Nucleic Acids Questions in English

(B) $RNA$ contains ribose sugar and nitrogenous bases: adenine,guanine,cytosine,and uracil.

(D) In nucleic acids,a unit formed by the combination of a nitrogenous base,a pentose sugar,and a phosphate group is known as a $Nucleotide$.
$A$ $Nucleoside$ consists only of a nitrogenous base and a pentose sugar.
Therefore,the correct option is $D$.

(A) In the structure of $DNA$,the two strands of the double helix are held together by hydrogen bonds between the nitrogenous bases. Specifically,$Adenine$ $(A)$ pairs with $Thymine$ $(T)$ via two hydrogen bonds,and $Guanine$ $(G)$ pairs with $Cytosine$ $(C)$ via three hydrogen bonds.

(C) nucleic acid is a polymer of nucleotides. Each nucleotide consists of three components: a nitrogenous base,a pentose sugar,and a phosphate group. The nitrogenous base is attached to the $1'$ position of the sugar,and the phosphate group is attached to the $5'$ position of the sugar. Therefore,the structural sequence within a nucleotide unit is Base $\rightarrow$ Sugar $\rightarrow$ Phosphate.

(A) In $DNA$,the base pairing rule is $A-T$ and $G-C$.
During transcription,$DNA$ is transcribed into $RNA$.
In $RNA$,$Uracil$ $(U)$ replaces $Thymine$ $(T)$.
Therefore,the base pairing for $RNA$ synthesis from $DNA$ is $A-U$,$T-A$,$G-C$,and $C-G$.
Given $DNA$ sequence: $T-G-A-A-C-C-C-T-T$.
Complementary $RNA$ sequence: $A-C-U-U-G-G-G-A-A$.

(D) nucleotide is the basic structural unit of nucleic acids like $DNA$ and $RNA$. It consists of three essential components:
$1$. $A$ pentose sugar (ribose or deoxyribose).
$2$. $A$ nitrogenous base (purine or pyrimidine).
$3$. $A$ phosphoric acid group.
Therefore,all the given components are present in a nucleotide.

(C) In a nucleotide,the sugar molecule (ribose or deoxyribose) is linked to a heterocyclic base at the $C'_1$ position.
The phosphate group is linked to the sugar molecule through an ester linkage at the $C'_5$ position.
Therefore,the heterocyclic base is at $C'_1$ and the phosphate ester linkage is at $C'_5$ of the sugar molecule.

(D) nucleotide consists of a nitrogenous base,a pentose sugar,and a phosphate group.
The common nitrogenous bases found in nucleotides are adenine,guanine,cytosine,thymine,and uracil.
Tyrosine is an amino acid,not a nitrogenous base,and therefore it is not present in a nucleotide.

(D) $RNA$ (Ribonucleic acid) contains the sugar $\beta-D-ribose.$
$DNA$ (Deoxyribonucleic acid) contains the sugar $\beta-D-2'-deoxyribose.$
Therefore,the correct statement is that the sugar component in $RNA$ is ribose and the sugar component in $DNA$ is $2'-$deoxyribose.

(B) In $DNA$,the two strands are held together by hydrogen bonds between the complementary nitrogenous bases. Adenine $(A)$ pairs with Thymine $(T)$ via two hydrogen bonds,and Guanine $(G)$ pairs with Cytosine $(C)$ via three hydrogen bonds. Therefore,the linkages between different nitrogenous bases are $H$-bonding.

(B) The segment of $DNA$ which acts as the instrumental manual for the synthesis of the protein is a $gene$.
Every protein in a cell has a corresponding $gene$ that contains the information required for its synthesis.

(C) $DNA$ has a double helical structure.
These helices contain polynucleotide chains,and these chains are held together by hydrogen bonds.
In the $DNA$ double helix,adenine $(A)$ always pairs with thymine $(T)$ via two hydrogen bonds,and guanine $(G)$ always pairs with cytosine $(C)$ via three hydrogen bonds.

(C) $RNA$ and $DNA$ molecules contain ribose and deoxyribose sugars, respectively.
Both sugars possess multiple chiral centers.
The chirality of these nucleic acids is primarily attributed to the presence of the $D$-sugar component (specifically $D$-ribose in $RNA$ and $D$-2-deoxyribose in $DNA$).

