Download App

Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceBIOLOGYMolecular Basis of Inheritance1 Mark
Question
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.
  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false
Assertion: No lac mRNA is made in the presence of glucose.
Reason: In the presence of glucose and lactose activity of lac operon is not needed.
✓

Answer

  1. Both assertion and reason are true, and reason is the correct explanation of assertion.

Explanation:

The function of $\beta$ galactosidase enzyme in lactose metabolism is to form glucose by cleaving lactose. Thus if both glucose and lactose are present in the growth medium, activity of lac operon is not needed, and indeed, no $\beta$ galactosidase is formed until virtually all of the glucose in the culture medium is consumed. The lack of synthesis of $\beta$ galactosidase is a result of lack of synthesis of lac mRNA. No lac mRNA is made in the presence of glucose, because in addition of an inducer to inactivate the lac i repressor, another element (cAMP-CAP) is needed for initiating lac mRNA synthesis, the activity of this element is regulated by the concentration of glucose. However, the inhibitory effect of glucose on expression of lac operon is quite indirect.

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→Rajasthan Board STD 12 Science question papers→Rajasthan Board question paper generator→

Similar questions

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.
  1. Both assertion and reason are true and reason is the correct explanation of assertion.
  2. Both assertion and reason are true but reason is not the correct explanation of assertion.
  3. Assertion is true but reason is false.
  4. Both assertion and reason are false.
Assertion : Some diseases that attack in childhood do not attack again.
Reason: Memory cells plays an important role.
→
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.
  1. Both assertion and reason are true and reason is the correct explanation of assertion.
  2. Both assertion and reason are true but reason is not the correct explanation of assertion.
  3. Assertion is true but reason is false.
  4. Both assertion and reason are false.
Assertion: Immobilised yeasts cause less fermentation.
Reason: Brewer's yeast produces beer not wine.
→
Assertion (A): Decomposition process is slower if detritus is rich in lignin and cutin.
Reason (R): Decomposition is largely an oxygen requiring process.
→
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.
  1. Both assertion and reason are true and reason is the correct explanation of assertion.
  2. Both assertion and reason are true but reason is not the correct explanation of assertion.
  3. Assertion is true but reason is false.
  4. Both assertion and reason are false.
Assertion: The introduction of Nile perch in lake Victoria caused cichlids to become extinct.
Reason: Nile perch is an indigenous species of East Africa.
→
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.
  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
Assertion: Corpus luteum secretes the female hormone progesterone.
Reason: After ovulation, a ruptured follicle tums into yellowish solid mass of cells called corpus albicans.
→
Assertion (A): Primer pheromones bring about physiological changes in the receivers.
Reason (R): Releaser pheromones cause immediate change in the receivers.
→
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.
  1. Both assertion and reason are true and reason is the correct explanation of assertion.
  2. Both assertion and reason are true but reason is not the correct explanation of assertion.
  3. Assertion is true but reason is false.
  4. Both assertion and reason are false.
Assertion: Mimicry is the resemblance of one organism to another.
Reason: Mimicry may be protective or aggressive.
→
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.
  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
Assertion: Double fertilization is unique to angiosperms.
Reason: Triple fusion occurs in both fertilization, i.e. first and second.
→
Some multinational companies patent biological sample of other country without permission is called as:
  1. Bioweapon
  2. Bioethics
  3. Biopiracy
  4. Biopatent
→
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.
  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
Assertion : A cholera patient is given glucose, electrolytes, and water.
Reason: These plasmolyse the disease causing germs.
→