Lecture 5 - Uses of Transposons & Eukaryotic Viruses | Genetics (Zoology) by ILLL, DU - Biotechnology Engineering (BT) PDF Download

 Page 1


 Uses of Transposable Elements & Eukaryotic Viruses  
 
Institute of Lifelong Learning, University of Delhi  Page 1 
 
 
                                 
 
                                         NME-Zoology 
                 Subject: Genetics and Genomics 
        Lesson: Uses of Transposons & Eukaryotic Viruses 
                 Lesson Developer: Dr. Shailly Anand 
1
 
                                                Dr. Jaya Malhotra
2 
         College/Dept: Deen Dayal Upadhyaya College
1
,  
                                   Hansraj College
2 
 
 
 
 
 
 
 
 
 
Page 2


 Uses of Transposable Elements & Eukaryotic Viruses  
 
Institute of Lifelong Learning, University of Delhi  Page 1 
 
 
                                 
 
                                         NME-Zoology 
                 Subject: Genetics and Genomics 
        Lesson: Uses of Transposons & Eukaryotic Viruses 
                 Lesson Developer: Dr. Shailly Anand 
1
 
                                                Dr. Jaya Malhotra
2 
         College/Dept: Deen Dayal Upadhyaya College
1
,  
                                   Hansraj College
2 
 
 
 
 
 
 
 
 
 
 Uses of Transposable Elements & Eukaryotic Viruses  
 
Institute of Lifelong Learning, University of Delhi  Page 2 
 
 
 
Table of Contents 
? Uses of Transposons 
? IS elements mediates recombination 
? Formation of conjugative R plasmids 
? Insertion mutations 
? Chromosome breakage and rearrangement 
? Genetic transformation 
? Eukaryotic Viruses: An introduction 
? Classification of Eukaryotic Viruses 
? DNA & RNA viruses 
? Icosahedral & Helical Viruses 
? Naked & Enveloped Viruses 
? Life Cycle of Eukaryotic Viruses 
? Retroviruses: Special RNA Viruses 
? Gene Composition 
? Growth Cycle of Retroviruses 
? Retroviruses & Oncogenes 
? Summary 
? Glossary 
? Practice Questions 
? Answer to the Questions 
? References 
 
 
 
 
Page 3


 Uses of Transposable Elements & Eukaryotic Viruses  
 
Institute of Lifelong Learning, University of Delhi  Page 1 
 
 
                                 
 
                                         NME-Zoology 
                 Subject: Genetics and Genomics 
        Lesson: Uses of Transposons & Eukaryotic Viruses 
                 Lesson Developer: Dr. Shailly Anand 
1
 
                                                Dr. Jaya Malhotra
2 
         College/Dept: Deen Dayal Upadhyaya College
1
,  
                                   Hansraj College
2 
 
 
 
 
 
 
 
 
 
 Uses of Transposable Elements & Eukaryotic Viruses  
 
Institute of Lifelong Learning, University of Delhi  Page 2 
 
 
 
Table of Contents 
? Uses of Transposons 
? IS elements mediates recombination 
? Formation of conjugative R plasmids 
? Insertion mutations 
? Chromosome breakage and rearrangement 
? Genetic transformation 
? Eukaryotic Viruses: An introduction 
? Classification of Eukaryotic Viruses 
? DNA & RNA viruses 
? Icosahedral & Helical Viruses 
? Naked & Enveloped Viruses 
? Life Cycle of Eukaryotic Viruses 
? Retroviruses: Special RNA Viruses 
? Gene Composition 
? Growth Cycle of Retroviruses 
? Retroviruses & Oncogenes 
? Summary 
? Glossary 
? Practice Questions 
? Answer to the Questions 
? References 
 
 
 
 
 Uses of Transposable Elements & Eukaryotic Viruses  
 
Institute of Lifelong Learning, University of Delhi  Page 3 
 
 
 
Uses of Transposons 
For many years scientists could not answer the reason behind the presence of transposons 
in the genome. Without any significant contribution in the genome they should have been 
eliminated during the course of evolution. On the contrary, transposons are prevalent in 
almost all kinds of living organisms. They have served as nature’s genetic tool for 
manipulating and modifying the genomic organization of a particular genome. Some of the 
uses of transposons in the light of evolution have been listed below.  
 
