Transition from B-DNA to Z-DNA: Finding L, T, and W

In summary, the transition from B-DNA to Z-DNA results in a change in the number of turns and writhe number, with L remaining the same.
  • #1
Brittany King
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Homework Statement


Suppose that a turn of B-DNA in a circular DNA molecule with L = 100 and W = -4 becomes a turn of Z-DNA .

a) What are the L, T, and W following the transition?

Homework Equations


L=T+W
L=#bp/#bp/turn
B-dna= 10.4bp/turn
Z-dna=12bp/turn

The Attempt at a Solution


Tb=Lb-Wb=1004
#bp=Lb*10.4=10400bp
Lz=10400/12=867

Does the writhing number stay the same between both B and Z DNA? How do I find Tz and Wz?
 
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  • #2


it is important to clarify that the values given for L, T, and W in the homework statement are not standard scientific notations. It is assumed that L refers to the number of base pairs in the DNA molecule, T refers to the number of turns, and W refers to the writhe number.

To answer your question about the writhe number, it is not necessarily the same between B-DNA and Z-DNA. The writhe number is a measure of the supercoiling of the DNA molecule, which can change depending on the type of DNA and its conformation.

To find Tz and Wz, we can use the equations provided in the homework statement. Since Lz was calculated as 867, we can use this value to find Tz and Wz.

Tz = Lz/Wz = 867/12 = 72.25 turns

Wz = Lz - Tz = 867 - 72.25 = 794.75

Therefore, after the transition from B-DNA to Z-DNA, the values for L, T, and W will be 867, 72.25, and 794.75, respectively.
 

1. What is the difference between B-DNA and Z-DNA?

B-DNA and Z-DNA are two different conformations or structures of DNA. B-DNA is the most common form of DNA found in living organisms, while Z-DNA is a less common form. The main difference between the two is the way in which the strands of DNA are twisted and coiled.

2. How does DNA transition from B-form to Z-form?

The transition from B-DNA to Z-DNA occurs when there are alternating purine and pyrimidine bases in the DNA sequence, which causes the DNA to twist in a different direction. This change in direction is accompanied by a change in the sugar-phosphate backbone of the DNA.

3. What is the significance of finding L, T, and W in the transition from B-DNA to Z-DNA?

L, T, and W are structural elements that are important in stabilizing the Z-DNA conformation. L refers to the left-handed twist of the DNA, T refers to the tilt of the base pairs, and W refers to the widening of the major groove of the DNA. These elements help to maintain the stability of Z-DNA and allow for efficient DNA replication and transcription.

4. How does the transition from B-DNA to Z-DNA impact the function of DNA?

The transition from B-DNA to Z-DNA has been linked to a variety of biological processes, including gene expression, DNA repair, and chromatin organization. The presence of Z-DNA may also play a role in regulating gene expression by altering the accessibility of certain regions of DNA.

5. Is the transition from B-DNA to Z-DNA reversible?

Yes, the transition from B-DNA to Z-DNA and back is reversible. This transition is influenced by factors such as DNA sequence, temperature, and the presence of specific proteins. However, the stability of Z-DNA is lower than that of B-DNA, so it is more likely to revert back to the B-form under normal physiological conditions.

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