What was Griffith's experiment with Streptococcus pneumoniae?
Frederick Griffith conducted a series of experiments with Streptococcus pneumonia bacteria and mice in 1928 and concluded that the R-strain bacteria must have picked up a "transforming principle" from the heat-killed S bacteria, allowing them to "transform" into smooth-coated bacteria and become virulent.
What did Griffith's experiment show?
The “Griffith's Experiment,” conducted in 1928 by English bacteriologist Frederick Griffith described the conversion of a non-pathogenic pneumococcal bacteria to a virulent strain.17 In this experiment, Griffith mixed the living non-virulent bacteria with a heat inactivated virulent form.
How did Griffith's experiment kill the mice?
In the second stage, Griffith heat-killed the S strain bacteria and injected into mice, but the mice stayed alive. Then, he mixed the heat-killed S and live R strains. This mixture was injected into mice and they died.
How did Griffith kill the s cells?
As part of his experiments, Griffith tried injecting mice with heat-killed S bacteria (that is, S bacteria that had been heated to high temperatures, causing the cells to die). Unsurprisingly, the heat-killed S bacteria did not cause disease in mice.
What was Griffith's experiment and what were the results of it?
As part of his experiments, Griffith tried injecting mice with heat-killed S bacteria (that is, S bacteria that had been heated to high temperatures, causing the cells to die). Unsurprisingly, the heat-killed S bacteria did not cause disease in mice.
What did Frederick Griffith Find out in his experiment?
Frederick Griffith, (born October 3, 1877, Eccleston, Lancashire, England—died 1941, London), British bacteriologist whose 1928 experiment with bacterium was the first to reveal the “transforming principle,” which led to the discovery that DNA acts as the carrier of genetic information.
How does Griffith's experiment prove DNA as genetic material?
He had no idea of that transforming agent. ( Today, we know that the "transforming principle" Griffith observed was the DNA of the III-s strain bacteria. While the bacteria had been killed, the DNA had survived the heating process and was taken up by the II-R strain bacteria.
Why was Griffith'S experiment important?
While trying to find a cure for pneumonia, Griffith made a major scientific discovery. Griffith's famous 1928 experiment showed us that bacteria can distinctly change their function (what they do) and form (how they look). Before his experiment, scientists believed that bacteria were fixed and unchangeable!
What were the main outcomes of the experiments performed by Griffith 1928?
What were the main outcomes of the experiments performed by Griffith (1928)? He found that a mixture of living rough-type and dead smooth-type bacteria killed mice. He found that living smooth-type bacteria killed mice.
Who proved DNA as genetic material?
In 1952, Alfred Hershey and Martha Chase took an effort to find the genetic material in organisms. Their experiments led to an unequivocal proof to DNA as genetic material. Bacteriophages (viruses that affect bacteria) were the key element for Hershey and Chase experiment.
What evidence from Griffith's investigation suggested that there was a transforming principle?
What evidence suggested that there was a transforming principle? When the mice died and Griffith found live S bacteria in blood samples from the dead mice! Griffith concluded that some material must have been transferred from the heat-killed S bacteria to the live R bacteria.
What is Griffith transforming principle?
He observed that something which he called “transforming principle” was getting transferred from heat killed S strain to live R strain which allowed the live R strain to transform into S strain which was highly pathogenic. This phenomenon is known as the transforming principle.
What was Frederick Griffith's hypothesis?
Based on these observations, Griffith hypothesized that a chemical component from the virulent S cells had somehow transformed the R cells into the more virulent S form (Griffith, 1928).
What was transformed in Griffith's experiment?
What was "transformed" in Griffith's experiment? The R bacteria. How did avert and his group identify the transforming principle? Avery and his group added extract enzymes known to break down proteins, the extract still transformed the R bacteria to the S form.
Who discovered gene transfer?
Frederick GriffithThe concept of gene transfer between cells was first demonstrated in bacteria, which are capable of at least four natural forms of genetic exchange. The first mechanism was discovered in 1928 by Frederick Griffith named as transformation in bacterium Streptococcus pneumoniae.
Which was a conclusion of Griffith's work with Streptococcus?
Griffith concluded that the type II-R had been "transformed" into the lethal III-S strain by a "transforming principle" that was somehow part of the dead III-S strain bacteria. Today, we know that the "transforming principle" Griffith observed was the DNA of the III-s strain bacteria.
What was Griffith’s experiment and why was it important?
Griffith’s experiment was the first experiment which suggested that bacteria can transfer genetic information through a process called transformation.
What is the conclusion of Griffith experiment?
The experiment concluded that bacteria are capable of transfering genetic information through transformation.