IS elements mediates recombination 
Several copies of single type of IS elements can be present in a bacterial genome. These 
can be distributed in plasmid as well as the chromosome. When similar type of IS elements 
are present both in the plasmid and the chromosome they can undergo recombination to 
form a single bigger molecule by the integration of the plasmid in the chromosome. This 
 
Page 4


 Uses of Transposable Elements & Eukaryotic Viruses  
 
Institute of Lifelong Learning, University of Delhi  Page 1 
 
 
                                 
 
                                         NME-Zoology 
                 Subject: Genetics and Genomics 
        Lesson: Uses of Transposons & Eukaryotic Viruses 
                 Lesson Developer: Dr. Shailly Anand 
1
 
                                                Dr. Jaya Malhotra
2 
         College/Dept: Deen Dayal Upadhyaya College
1
,  
                                   Hansraj College
2 
 
 
 
 
 
 
 
 
 
 Uses of Transposable Elements & Eukaryotic Viruses  
 
Institute of Lifelong Learning, University of Delhi  Page 2 
 
 
 
Table of Contents 
? Uses of Transposons 
? IS elements mediates recombination 
? Formation of conjugative R plasmids 
? Insertion mutations 
? Chromosome breakage and rearrangement 
? Genetic transformation 
? Eukaryotic Viruses: An introduction 
? Classification of Eukaryotic Viruses 
? DNA & RNA viruses 
? Icosahedral & Helical Viruses 
? Naked & Enveloped Viruses 
? Life Cycle of Eukaryotic Viruses 
? Retroviruses: Special RNA Viruses 
? Gene Composition 
? Growth Cycle of Retroviruses 
? Retroviruses & Oncogenes 
? Summary 
? Glossary 
? Practice Questions 
? Answer to the Questions 
? References 
 
 
 
 
 Uses of Transposable Elements & Eukaryotic Viruses  
 
Institute of Lifelong Learning, University of Delhi  Page 3 
 
 
 
Uses of Transposons 
For many years scientists could not answer the reason behind the presence of transposons 
in the genome. Without any significant contribution in the genome they should have been 
eliminated during the course of evolution. On the contrary, transposons are prevalent in 
almost all kinds of living organisms. They have served as nature’s genetic tool for 
manipulating and modifying the genomic organization of a particular genome. Some of the 
uses of transposons in the light of evolution have been listed below.  
 
IS elements mediates recombination 
Several copies of single type of IS elements can be present in a bacterial genome. These 
can be distributed in plasmid as well as the chromosome. When similar type of IS elements 
are present both in the plasmid and the chromosome they can undergo recombination to 
form a single bigger molecule by the integration of the plasmid in the chromosome. This 
 
 Uses of Transposable Elements & Eukaryotic Viruses  
 
Institute of Lifelong Learning, University of Delhi  Page 4 
 
Figure 1. Integration of F factor into the bacterial chromosome is 
mediated by transposon recombination.  
Source: Author (Malhotra, J.) 
 
bacterium becomes an Hfr bacterial strain and its genome can be transferred to other 
bacterial strains during conjugation. Hence the genes present on the plasmid can be 
transferred to other bacterial strains with the help of IS elements (Fig. 1). 
Formation of conjugative R plasmids 
Another important characteristic of the IS elements that are present on the plasmids is the 
formation of conjugative R plasmids from the non conjugative types (Fig. 2). The basic 
structure of a conjugative R plasmid has two components, one is the RTF (resistance 
transfer factor) that helps in transfer of the other component; R determinant. The R 
determinant contains genes that confer resistance to antibiotics or other antibacterial drugs; 
therefore such plasmids are termed as R plasmids. The RTF region of different plasmids 
bears similarity while the R determinant is more diverse in nature and can be flanked by IS 
elements. As already explained in the above paragraph the homologous IS elements can 
mediate transposition of the R determinant from one plasmid to another. Transposition can 
occur irrespective of their orientation.  
Page 5


 Uses of Transposable Elements & Eukaryotic Viruses  
 
Institute of Lifelong Learning, University of Delhi  Page 1 
 
 
                                 
