Question

31. The fluoroquinolone family of antibiotics (the most famous of which is ciprofloxacin, better known as Cipro), work by allowing bacterial topoisomerase to start working and cut one DNA strand, but prevents the next steps from working. It specifically targets the bacterial version of topoisomerase so it does not affect the host cell function,
    1. Draw a diagram showing the function of topoisomerase  (DNA gyrase)
    2. Explain what would happen to the bacterial cells when treated with the drug (be specific).
32. Choose which sentence below is most accurate in describing the genetic material of both prokaryotes and eukaryotes:
    1. DNA, single stranded, antiparallel, (A=G),(C=T)
    2. RNA, double stranded, parallel, (A=G),(C=T)
    3. DNA, double stranded, antiparallel, (A=G),(C=T)
    4. DNA, double stranded, antiparallel, (A=T),(C=G)
    5. DNA, double stranded, parallel, (A=T),(C=G)
    6. DNA, single stranded, antiparallel, (A=T),(C=G)

Answer 1

Solution:

B) DNA gyrase  is an emzyme which induces double stranded breaks in DNA. This prossess of inducing breaks followed by ligation,decreases the linking number and induces negative supercoiling in DNA. This prossess is essential for the condensation of chromosome as well as for the execution of replication since this reduces torsional strain during replication. If the bacterial cells are treated with inhibiting drugs like ciprofloxacin, this would inhibits the ligation prossess of breaks produced by the DNA gyrase enzyme. This affects the stability of the DNA and eventually leads to its degradation. More specifically the inhibition of DNA gyrase by inhibitors results in the cessation of DNA synthesis and bacterial growth.

The genetic material of both prokaryotes and eukaryotes are option e) DNA, double stranded, parallel, (A=T),(C=G).

Eukaryotes and prokaryotes have dsDNA as their genetic material. The two strands are arranged complementary and antiparallel in nature. The amount of Adenine in on strand equals the amount of Thymine in the opposite strand. Also the amount of Cytosine in on strand equals the amount of Guanine in the opposite strand​​​​​​​.

Answer 2

Diagram showing the function of topoisomerase (DNA gyrase):

mathematicaCopy code  Before Topoisomerase Action       After Topoisomerase Action
    (Relaxed DNA Strand)           (Supercoiled DNA Strand)
   __________|__________          ____/________\______
  /                          \        /                  \ /                            \      /                    \________________________
       DNA Strand

Explanation of Topoisomerase Action:Topoisomerase, specifically DNA gyrase in bacteria, is an enzyme responsible for the regulation of DNA supercoiling. In the "Before Topoisomerase Action" diagram, the DNA strand is represented as a straight, relaxed line. During processes like DNA replication and transcription, the DNA double helix can become tightly wound or overwound (supercoiled), leading to potential problems in replication and gene expression.

Topoisomerase works by cutting one of the DNA strands, passing the other strand through the cut, and then resealing the cut. This action relieves the strain caused by supercoiling and helps maintain the proper structure and accessibility of the DNA molecule for essential cellular processes.

Effect of Fluoroquinolone (e.g., Cipro) on Bacterial Cells:Fluoroquinolones, such as ciprofloxacin, target bacterial topoisomerase (DNA gyrase) specifically. When bacterial cells are treated with these antibiotics, they interfere with the normal functioning of DNA gyrase. While they allow the enzyme to start cutting one DNA strand, they prevent the resealing step, leading to a buildup of broken DNA strands.

As a result, the bacterial cells' ability to perform essential DNA replication and transcription processes is severely compromised. The accumulation of broken DNA leads to genetic damage and ultimately disrupts bacterial growth and division. This disruption eventually leads to bacterial cell death, effectively inhibiting the growth of the bacteria and treating the infection.

Most Accurate Sentence Describing Genetic Material of Prokaryotes and Eukaryotes:DNA, double stranded, antiparallel, (A=T),(C=G)

Explanation: In both prokaryotes and eukaryotes, the genetic material is DNA, which is composed of two strands that run in opposite directions (antiparallel). The complementary base pairing is as follows: Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G).

Answer 3

Diagram showing the function of bacterial topoisomerase (DNA gyrase):

bashCopy code    5'----|     |-----3'
          |     |
3'----|     |-----5'
    5'----|     |-----3'
          |     |
3'----|     |-----5'

Explanation of what happens to bacterial cells when treated with fluoroquinolone (Cipro):

Fluoroquinolone antibiotics, such as Cipro, specifically target bacterial topoisomerase (DNA gyrase), which is an enzyme responsible for unwinding and supercoiling DNA during replication and transcription in bacterial cells. When the drug is introduced into the bacterial cells, it binds to the bacterial topoisomerase and prevents it from completing its usual function.

Specifically, fluoroquinolones allow bacterial topoisomerase to initially make a cut in one DNA strand as part of its normal function. However, the drug then inhibits the enzyme's ability to reseal the cut and prevent the DNA strand from rejoining. This leads to the accumulation of DNA breaks in the bacterial genome, resulting in the disruption of DNA replication and transcription processes.

As a consequence, the bacterial cells are unable to properly replicate and transcribe their genetic material. This disruption severely impairs the bacterial cell's ability to grow and reproduce, ultimately leading to cell death.

Sentence describing the genetic material of both prokaryotes and eukaryotes:

"DNA, double stranded, antiparallel, (A=T),(C=G)"

This sentence accurately describes the genetic material of both prokaryotes (e.g., bacteria) and eukaryotes (e.g., plants, animals, and fungi). DNA in both prokaryotes and eukaryotes consists of two strands that run in opposite directions (antiparallel), and the complementary base pairing is Adenine (A) with Thymine (T) and Cytosine (C) with Guanine (G).