Lecture 3 - Transformation | Genetics (Zoology) by ILLL, DU - Biotechnology Engineering (BT) PDF Download

 Page 1


Transformation 
1 
Institute of Lifelong Learning, University of Delhi 
 
 
 
 
Genetics and Genomics 
Lesson:Transformation 
Lesson Developer: Dr. ShaillyAnand 
College/Dept: Department of Zoology, Deen Dayal 
Upadhyaya College (University of Delhi) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Page 2


Transformation 
1 
Institute of Lifelong Learning, University of Delhi 
 
 
 
 
Genetics and Genomics 
Lesson:Transformation 
Lesson Developer: Dr. ShaillyAnand 
College/Dept: Department of Zoology, Deen Dayal 
Upadhyaya College (University of Delhi) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Transformation 
2 
Institute of Lifelong Learning, University of Delhi 
 
 
 
Table of Contents 
 
Chapter: TRANSFORMATION 
? Introduction  
? Historical background 
? 1928: Frederick Griffith’s transformation experiment 
? 1944: Avery, Macleod and McCarty’s discovery of DNA as 
the genetic material 
? Natural vs Artificial Competence 
? The process of transformation 
? Competent Cells (Induced competency) 
? Growing gram negative bacteria (host cells) in presence 
of magnesium 
? Treating cells with divalent cations 
? Presence of channels on cell surface for DNA uptake 
? DNA binding receptors 
? Transformation Efficiency vs. Transformation Frequency 
? Transformation Efficiency 
? Transformation Frequency 
? Methods of Transformation 
? Heat shock method 
? Electroporation or Electropermeability 
? Applications of Transformation 
? Summary  
? Practice Questions 
? Glossary 
Page 3


Transformation 
1 
Institute of Lifelong Learning, University of Delhi 
 
 
 
 
Genetics and Genomics 
Lesson:Transformation 
Lesson Developer: Dr. ShaillyAnand 
College/Dept: Department of Zoology, Deen Dayal 
Upadhyaya College (University of Delhi) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Transformation 
2 
Institute of Lifelong Learning, University of Delhi 
 
 
 
Table of Contents 
 
Chapter: TRANSFORMATION 
? Introduction  
? Historical background 
? 1928: Frederick Griffith’s transformation experiment 
? 1944: Avery, Macleod and McCarty’s discovery of DNA as 
the genetic material 
? Natural vs Artificial Competence 
? The process of transformation 
? Competent Cells (Induced competency) 
? Growing gram negative bacteria (host cells) in presence 
of magnesium 
? Treating cells with divalent cations 
? Presence of channels on cell surface for DNA uptake 
? DNA binding receptors 
? Transformation Efficiency vs. Transformation Frequency 
? Transformation Efficiency 
? Transformation Frequency 
? Methods of Transformation 
? Heat shock method 
? Electroporation or Electropermeability 
? Applications of Transformation 
? Summary  
? Practice Questions 
? Glossary 
Transformation 
3 
Institute of Lifelong Learning, University of Delhi 
? Answer to the questions 
? References 
 
Introduction 
Transformation literally means ‘a change’. Bacterial transformation can thus be defined as a 
process by which a foreign DNA is taken up by a cell thereby changing its genetic makeup. 
It is one of the three chief ways of recombination in bacteria (conjugation, transformation 
and transduction). The previous chapter discussed the process of conjugation while this 
chapter focuses on transformation especially with reference to bacteria. Transformation 
differs from conjugation in the absence of any direct physical contact between the two cells 
as no sex pilus is formed. Also transformation involves the uptake of naked/ free/ 
exogenous DNA by a cell. Hence the presence of a living donor cell is not a necessity. 
There can be three distinct explanations for the evolution of DNA uptake systems in bacteria 
– (a) for genetic diversity, as gaining traits like antibiotic resistance, virulence or functions 
aiding in metabolism etc can provide a better survival prospect to the host; (b) for DNA 
repair, because DNA of a closely related species can act as a template for repair 
mechanisms in bacterial DNA; and, (c) for food, providing a source of carbon, phosphate 
and nitrogen upon breakdown.Environment is rich in such naked or free DNA as 
disintegration of host body due to death releases the DNA into the environment 
continuously. 
 
