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Assertion : The heterocyclic compounds i...

Assertion : The heterocyclic compounds in nucleic acid are the nitrogenous bases.
Reason : Adenine and guanine are substituted pyrimidines while uracil, cytosine and thymine are substituted purines.

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To solve the question, we need to evaluate both the assertion and the reason provided. ### Step-by-Step Solution: 1. **Understanding the Assertion**: - The assertion states that "The heterocyclic compounds in nucleic acid are the nitrogenous bases." - Heterocyclic compounds are cyclic compounds that contain at least two different elements in their ring structure. In nucleic acids, the nitrogenous bases (adenine, guanine, cytosine, thymine, and uracil) are indeed heterocyclic compounds because they contain nitrogen and carbon in their structures. 2. **Evaluating the Reason**: - The reason states that "Adenine and guanine are substituted pyrimidines while uracil, cytosine, and thymine are substituted purines." - To evaluate this, we need to identify the correct classifications of these nitrogenous bases: - **Adenine and Guanine**: These are classified as purines, not pyrimidines. Purines have a two-ring structure, while pyrimidines have a single-ring structure. - **Cytosine, Uracil, and Thymine**: These are classified as pyrimidines, not purines. They have a single-ring structure. 3. **Conclusion**: - Since the assertion is correct (the nitrogenous bases are indeed heterocyclic compounds), but the reason is incorrect (adenine and guanine are purines, not pyrimidines, and cytosine, uracil, and thymine are pyrimidines, not purines), we conclude that: - **Assertion**: True - **Reason**: False ### Final Answer: - The assertion is correct, but the reason is incorrect. ---
To solve the question, we need to evaluate both the assertion and the reason provided. ### Step-by-Step Solution: 1. **Understanding the Assertion**: - The assertion states that "The heterocyclic compounds in nucleic acid are the nitrogenous bases." - Heterocyclic compounds are cyclic compounds that contain at least two different elements in their ring structure. In nucleic acids, the nitrogenous bases (adenine, guanine, cytosine, thymine, and uracil) are indeed heterocyclic compounds because they contain nitrogen and carbon in their structures. ...
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Group the following as nitrogenous bases and nucleosides: Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.

Assertion :- Adenine and Guanine are substituated purines. Reason : In Adenine and Guanine purine hetercylic ring has either amino or amino and oxy groups.

Knowledge Check

  • Assertion: Purine bases present in DNA are adenine and guanine. Reason: The base thymine is present in RNA while base uracil is present in DNA.

    A
    If both assertion and reason are true and reason is the correct explanation of assertion.
    B
    If both assertion and reason are true but reason is not the correct explanation of assertion.
    C
    If assertion is true but reason is false.
    D
    If both assertion and reason are false.

  • Assertion: The two strands of DNA are complementary to each other Reason: Adenine specifically forms hydrogen bonds with guanine whereas cytosine forms hydrogen bonds with thymine.

    A
    If both assertion and reason are true and reason is the correct explanation of assertion.
    B
    If both assertion and reason are true but reason is not the correct explanation of assertion.
    C
    If assertion is true but reason is false.
    D
    If both assertion and reason are false.

  • Assertion : Weak acids have very strong conjugate bases while strong acids have weak conjugate bases. Reason : Conjugate acid - base pair differ only by one proton.

    A
    If both assertion and reason are true and reason is the correct explanation of assertion.
    B
    If both assertion and reason are true but reason is not the correct explanation of assertion.
    C
    If assertion is true but reason is false.
    D
    If both assertion and reason are false.

    • Similar Questions

    Explore conceptually related problems

    Read the below Statements about the structure of genetic material and identify the correct ones. I. Adenine and guanine are bases that have a double ring structure , cytosine, thymine and uracil are based with a single ring structure . II. An adenine nucleotide from DNA is the same as an adenine nucleotide from RNA , DNA adenine pairs with uracil and RNA adenine pairs with thymine. III. The base pairing that occurs in a double DNA helix and when RNA is synthesised during transcription follows the rule that a purine pairs with a pyrimidine. IV. The two Polynucleotides on a DNA molecule run in opposite directions so that the double helix formed has two strands that are anti-parallel to each other.