(A) $DNA$ contains two types of nitrogenous bases: purines and pyrimidines.
The purines are adenine $(A)$ and guanine $(G)$.
The pyrimidines present in $DNA$ are cytosine $(C)$ and thymine $(T)$.
In $RNA$,thymine is replaced by uracil $(U)$.
Therefore,the pyrimidine bases in $DNA$ are cytosine and thymine.

(B) The sugar molecule found in $RNA$ is $D$-ribose,while the sugar in $DNA$ is $D$-$2$-deoxyribose.
$D$-$2$-deoxyribose differs from ribose only in the substitution of a hydrogen atom for an $-OH$ group at the $2$-position,as shown in the figure.

(A) Quinoline is an alkaloid and is not present in $DNA$.
$DNA$ contains four nitrogenous bases: adenine,guanine,cytosine,and thymine.

(C) Nucleic acids contain two types of nitrogenous bases: purines and pyrimidines.
$RNA$ contains two purines: Adenine $(A)$ and Guanine $(G)$.
$RNA$ contains two pyrimidines: Cytosine $(C)$ and Uracil $(U)$.
Since Adenine and Guanine are purines,the correct pyrimidine base present in $RNA$ among the options is Uracil.

(C) $Uracil$ is the nitrogenous base present only in $RNA$,but not in $DNA$.
$DNA$ contains thymine,guanine,adenine,and cytosine.
In $RNA$,thymine is replaced by $Uracil$.

(C) nucleotide consists of three components: a nitrogenous base,a pentose sugar,and a phosphate group.
In the structure of a nucleotide,the nitrogenous base is attached to the $C-1$ position of the pentose sugar.
The phosphate group is attached to the $C-5$ position of the pentose sugar through an ester linkage.
Therefore,the correct option is $C$.

(B) $DNA$ contains the nitrogenous bases Adenine $(A)$,Guanine $(G)$,Cytosine $(C)$,and Thymine $(T)$.
$RNA$ contains the nitrogenous bases Adenine $(A)$,Guanine $(G)$,Cytosine $(C)$,and Uracil $(U)$.
Therefore,Uracil is the base present in $RNA$ but absent in $DNA$,while Thymine is present in $DNA$ but absent in $RNA$.

(A) During the process of transcription,the $DNA$ template strand is used to synthesize a complementary $RNA$ strand.
In $RNA$,the base $Uracil$ $(U)$ replaces $Thymine$ $(T)$ found in $DNA$.
Given $DNA$ sequence: $A-T-T-G-A-C-G-C-A-T$.
The complementary $RNA$ sequence will be: $U-A-A-C-U-G-C-G-U-A$.

(C) nucleotide consists of a sugar (deoxyribose or ribose),a phosphate group,and a nitrogenous base (such as guanine,cytosine,adenine,or thymine/uracil).
Glycine is an amino acid,not a component of a nucleotide.

(A) The basicity of a nitrogen-containing compound depends on the availability of the lone pair of electrons for protonation.
In the given structure (purine derivative):
- Nitrogen $1$,$3$,and $4$ have lone pairs that are in $sp^2$ hybridized orbitals and are not involved in the aromatic sextet,making them available for protonation.
- Nitrogen $2$ has a lone pair that is part of the aromatic system (it participates in the $6\pi$ electron delocalization required for aromaticity).
- Since the lone pair on nitrogen $2$ is involved in resonance to maintain aromaticity,it is not available for donation to a proton.
- Therefore,nitrogen $2$ does not contribute to the basicity of the compound.

(B) In $DNA$,the complementary base pairing follows the rule: $A$ pairs with $T$ and $C$ pairs with $G$.
Given the strand sequence: $C-T-G-T-C-A-G-T-A$.
Replacing each base with its complement:
$C \rightarrow G$
$T \rightarrow A$
$G \rightarrow C$
$T \rightarrow A$
$C \rightarrow G$
$A \rightarrow T$
$G \rightarrow C$
$T \rightarrow A$
$A \rightarrow T$
Thus,the complementary sequence is $GACAGTCAT$.

(D) In the double-strand helix structure of $DNA,$ the nitrogenous bases pair according to Chargaff's rules.
Thymine $(T)$ always forms two hydrogen bonds with Adenine $(A).$
Cytosine $(C)$ always forms three hydrogen bonds with Guanine $(G).$
Therefore,thymine forms hydrogen bonds with adenine.

