Download App

Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

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

Similar questions

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: Infundibulum is a funnel shaped part closer to ovary.
Reason: The edges of infundibulum helps in collection of the ovum after ovulation.
→
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: Chlamydia trachomatis is a human pathogen that causes trachoma, sexually transmitted and perinatal infection.
Reason: Chlamydia trachomatis has DEFGHIJK serotypes.
→
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: Seminiferous tubule is related with spermatogenesis.
Reason: Spermatogenesis takes place under the influence of pituitary gonadotrophins and testosterone
→
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 : Number of chromosomes in one genome is equal to number of linkage groups.
Reason: Two homologous chromosomes form a linkage group.
→
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 : Inflammatory response is produced in the body after some infections.
Reason: This is one type of defence mechanism.
→
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: Azolla is used as a biofertiliser in rice fields.
Reason: Azolla shows the presence of N2 - fixing bacteria in its leaf cavities.
→
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: The egg apparatus, consists of two synergids and one egg cell.
Reason: Filiform apparatus play an important role in guiding the pollen tubes into the synergids.
→
Assertion (A): The earliest organisms that appeared on the earth were non-green and presumably anaerobes.
Reason (R): The first autotrophic organisms were the chemo-autotrophs that never released oxygen.
→
Assertion (A): Reproductive health means total well-being in all aspects of reproduction, i.e., physical, emotional, behavioural, and social.
Reason (R): A society with people having physically and functionally normal reproductive organs might be called reproductively healthy.
→
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: Coral reefs are found in temperate forests.
Reason: Minimum diversity of biota are found in the reefs.
→