Download App

Human Health and Disease — BIOLOGY STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceBIOLOGYHuman Health and Disease1 Mark
MCQ
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 : Some diseases that attack in childhood do not attack again.
Reason: Memory cells plays an important role.
  • ✓
    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.
This can be explained in terms of memory cells. After the infection disappears as a result of antigen$-$antibody interaction and killer $T-$cell$-$nonself cell interaction, some of the specific lymphocytes remain in lymphatic tissue as "memory or primed cells" which are ready to produce the antibodies and killer cells if the same antigens reappear. That is why the second attack of the infectious disease elicits quick and abundant antibody formation. The memory cells can give rise to more effector cells and memory cells in case of a second attack of antigens. Whereas the effector cells have a life of a few days only. and the memory cells live long, some even for whole life. The memory cells are stored in the spleen and lymph nodes.

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 Human Health and Disease→Human Health and Disease — all question types→BIOLOGY STD 12 Science question papers→Gujarat Board STD 12 Science question papers→Gujarat 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.
Assertion : Constitutive genes are continuously being expressed.
Reason : Constitutive genes are frequently needed for various metabolic functions.
→
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: Quantitative inheritance is called polygenic inheritance.
Reason: Several genes control the expression of a trait.
→
Assertion (A): Large holes in Swiss cheese are due to the production of a large amount of carbon dioxide by specific microbe.
Reason (R): The specificity of characteristic texture, flavour and taste of Swiss cheese is due to the use of bacterium Propionibacterium shermanii.
→
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: Cilia lining the fallopian tube helps to pick up and push the released ovum into the oviduct.
Reason: Cilia of fallopian tubes beat towards uterus.
→
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 : $Y$ chromosome causes maleness.
Reason: If the number of $X$ chromosome is more than one, femaleness dominates.
→
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: Ectotherms are able to remain active under cold conditions.
Reason: Ectotherms are able to maintain a constant internal temperature, even when the temperature outside fluctuates.
→
Gene therapy has been successful in curing genetic diseases in laboratory animals through
→
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 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: Sequences of bases in one polynucleotide chain of $\text{DNA}$ can determine the sequence of bases in the other chain.
Reason: In a $\text{DNA},$ amount of adenine equals that of thymine and amount of guanine equals that of cytosine$, i.e., A = T$ and $C = G.$
→
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: Non$-$native or exotic species are often introduced in a region for their economic uses.
Reason: Exotic species are considered to be a major cause of extinction of indigenous species.
→