Concept explainers
In bacteriophages and bacteria, the DNA is almost always organized into circular (closed loops) chromosomes. Phage λ is an exception, maintaining its DNA in a linear chromosome within the viral particle. However, as soon as this DNA is injected into a host cell, it circularizes before replication begins. What advantage exists in replicating circular DNA molecules compared to linear molecules, characteristic of eukaryotic chromosomes?
HINT: This problem involves cm understanding of eukaryotic
To explain: The advantages of replication of DNA in a circular form compared to the linear form.
Introduction: In almost all the organisms, DNA is the genetic material that is inherited from one generation to the next. Depending on the species, DNA exists as a linear or circular molecule. In bacterial species, almost always, DNA is present as a circular chromosome. Viruses contain either DNA or RNA as their genetic material.
Explanation of Solution
In bacterial species, DNA is mostly present in circular form rather than linear form. Circular DNA serves certain advantages over the linear form. Some of the advantages of circular DNA over linear DNA are as follows:
- Circular DNA molecules are more stable compared to the linear molecules.
- End regions of linear DNA are more prone to degradation by intracellular enzymes.
- Linear DNA molecules have an unprotected OH group. This increases the chances of chemical degradation of linear DNA molecules.
- Circular DNA does not show DNA loss, as seen in linear DNA molecules. Linear DNA has telomerase, which shortens after every cell cycle.
Thus, circular DNA is more advantageous than linear DNA because it is more stable than the linear DNA molecules.
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Chapter 12 Solutions
Concepts of Genetics (12th Edition)
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