 
                                         NME-Zoology 
                 Subject: Genetics and Genomics 
        Lesson: Uses of Transposons & Eukaryotic Viruses 
                 Lesson Developer: Dr. Shailly Anand 
1
 
                                                Dr. Jaya Malhotra
2 
         College/Dept: Deen Dayal Upadhyaya College
1
,  
                                   Hansraj College
2 
 
 
 
 
 
 
 
 
 
 Uses of Transposable Elements & Eukaryotic Viruses  
 
Institute of Lifelong Learning, University of Delhi  Page 2 
 
 
 
Table of Contents 
? Uses of Transposons 
? IS elements mediates recombination 
? Formation of conjugative R plasmids 
? Insertion mutations 
? Chromosome breakage and rearrangement 
? Genetic transformation 
? Eukaryotic Viruses: An introduction 
? Classification of Eukaryotic Viruses 
? DNA & RNA viruses 
? Icosahedral & Helical Viruses 
? Naked & Enveloped Viruses 
? Life Cycle of Eukaryotic Viruses 
? Retroviruses: Special RNA Viruses 
? Gene Composition 
? Growth Cycle of Retroviruses 
? Retroviruses & Oncogenes 
? Summary 
? Glossary 
? Practice Questions 
? Answer to the Questions 
? References 
 
 
 
 
 Uses of Transposable Elements & Eukaryotic Viruses  
 
Institute of Lifelong Learning, University of Delhi  Page 3 
 
 
 
Uses of Transposons 
For many years scientists could not answer the reason behind the presence of transposons 
in the genome. Without any significant contribution in the genome they should have been 
eliminated during the course of evolution. On the contrary, transposons are prevalent in 
almost all kinds of living organisms. They have served as nature’s genetic tool for 
manipulating and modifying the genomic organization of a particular genome. Some of the 
uses of transposons in the light of evolution have been listed below.  
 
IS elements mediates recombination 
Several copies of single type of IS elements can be present in a bacterial genome. These 
can be distributed in plasmid as well as the chromosome. When similar type of IS elements 
are present both in the plasmid and the chromosome they can undergo recombination to 
form a single bigger molecule by the integration of the plasmid in the chromosome. This 
 
 Uses of Transposable Elements & Eukaryotic Viruses  
 
Institute of Lifelong Learning, University of Delhi  Page 4 
 
Figure 1. Integration of F factor into the bacterial chromosome is 
mediated by transposon recombination.  
Source: Author (Malhotra, J.) 
 
bacterium becomes an Hfr bacterial strain and its genome can be transferred to other 
bacterial strains during conjugation. Hence the genes present on the plasmid can be 
transferred to other bacterial strains with the help of IS elements (Fig. 1). 
Formation of conjugative R plasmids 
Another important characteristic of the IS elements that are present on the plasmids is the 
formation of conjugative R plasmids from the non conjugative types (Fig. 2). The basic 
structure of a conjugative R plasmid has two components, one is the RTF (resistance 
transfer factor) that helps in transfer of the other component; R determinant. The R 
determinant contains genes that confer resistance to antibiotics or other antibacterial drugs; 
therefore such plasmids are termed as R plasmids. The RTF region of different plasmids 
bears similarity while the R determinant is more diverse in nature and can be flanked by IS 
elements. As already explained in the above paragraph the homologous IS elements can 
mediate transposition of the R determinant from one plasmid to another. Transposition can 
occur irrespective of their orientation.  
 Uses of Transposable Elements & Eukaryotic Viruses  
 
Institute of Lifelong Learning, University of Delhi  Page 5 
 
 
Figure 2. A conjugative plasmid can be transformed into conjugative 
R plasmid by recombination with a non-conjugative R plasmid.  
 Source: Author (Malhotra, J) 
This way of transfer of the resistance genes to other strains of bacteria have been a fast 
vehicle for evolution. It is of great concern in medical science as drug resistant bacterial 
strains are rapidly evolving and making the less virulent bacterial strains gain resistance. 
For instance, E. coli R plasmids have been transferred to different genera like Salmonella, 
Hemophilus to name a few. Because of the above reason, antibiotics should only be 
administered for serious bacterial infections and not for slight infections.