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A relaxed circular plasmid has linking number 200. The plasmid is transformed in E. coli cells and re-isolated. The newly isolated plasmid was found to be supercoiled negatively by +20 writhe value. The number of helix turns in the new plasmid would be _________
Correct answer is '180'. Can you explain this answer?
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A relaxed circular plasmid has linking number 200. The plasmid is tran...
Linking no. (Lk) = Twist + writhe. The Lk of the circular DNA remains unchanged if the DNA is not broken and re-joined. So the Lk of the new plasmid would remain same = 200 = twist + 20; New twist = 200-20 = 180.
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A relaxed circular plasmid has linking number 200. The plasmid is tran...
Given:
- A relaxed circular plasmid has a linking number of 200.
- The plasmid is transformed in E. coli cells and re-isolated.
- The newly isolated plasmid is supercoiled negatively with a writhe value of 20.
To find:
The number of helix turns in the new plasmid.
Solution:
1. Understanding Linking Number:
The linking number is a topological property of a closed circular DNA molecule. It represents the number of times one strand of DNA crosses over or under the other strand. In the case of a relaxed circular DNA molecule, the linking number is equal to the total number of base pairs divided by the number of base pairs per helical turn.
2. Impact of Transformation and Re-isolation:
When a plasmid is transformed into E. coli cells and re-isolated, it undergoes various processes such as replication, transcription, and recombination. These processes can introduce changes in the plasmid's topology, leading to supercoiling.
3. Negative Supercoiling:
Negative supercoiling refers to the twisting of the DNA molecule in the opposite direction to its natural helical twist. It is characterized by a decrease in the linking number. In the given question, the newly isolated plasmid is supercoiled negatively with a writhe value of 20.
4. Relationship between Linking Number and Writhe:
The linking number (Lk) can be expressed as the sum of the twist (Tw) and the writhe (Wr) of a DNA molecule.
Lk = Tw + Wr
In the case of supercoiling, the linking number (Lk) changes while the twist (Tw) remains constant. Therefore, we can calculate the change in the linking number (ΔLk) using the writhe value (Wr):
ΔLk = Wr
5. Calculating the Number of Helix Turns:
To find the number of helix turns in the new plasmid, we need to calculate the change in linking number (ΔLk) and subtract it from the initial linking number (Lk).
ΔLk = 20
Lk = 200
Number of helix turns = Lk - ΔLk
Number of helix turns = 200 - 20 = 180
Therefore, the number of helix turns in the new plasmid is 180.
- A relaxed circular plasmid has a linking number of 200.
- The plasmid is transformed in E. coli cells and re-isolated.
- The newly isolated plasmid is supercoiled negatively with a writhe value of 20.
To find:
The number of helix turns in the new plasmid.
Solution:
1. Understanding Linking Number:
The linking number is a topological property of a closed circular DNA molecule. It represents the number of times one strand of DNA crosses over or under the other strand. In the case of a relaxed circular DNA molecule, the linking number is equal to the total number of base pairs divided by the number of base pairs per helical turn.
2. Impact of Transformation and Re-isolation:
When a plasmid is transformed into E. coli cells and re-isolated, it undergoes various processes such as replication, transcription, and recombination. These processes can introduce changes in the plasmid's topology, leading to supercoiling.
3. Negative Supercoiling:
Negative supercoiling refers to the twisting of the DNA molecule in the opposite direction to its natural helical twist. It is characterized by a decrease in the linking number. In the given question, the newly isolated plasmid is supercoiled negatively with a writhe value of 20.
4. Relationship between Linking Number and Writhe:
The linking number (Lk) can be expressed as the sum of the twist (Tw) and the writhe (Wr) of a DNA molecule.
Lk = Tw + Wr
In the case of supercoiling, the linking number (Lk) changes while the twist (Tw) remains constant. Therefore, we can calculate the change in the linking number (ΔLk) using the writhe value (Wr):
ΔLk = Wr
5. Calculating the Number of Helix Turns:
To find the number of helix turns in the new plasmid, we need to calculate the change in linking number (ΔLk) and subtract it from the initial linking number (Lk).
ΔLk = 20
Lk = 200
Number of helix turns = Lk - ΔLk
Number of helix turns = 200 - 20 = 180
Therefore, the number of helix turns in the new plasmid is 180.
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A relaxed circular plasmid has linking number 200. The plasmid is transformed in E. coli cells and re-isolated. The newly isolated plasmid was found to be supercoiled negatively by +20 writhe value. The number of helix turns in the new plasmid would be _________Correct answer is '180'. Can you explain this answer?
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A relaxed circular plasmid has linking number 200. The plasmid is transformed in E. coli cells and re-isolated. The newly isolated plasmid was found to be supercoiled negatively by +20 writhe value. The number of helix turns in the new plasmid would be _________Correct answer is '180'. Can you explain this answer? for IIT JAM 2024 is part of IIT JAM preparation. The Question and answers have been prepared according to the IIT JAM exam syllabus. Information about A relaxed circular plasmid has linking number 200. The plasmid is transformed in E. coli cells and re-isolated. The newly isolated plasmid was found to be supercoiled negatively by +20 writhe value. The number of helix turns in the new plasmid would be _________Correct answer is '180'. Can you explain this answer? covers all topics & solutions for IIT JAM 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A relaxed circular plasmid has linking number 200. The plasmid is transformed in E. coli cells and re-isolated. The newly isolated plasmid was found to be supercoiled negatively by +20 writhe value. The number of helix turns in the new plasmid would be _________Correct answer is '180'. Can you explain this answer?.
A relaxed circular plasmid has linking number 200. The plasmid is transformed in E. coli cells and re-isolated. The newly isolated plasmid was found to be supercoiled negatively by +20 writhe value. The number of helix turns in the new plasmid would be _________Correct answer is '180'. Can you explain this answer? for IIT JAM 2024 is part of IIT JAM preparation. The Question and answers have been prepared according to the IIT JAM exam syllabus. Information about A relaxed circular plasmid has linking number 200. The plasmid is transformed in E. coli cells and re-isolated. The newly isolated plasmid was found to be supercoiled negatively by +20 writhe value. The number of helix turns in the new plasmid would be _________Correct answer is '180'. Can you explain this answer? covers all topics & solutions for IIT JAM 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A relaxed circular plasmid has linking number 200. The plasmid is transformed in E. coli cells and re-isolated. The newly isolated plasmid was found to be supercoiled negatively by +20 writhe value. The number of helix turns in the new plasmid would be _________Correct answer is '180'. Can you explain this answer?.
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A relaxed circular plasmid has linking number 200. The plasmid is transformed in E. coli cells and re-isolated. The newly isolated plasmid was found to be supercoiled negatively by +20 writhe value. The number of helix turns in the new plasmid would be _________Correct answer is '180'. Can you explain this answer?, a detailed solution for A relaxed circular plasmid has linking number 200. The plasmid is transformed in E. coli cells and re-isolated. The newly isolated plasmid was found to be supercoiled negatively by +20 writhe value. The number of helix turns in the new plasmid would be _________Correct answer is '180'. Can you explain this answer? has been provided alongside types of A relaxed circular plasmid has linking number 200. The plasmid is transformed in E. coli cells and re-isolated. The newly isolated plasmid was found to be supercoiled negatively by +20 writhe value. The number of helix turns in the new plasmid would be _________Correct answer is '180'. Can you explain this answer? theory, EduRev gives you an
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