(D) The two polynucleotide chains of $DNA$ molecules are twisted around a common axis but run in opposite directions to form a right-handed helix.
These two chains are held together by specific hydrogen bonds between the complementary nitrogenous bases ($A$ pairs with $T$,and $G$ pairs with $C$).

(A) $1$. $RNA$ (Ribonucleic acid) is primarily responsible for protein synthesis in the cell.
$2$. The sugar present in $DNA$ is $2$-deoxy-$D$-ribose,not $D-(-)$-ribose (which is found in $RNA$).
$3$. $DNA$ typically has a double-stranded helix structure,whereas $RNA$ is usually single-stranded.
$4$. $DNA$ is primarily found in the nucleus of the cell,while $RNA$ is found in the cytoplasm and nucleus.
Therefore,the correct statement is that $RNA$ controls the synthesis of proteins.

(B) $RNA$ (Ribonucleic acid) contains four nitrogenous bases: Adenine,Guanine,Cytosine,and Uracil.
Option $A$ represents Cytosine,which is found in both $DNA$ and $RNA$.
Option $B$ represents Uracil,which is specifically found in $RNA$ and replaces Thymine found in $DNA$.
Option $C$ represents Thymine,which is found in $DNA$.
Option $D$ represents $1,3$-Dimethyluracil,which is not a naturally occurring base in $RNA$.
Therefore,both $A$ and $B$ are found in $RNA$. However,Uracil $(B)$ is the characteristic base that distinguishes $RNA$ from $DNA$.

(A) $RNA$ is typically single-stranded and does not form a double-stranded $\alpha - \text{helix}$ structure like $DNA$. Therefore,the statement that it always has a double-stranded $\alpha - \text{helix}$ structure is incorrect.

(A) nucleotide is formed by the esterification of a nucleoside with a phosphate group at the $5'$-$OH$ position of the sugar. This statement is correct.
$(B)$ $A$ nucleoside is formed by the attachment of a nitrogenous base to the $1'$-position of a pentose sugar ($ribose$ or $deoxyribose$). This statement is correct.
$(C)$ $DNA$ contains $2$-deoxyribose sugar and thymine,whereas $RNA$ contains ribose sugar and uracil. Thus,they differ in both sugar and nitrogenous base. This statement is correct.
$(D)$ In $DNA$ double helix,adenine $(A)$ pairs with thymine $(T)$ via two hydrogen bonds $(A=T)$,and cytosine $(C)$ pairs with guanine $(G)$ via three hydrogen bonds $(C \equiv G)$. This statement is correct.
Therefore,all statements $(A), (B), (C),$ and $(D)$ are correct.

(D) The constituents of nucleic acids are nitrogenous bases,sugar,and phosphoric acid.
The sugar present in $DNA$ is $D(-)-2$-deoxyribose and the sugar present in $RNA$ is $D(-)$-ribose.
Due to these $D$-sugar components,$DNA$ and $RNA$ molecules are chiral molecules.

(D) $RNA$ contains the bases $Adenine$ $(A)$,$Uracil$ $(U)$,$Guanine$ $(G)$,and $Cytosine$ $(C)$.
$DNA$ contains the bases $Adenine$ $(A)$,$Thymine$ $(T)$,$Guanine$ $(G)$,and $Cytosine$ $(C)$.
Therefore,$Uracil$ $(U)$ is the base present in $RNA$ but not in $DNA$.

(D) Wool,nails,and hair are primarily composed of fibrous proteins like keratin.
$DNA$ (Deoxyribonucleic acid) is a nucleic acid,not a protein.
Therefore,the correct answer is $DNA$.

(C) Nucleic acids are of two types: $DNA$ (Deoxyribonucleic acid) and $RNA$ (Ribonucleic acid).
Both $DNA$ and $RNA$ contain four nitrogenous bases.
The nitrogenous bases in $DNA$ are Adenine $(A)$,Guanine $(G)$,Cytosine $(C)$,and Thymine $(T)$.
The nitrogenous bases in $RNA$ are Adenine $(A)$,Guanine $(G)$,Cytosine $(C)$,and Uracil $(U)$.
Therefore,Adenine is present in both $DNA$ and $RNA$.

