Cohesive end

Cohesive Ends or Sticky Ends are terms used in Molecular Biology and Genetics to describe the single-stranded overhangs produced on the ends of DNA molecules after the action of certain restriction enzymes. These enzymes, also known as restriction endonucleases, cut DNA at specific recognition sites, which can result in overhanging sequences at the ends of the DNA fragments. These overhangs can be complementary to each other, allowing for the annealing of DNA fragments with matching cohesive ends, which is a critical step in various molecular cloning techniques.

Overview

Cohesive ends result from the action of restriction enzymes that make staggered cuts in the two strands of the DNA double helix. The nature of these cuts leaves a short sequence of unpaired nucleotides at the end of each DNA fragment, which can base pair with any complementary sequence. This property is exploited in DNA Cloning and Recombinant DNA technologies to join DNA fragments from different sources, forming recombinant DNA molecules.

Function in Molecular Cloning

In molecular cloning, DNA fragments with cohesive ends can be joined together using the enzyme DNA Ligase, which forms covalent bonds between the sugar-phosphate backbones of adjacent DNA fragments. This process, known as ligation, is fundamental in the construction of recombinant DNA molecules. Cohesive ends ensure that DNA fragments from different sources can be precisely joined together, provided they have been cut with the same or compatible restriction enzymes.

Types of Restriction Enzymes

Restriction enzymes are classified into several types based on their structure, specificity, and mechanism of action. The most commonly used restriction enzymes in molecular biology are Type II restriction enzymes, which recognize specific palindromic DNA sequences and cut within or near these sequences to produce cohesive ends. Examples of Type II restriction enzymes include EcoRI, HindIII, and BamHI, each of which recognizes and cuts a specific DNA sequence, producing DNA fragments with predictable cohesive ends.

Applications

Cohesive ends are utilized in various applications beyond DNA cloning, including:

• Genetic Engineering: To insert genes of interest into plasmids or other vectors for expression in host organisms.
• Gene Therapy: To construct vectors carrying therapeutic genes that can be introduced into patient cells.
• Molecular Diagnostics: In the development of assays for the detection of specific DNA sequences associated with pathogens or genetic disorders.

Challenges and Solutions

While cohesive ends facilitate the joining of DNA fragments, they also present challenges, such as re-ligation of the vector without the insertion of the target DNA fragment. To overcome this, molecular biologists often use dephosphorylation of vector DNA to prevent self-ligation, or employ Cloning Vectors with non-compatible cohesive ends for the insertion and vector fragments, ensuring that only fragments with matching ends can ligate.

Conclusion

Cohesive ends are a fundamental concept in molecular biology, enabling the precise and efficient assembly of DNA fragments in various biotechnological and medical applications. The ability to manipulate DNA in this way has revolutionized the fields of genetics, medicine, and biotechnology, leading to significant advancements in our understanding and manipulation of genetic material.

Cohesive end Resources
Need Help Finding a Doctor? Need help finding a doctor or specialist anywhere in the world? Explore our world directory. WikiMD's DocFinder can assist you in locating millions of physicians.	Medical Knowledge Access the latest research - Most recent articles Ongoing trials.