Historical Background 
1928: Frederick Griffith’s transformation experiment 
Frederick Griffith, an English microbiologist worked on the pneumonia causing bacteria 
Streptococcus pneumoniae. Based on the presence of the allele for capsule gene, it has two 
strains namely; 
? S (Smooth) strain – Bacteria has a capsule (i.e. is encapsulated), is pathogenic 
(or virulent) and colonies have a smooth appearance. 
Page 4


Transformation 
1 
Institute of Lifelong Learning, University of Delhi 
 
 
 
 
Genetics and Genomics 
Lesson:Transformation 
Lesson Developer: Dr. ShaillyAnand 
College/Dept: Department of Zoology, Deen Dayal 
Upadhyaya College (University of Delhi) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Transformation 
2 
Institute of Lifelong Learning, University of Delhi 
 
 
 
Table of Contents 
 
Chapter: TRANSFORMATION 
? Introduction  
? Historical background 
? 1928: Frederick Griffith’s transformation experiment 
? 1944: Avery, Macleod and McCarty’s discovery of DNA as 
the genetic material 
? Natural vs Artificial Competence 
? The process of transformation 
? Competent Cells (Induced competency) 
? Growing gram negative bacteria (host cells) in presence 
of magnesium 
? Treating cells with divalent cations 
? Presence of channels on cell surface for DNA uptake 
? DNA binding receptors 
? Transformation Efficiency vs. Transformation Frequency 
? Transformation Efficiency 
? Transformation Frequency 
? Methods of Transformation 
? Heat shock method 
? Electroporation or Electropermeability 
? Applications of Transformation 
? Summary  
? Practice Questions 
? Glossary 
Transformation 
3 
Institute of Lifelong Learning, University of Delhi 
? Answer to the questions 
? References 
 
Introduction 
Transformation literally means ‘a change’. Bacterial transformation can thus be defined as a 
process by which a foreign DNA is taken up by a cell thereby changing its genetic makeup. 
It is one of the three chief ways of recombination in bacteria (conjugation, transformation 
and transduction). The previous chapter discussed the process of conjugation while this 
chapter focuses on transformation especially with reference to bacteria. Transformation 
differs from conjugation in the absence of any direct physical contact between the two cells 
as no sex pilus is formed. Also transformation involves the uptake of naked/ free/ 
exogenous DNA by a cell. Hence the presence of a living donor cell is not a necessity. 
There can be three distinct explanations for the evolution of DNA uptake systems in bacteria 
– (a) for genetic diversity, as gaining traits like antibiotic resistance, virulence or functions 
aiding in metabolism etc can provide a better survival prospect to the host; (b) for DNA 
repair, because DNA of a closely related species can act as a template for repair 
mechanisms in bacterial DNA; and, (c) for food, providing a source of carbon, phosphate 
and nitrogen upon breakdown.Environment is rich in such naked or free DNA as 
disintegration of host body due to death releases the DNA into the environment 
continuously. 
 
Historical Background 
1928: Frederick Griffith’s transformation experiment 
Frederick Griffith, an English microbiologist worked on the pneumonia causing bacteria 
Streptococcus pneumoniae. Based on the presence of the allele for capsule gene, it has two 
strains namely; 
? S (Smooth) strain – Bacteria has a capsule (i.e. is encapsulated), is pathogenic 
(or virulent) and colonies have a smooth appearance. 
Transformation 
4 
Institute of Lifelong Learning, University of Delhi 
? R (Rough) strain –Bacteria lacks a capsule, is non-pathogenic (or non- virulent) 
and colonies are rough in appearance. 
 
 
Value Addition: Did You Know?? 
Heading Text: Biographic sketch of Frederick Griffith (1877–1941) 
Body Text:Frederick Griffith (1877–1941), a 
British bacteriologist reported in January 1928 the first 
widely accepted demonstrations of bacterial 
transformation, whereby a bacterium distinctly 
changes its form and function. His main focus in 
research was the epidemiology and pathology of 
bacterial pneumonia.  
He showed that Streptococcus pneumoniae, 
implicated in many cases of lobar pneumonia, could 
transform from one strain into a different strain. The 
observation was attributed to an unidentified 
transforming principle or transforming factor. This was 
later identified as DNA and this experiment is 
popularly known as Griffith's Experiment 
Source:http://en.wikipedia.org/wiki/Frederick_Griffith#mediaviewer/File:Griffithm.
jpgCC 
 
In 1928, he observed that when the non-virulent R-strain of S. pneumoniae was mixed with 
heat killed cells of the virulent S-strain, the former transformed into a pathogenic strain. 
This was reflected by the appearance of symptoms of pneumonia in mice injected with the 
mix of cells. Based on his observation, he concluded that when a S-strain is heat killed, 
some factor from the dead S-strain converted R to S-strain. Since this transformation was 
inherited by subsequent generations, it was thought to be the genetic material and was 
referred to as the transforming principle.  
 