(A) In $DNA$ double helix,the two strands are complementary to each other based on base pairing rules: $A$ pairs with $T$ and $C$ pairs with $G$.
Given sequence: $A-T-G-C-T-T-G-A$.
Complementary sequence:
$A$ pairs with $T$
$T$ pairs with $A$
$G$ pairs with $C$
$C$ pairs with $G$
$T$ pairs with $A$
$T$ pairs with $A$
$G$ pairs with $C$
$A$ pairs with $T$
Thus,the complementary sequence is $TACGAACT$.

(B) In $DNA$,the nitrogenous bases pair specifically according to Chargaff's rules.
Adenine $(A)$ always pairs with Thymine $(T)$ via two hydrogen bonds.
Guanine $(G)$ always pairs with Cytosine $(C)$ via three hydrogen bonds.
Therefore,the complementary base pairs are $A-T$ and $G-C$.

(D) Nucleic acids ($DNA$ and $RNA$) contain nitrogenous bases derived from purines and pyrimidines.
The common purines are Adenine $(A)$ and Guanine $(G)$.
The common pyrimidines are Cytosine $(C)$,Thymine $(T)$,and Uracil $(U)$.
Guanidine is a chemical compound with the formula $HNC(NH_2)_2$,which is not a nitrogenous base found in nucleic acids.
Therefore,the correct answer is Guanidine.

(D) $Gene$ is a specific segment of $DNA$ that contains the instructions for the synthesis of a particular protein.
It acts as the functional unit of heredity and carries the genetic information required for protein synthesis.

(D) nucleotide is the basic structural unit of nucleic acids like $DNA$ and $RNA$. It consists of three components:
$1$. $A$ pentose sugar (ribose or deoxyribose).
$2$. $A$ nitrogenous base (purine or pyrimidine).
$3$. $A$ phosphate group.
Therefore,all the given options are correct.

(D) chemical change in the $DNA$ molecule that alters the genetic code is known as a $Mutation$.
This change can lead to a different amino acid being incorporated into the protein chain during protein synthesis,potentially affecting the structure and function of the resulting protein.

(A) Chargaff's rule states that in any double-stranded $DNA$ molecule,the total amount of purines equals the total amount of pyrimidines.
Specifically,the amount of $Adenine$ $(A)$ is equal to the amount of $Thymine$ $(T)$,and the amount of $Guanine$ $(G)$ is equal to the amount of $Cytosine$ $(C)$.
Therefore,the ratio $[A+G]/[T+C] = 1$ and $[A+T]/[G+C]$ is variable.

(B) Adenosine is formed by the attachment of a nitrogenous base (adenine) to a sugar molecule (ribose) at the $1'$ position.
Since it consists only of a nitrogenous base and a sugar without a phosphate group,it is classified as a nucleoside.
Therefore,the correct option is $B$.

(C) The $DNA$ molecule consists of two polynucleotide strands that are complementary to each other,not identical.
Each strand contains a sequence of nitrogenous bases that pair specifically ($A$ with $T$,$G$ with $C$).
Therefore,the statement that the two strands are identical is false.

(D) The relationship between the sequence of nucleotide triplets (codons) in $mRNA$ and the specific amino acids they encode is known as the $Genetic \ code$.
Each triplet of nucleotides corresponds to a specific amino acid,which forms the basis of protein synthesis.

(C) Nucleic acids contain two types of nitrogenous bases: purines and pyrimidines.
Purines include $Adenine$ $(A)$ and $Guanine$ $(G)$.
Pyrimidines include $Cytosine$ $(C)$,$Thymine$ $(T)$,and $Uracil$ $(U)$.
Therefore,$Guanine$ is a purine derivative.

(C) In the genetic code,a sequence of $3$ nucleotides (a triplet) in messenger $RNA$ $(mRNA)$ specifies a particular amino acid. This sequence of $3$ nucleotides is known as a codon.

(C) nucleotide is composed of three components: a nitrogenous base,a pentose sugar,and a phosphate group.
In the structure of a nucleotide,the nitrogenous base is attached to the $C1'$ position of the pentose sugar,and the phosphate group is attached to the $C5'$ position of the same sugar.
Therefore,the structural arrangement is $Base-Sugar-Phosphate$.

(C) $RNA$ (Ribonucleic acid) consists of a ribose sugar,a phosphate group,and nitrogenous bases: Adenine $(A)$,Guanine $(G)$,Cytosine $(C)$,and Uracil $(U)$.
Thymine $(T)$ is present in $DNA$ but is replaced by Uracil in $RNA$.