations.
Reason: Karyotypes can be used to know the sex of unborn child.
→
For question, two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion: Lactose in lac operon is promoter gene.
Reason: Lactose inactivates the repressor gene.
→
Two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion: Vitamins $B_2$ is found in cereals, green vegetables, brewer's yeast, egg white, milk and liver.
Reason: Vitamins $B_2$ can be commercially produced by some yeasts.
→
For question two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion : Linked gene show dihybrid ratio of $9 : 3 : 3 : 1.$
Reason: Linked gene undergo independent assortment.
→
How does silencing of specific mRNA in RNA interference prevent parasitic infestation?
→
For question two statements are given $-$ one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion : With increase in population size, environmental resistance tends to increase.
Reason : This is a nature's way to check the expression of biotic potential.
→
For question, two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion: Core enzyme catalyses chain elongation of $\text{RNA}.$
Reason: The presence of sigma factor is required for initiation of transcription.
→
For two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion: Placenta is tissue present inside the ovary.
Reason: Placenta bears ovules.
→