Page 5


Transformation 
1 
Institute of Lifelong Learning, University of Delhi 
 
 
 
 
Genetics and Genomics 
Lesson:Transformation 
Lesson Developer: Dr. ShaillyAnand 
College/Dept: Department of Zoology, Deen Dayal 
Upadhyaya College (University of Delhi) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Transformation 
2 
Institute of Lifelong Learning, University of Delhi 
 
 
 
Table of Contents 
 
Chapter: TRANSFORMATION 
? Introduction  
? Historical background 
? 1928: Frederick Griffith’s transformation experiment 
? 1944: Avery, Macleod and McCarty’s discovery of DNA as 
the genetic material 
? Natural vs Artificial Competence 
? The process of transformation 
? Competent Cells (Induced competency) 
? Growing gram negative bacteria (host cells) in presence 
of magnesium 
? Treating cells with divalent cations 
? Presence of channels on cell surface for DNA uptake 
? DNA binding receptors 
? Transformation Efficiency vs. Transformation Frequency 
? Transformation Efficiency 
? Transformation Frequency 
? Methods of Transformation 
? Heat shock method 
? Electroporation or Electropermeability 
? Applications of Transformation 
? Summary  
? Practice Questions 
? Glossary 
Transformation 
3 
Institute of Lifelong Learning, University of Delhi 
? Answer to the questions 
? References 
 
Introduction 
Transformation literally means ‘a change’. Bacterial transformation can thus be defined as a 
process by which a foreign DNA is taken up by a cell thereby changing its genetic makeup. 
It is one of the three chief ways of recombination in bacteria (conjugation, transformation 
and transduction). The previous chapter discussed the process of conjugation while this 
chapter focuses on transformation especially with reference to bacteria. Transformation 
differs from conjugation in the absence of any direct physical contact between the two cells 
as no sex pilus is formed. Also transformation involves the uptake of naked/ free/ 
exogenous DNA by a cell. Hence the presence of a living donor cell is not a necessity. 
There can be three distinct explanations for the evolution of DNA uptake systems in bacteria 
– (a) for genetic diversity, as gaining traits like antibiotic resistance, virulence or functions 
aiding in metabolism etc can provide a better survival prospect to the host; (b) for DNA 
repair, because DNA of a closely related species can act as a template for repair 
mechanisms in bacterial DNA; and, (c) for food, providing a source of carbon, phosphate 
and nitrogen upon breakdown.Environment is rich in such naked or free DNA as 
disintegration of host body due to death releases the DNA into the environment 
continuously. 
 
Historical Background 
1928: Frederick Griffith’s transformation experiment 
Frederick Griffith, an English microbiologist worked on the pneumonia causing bacteria 
Streptococcus pneumoniae. Based on the presence of the allele for capsule gene, it has two 
strains namely; 
? S (Smooth) strain – Bacteria has a capsule (i.e. is encapsulated), is pathogenic 
(or virulent) and colonies have a smooth appearance. 
Transformation 
4 
Institute of Lifelong Learning, University of Delhi 
? R (Rough) strain –Bacteria lacks a capsule, is non-pathogenic (or non- virulent) 
and colonies are rough in appearance. 
 
 
Value Addition: Did You Know?? 
Heading Text: Biographic sketch of Frederick Griffith (1877–1941) 
Body Text:Frederick Griffith (1877–1941), a 
British bacteriologist reported in January 1928 the first 
widely accepted demonstrations of bacterial 
transformation, whereby a bacterium distinctly 
changes its form and function. His main focus in 
research was the epidemiology and pathology of 
bacterial pneumonia.  
He showed that Streptococcus pneumoniae, 
implicated in many cases of lobar pneumonia, could 
transform from one strain into a different strain. The 
observation was attributed to an unidentified 
transforming principle or transforming factor. This was 
later identified as DNA and this experiment is 
popularly known as Griffith's Experiment 
Source:http://en.wikipedia.org/wiki/Frederick_Griffith#mediaviewer/File:Griffithm.
jpgCC 
 
In 1928, he observed that when the non-virulent R-strain of S. pneumoniae was mixed with 
heat killed cells of the virulent S-strain, the former transformed into a pathogenic strain. 
This was reflected by the appearance of symptoms of pneumonia in mice injected with the 
mix of cells. Based on his observation, he concluded that when a S-strain is heat killed, 
some factor from the dead S-strain converted R to S-strain. Since this transformation was 
inherited by subsequent generations, it was thought to be the genetic material and was 
referred to as the transforming principle.  
 
Transformation 
5 
Institute of Lifelong Learning, University of Delhi 
 
 
Figure 1: Griffith’s transforming principle- S (Smooth) and R (Rough) strains 
of Streptococcus pneumoniae. When injected into mice, the R strain has no effect while the 
S strain causes death of mice. Frederick Griffith heat killed the S strain and mixed it with 
the non-pathogenic R strain.When left for a period of time, R-strain transformed into the 
pathogenic S strain which killed the mice when injected. 
Source: Author