Question:
In a nucleotide sequence ATGC, which of the following nucleotide has the unlinked 5' - OH?
In a nucleotide sequence ATGC, which of the following nucleotide has the unlinked 5' - OH?
Show Hint
Always read nucleotide sequences from left to right as $5'$ to $3'$. The first letter (A, in ATGC) represents the $5'$ terminal nucleotide with the unlinked $5'$-OH/phosphate group, and the last letter (G) represents the $3'$ terminal end with the unlinked $3'$-OH.
Updated On: Jul 23, 2026
- deoxyadenylate
- deoxycytidylate
- deoxythymidylate
- deoxyguanylate
Show Solution
Verified By Collegedunia
The Correct Option is A
Solution and Explanation
Step 1: Understanding the Concept:
Polynucleotide chains (DNA and RNA) are polar structures.
By scientific convention, nucleotide sequences are written and read in the $5'$ to $3'$ direction unless specified otherwise.
Step 2: Detailed Explanation:
Let us analyze the chemical structure and directionality of the given tetranucleotide sequence $5'-\text{ATGC}-3'$:
- In any standard DNA strand, the $5'$ end of the first nucleotide has a free, unlinked $5'$ hydroxyl (or $5'$ phosphate) group.
- The $3'$ hydroxyl group of this first nucleotide is covalently linked via a phosphodiester bond to the $5'$ phosphate of the next nucleotide, continuing down the chain.
- The last nucleotide at the $3'$ end of the sequence has a free, unlinked $3'$ hydroxyl group.
In the sequence ATGC:
- Deoxyadenylate (A) is the first nucleotide at the $5'$ terminus, meaning it possesses the free, unlinked $5'$ hydroxyl group.
- Deoxythymidylate (T) is the second nucleotide.
- Deoxycytidylate (C) is the third nucleotide.
- Deoxyguanylate (G) is the last nucleotide at the $3'$ terminus, possessing the free, unlinked $3'$ hydroxyl group.
Therefore, deoxyadenylate has the unlinked $5'$ hydroxyl group.
Step 3: Final Answer:
The nucleotide with the unlinked $5'$ hydroxyl group is deoxyadenylate.
Polynucleotide chains (DNA and RNA) are polar structures.
By scientific convention, nucleotide sequences are written and read in the $5'$ to $3'$ direction unless specified otherwise.
Step 2: Detailed Explanation:
Let us analyze the chemical structure and directionality of the given tetranucleotide sequence $5'-\text{ATGC}-3'$:
- In any standard DNA strand, the $5'$ end of the first nucleotide has a free, unlinked $5'$ hydroxyl (or $5'$ phosphate) group.
- The $3'$ hydroxyl group of this first nucleotide is covalently linked via a phosphodiester bond to the $5'$ phosphate of the next nucleotide, continuing down the chain.
- The last nucleotide at the $3'$ end of the sequence has a free, unlinked $3'$ hydroxyl group.
In the sequence ATGC:
- Deoxyadenylate (A) is the first nucleotide at the $5'$ terminus, meaning it possesses the free, unlinked $5'$ hydroxyl group.
- Deoxythymidylate (T) is the second nucleotide.
- Deoxycytidylate (C) is the third nucleotide.
- Deoxyguanylate (G) is the last nucleotide at the $3'$ terminus, possessing the free, unlinked $3'$ hydroxyl group.
Therefore, deoxyadenylate has the unlinked $5'$ hydroxyl group.
Step 3: Final Answer:
The nucleotide with the unlinked $5'$ hydroxyl group is deoxyadenylate.
Was this answer helpful?
0
0
Top ICAR AIEEA Plant Biotechnology Questions
- Which of the following molecules can be classified under glycosphingolipid category?
- The bicarbonate buffer is a principal buffering system in blood plasma. The ratio of the bicarbonate to carbonic acid required to maintain pH of plasma at 7.4 is:
- Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A): The disruption of $\beta$-oxidation of fatty acids in plants can potentially reduce stress-induced ROS accumulation and improve its stress tolerance.
Reason (R): In plants, $\beta$-oxidation of fatty acids takes place predominantly in peroxisomes, where first enzyme of $\beta$-oxidation viz. fatty acyl CoA oxidase produces large amounts of hydrogen peroxide.
In light of the above statements, choose the correct answer from the options given below. - The serum level of which of the following metabolites can effectively distinguish "Vitamin B12 deficiency" from "Folate deficiency" ?
- Match List-I with List-II
List-I (Name of the Enzyme) & List-II (Class of the enzyme)
(A). Pyruvate carboxylase & (I). Oxidoreductase
(B). Fumarase & (II). Hydrolase
(C). Phospholipase & (III). Lyase
(D). Nitrogenase & (IV). Ligase
Choose the correct answer from the options given below:
View More Questions
Top ICAR AIEEA Molecular Biology Questions
- The products of which of the following pair of nif genes control the expression of other nif genes?
- Match List-I with List-II
List-I (Form of DNA) & List-II (Characteristic of DNA)
(A). A-DNA & (II). Short, broad and right-handed
(B). B-DNA & (III). Longer, thinner and right-handed
(C). Z-DNA & (IV). Anti conformation at Cytosine and syn at Guanine
(D). H-DNA & (I). Triplex DNA
Choose the correct answer from the options given below: - Which of the following condition will favour synthesis of $\beta$-galactosidase in E. coli cells
- Conventionally the -10 ($5'$-TATAAT) and -35 ($5'$-TTGACA) regions are denoted in
- Which of the following formulae may be used to estimate the concentration of RNA by UV spectrophotometer
View More Questions
Top ICAR AIEEA Questions
- Which of the following statements is false?
- Which of the following is an example of an inventory?
- According to Adam Smith, productivity gains could be brought about through .
- The supply curve for an artificially scarce good is .
- Which of the following would not be considered an opportunity cost of paid employment?
View More Questions