    Substitution of a purine base with a pyrimidine base or vice versa is called

    Assertion:In a DNA molecules the total quantity of purines equals the total quantity of pyrimidines Reason : Adenine pairs with thymine and cytosine pairs with guanine

    The chemical formula of deoxyribonucleic acid (DNA) is now well established. The molecule is a very long chain, the backbone of which consists of a regular alternation of sugar and phosphate groups. 5 To each sugar is attached a nitrogenous base, which can be of four different types. Two of the possible bases—adenine and guanine—are purines, and the other two—thymine and cytosine—are pyrimidines. So far as is known, the sequence of bases along the 10 chain is irregular. The monomer unit, consisting of phosphate, sugar and base, is known as a nucleotide. The first feature of our structure which is of biological interest is that it consists not of one chain, but of two. These two chains are both coiled around 15 a common fiber axis. It has often been assumed that since there was only one chain in the chemical formula there would only be one in the structural unit. However, the density, taken with the X-ray evidence, suggests very strongly that there are two. 20. The other biologically important feature is the manner in which the two chains are held together. This is done by hydrogen bonds between the bases. The bases are joined together in pairs, a single base from one chain being hydrogen-bonded to a single 25 base from the other. The important point is that only certain pairs of bases will fit into the structure. One member of a pair must be a purine and the other a pyrimidine in order to bridge between the two chains. If a pair consisted of two purines, for 30 example, there would not be room for it. We believe that the bases will be present almost entirely in their most probable forms. If this is true, the conditions for forming hydrogen bonds are more restrictive, and the only pairs of bases possible are: 35 adenine with thymine, and guanine with cytosine. Adenine, for example, can occur on either chain, but when it does, its partner on the other chain must always be thymine. The phosphate-sugar backbone of our model is 40 completely regular, but any sequence of the pairs of bases can fit into the structure. It follows that in a long molecule many different permutations are possible, and it therefore seems likely that the precise sequence of bases is the code which carries the 45 genetical information. If the actual order of the bases on one of the pair of chains were given, one could write down the exact order of the bases on the other one, because of the specific pairing. Thus one chain is, as it were, the complement of the other, and it is 50 this feature which suggests how the deoxyribonucleic acid molecule might duplicate itself. The table shows, for various organisms, the percentage of each of the four types of nitrogenous bases in that organism’s DNA. Adapted from Manju Bansal, “DNA Structure: Revisiting the Watson-Crick Double Helix.” ©2003 by Current Science Association, Bangalore 22. The authors use the word “backbone” in lines 3 and 39 to indicate that

    The chemical formula of deoxyribonucleic acid (DNA) is now well established. The molecule is a very long chain, the backbone of which consists of a regular alternation of sugar and phosphate groups. 5 To each sugar is attached a nitrogenous base, which can be of four different types. Two of the possible bases—adenine and guanine—are purines, and the other two—thymine and cytosine—are pyrimidines. So far as is known, the sequence of bases along the 10 chain is irregular. The monomer unit, consisting of phosphate, sugar and base, is known as a nucleotide. The first feature of our structure which is of biological interest is that it consists not of one chain, but of two. These two chains are both coiled around 15 a common fiber axis. It has often been assumed that since there was only one chain in the chemical formula there would only be one in the structural unit. However, the density, taken with the X-ray evidence, suggests very strongly that there are two. 20. The other biologically important feature is the manner in which the two chains are held together. This is done by hydrogen bonds between the bases. The bases are joined together in pairs, a single base from one chain being hydrogen-bonded to a single 25 base from the other. The important point is that only certain pairs of bases will fit into the structure. One member of a pair must be a purine and the other a pyrimidine in order to bridge between the two chains. If a pair consisted of two purines, for 30 example, there would not be room for it. We believe that the bases will be present almost entirely in their most probable forms. If this is true, the conditions for forming hydrogen bonds are more restrictive, and the only pairs of bases possible are: 35 adenine with thymine, and guanine with cytosine. Adenine, for example, can occur on either chain, but when it does, its partner on the other chain must always be thymine. The phosphate-sugar backbone of our model is 40 completely regular, but any sequence of the pairs of bases can fit into the structure. It follows that in a long molecule many different permutations are possible, and it therefore seems likely that the precise sequence of bases is the code which carries the 45 genetical information. If the actual order of the bases on one of the pair of chains were given, one could write down the exact order of the bases on the other one, because of the specific pairing. Thus one chain is, as it were, the complement of the other, and it is 50 this feature which suggests how the deoxyribonucleic acid molecule might duplicate itself. The table shows, for various organisms, the percentage of each of the four types of nitrogenous bases in that organism’s DNA. Adapted from Manju Bansal, “DNA Structure: Revisiting the Watson-Crick Double Helix.” ©2003 by Current Science Association, Bangalore 29. Do the data in the table support the authors’ proposed pairing of bases in DNA?

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