What was the most significant conclusion of Griffith’s experiments with pneumonia in mice?
The experiment conducted by Griffith found that bacteria are capable of transfering genetic information through transformation.
What did Frederick Griffith want to learn about bacteria?
Frederick Griffith wanted to learn if bacterial transformation was possible.
How did the two types of bacteria used by Griffith differ?
Griffith used two strains of pneumococcus (Streptococcus pneumoniae) bacteria: a type III-S and a type II-R.
1. Explain the Oswald Avery Experiment.
Avery and his colleagues conducted additional research on the virulent S strain of Streptococcus pneumonia. They were aware that the potential carr...
2. What are the characteristics of genetic material?
Any substance that forms the genetic material must fulfil some essential requirements:It must be stable.It should be able to carry and transcribe i...
3. Define Horizontal Gene Transfer.
Horizontal gene transfer (HGT) is the exchange of genetic information between organisms, which includes the spread of antibiotic resistance genes a...
How does S. pneumoniae enter the competent state?
S. pneumoniae enters the competent state under favorable growth conditions during exponential growth , in a process that is governed by quorum sensing [16,70,71]. The rapid increase in cell density leads to an extracellular accumulation of the quorum sensing signal, the competence-stimulating peptide (CSP). Once it exceeds a threshold concentration, it activates the ComD histidine kinase, leading to its autophosphorylation. Upon phospho-transfer, its cognate response regulator, ComE, becomes activated and regulates about 20 early competence ( com) genes [70,72,73]. Among these are two identical copies of comX, which encode alternative sigma factors that activate the transcription of the late com genes [74] ( Fig. 2 ). In total, the CSP-responsive regulon in S. pneumoniae comprises about 120 genes, of which only 22 are necessary for developing natural competence [23,75,76]. This suggests that the majority of the com system is involved in additional cellular processes beyond the machinery required for DNA uptake and recombination [16].
What type of cells were recovered from mice?
Importantly, the newly encapsulated transformed bacteria that were recovered from the hearts of infected dead mice were of serotype I of the heat-killed S cells and not of Type II from which the R cells were originally derived. Notably, Griffith also executed the reverse experiment, that is, mice that were inoculated with a mixture of heat-killed SI cells and living RII pneumococci died and produced living SI cells.
What is the process of natural transformation?
Natural transformation occurs when competent recipient cells take up naked DNA from the environment ( Lorenz and Wackernagel, 1994 ). The idea of a nonheritable exchange of genetic information was first documented in 1928 with work on the pathogen Streptococcus pneumoniae ( Griffith, 1928). Griffith showed that virulence factors from a killed pathogenic strain could “transform” a nonvirulent strain to become virulent as well. Although it was unknown at the time of Griffith's experiment, DNA was determined to be the transforming principle responsible for the change from nonvirulent to virulent that Griffith had documented in his classic experiments (Avery et al., 1944 ).
What is the Fig. 1.4?
Fig. 1.4. Schematic diagram of a typical gene cloning process and the application of the gene cloning. The production of the specific eukaryotic protein derived from that introduced eukaryotic DNA segment proves that DNA is the genetic material in the eukaryotic cells.
What is the phage?
The phage consists of a protein coat surrounding a core of DNA. The phage attaches to the bacterial cell, and the genetic component of the phage enters the bacterial cells. Following infection, the viral genetic component dominates the cellular machinery of the host cells and leads to viral reproduction.
What is the genetic material of bacteria?
DNA Is the Genetic Material for Bacteria. Griffith's work led to further research of the transformation phenomenon. In 1944, Oswald Avery, Colin MacLeod, and Maclyn McCarty published what is now considered a classic paper in the field of molecular genetics.
What was the transforming principle of Griffith's experiment?
Although it was unknown at the time of Griffith's experiment, DNA was determined to be the transforming principle responsible for the change from nonvirulent to virulent that Griffith had documented in his classic experiments (Avery et al., 1944 ).
Griffith Experiment: An Introduction
It may come as a surprise that less than a century ago, even the most educated members of the scientific community were unaware that DNA was a hereditary material.
Who was Frederick Griffith?
The "Griffith's Experiment," carried out by English bacteriologist Frederick Griffith in 1928, described the transformation of a non-pathogenic pneumococcal bacteria into a virulent strain.
R Strain And S Strain Bacteria
Streptococcus pneumonia comes in several types or strains. Griffith chose two different strains for his experiment.
Impact of The Griffith Experiment
One of the characteristics of hereditary material is a changing phenotype. Griffith referred to the phenotypic-changing factor as the transforming principle.
Conclusion
Griffith's ultimate goal was to find a way to cure pneumonia. Griffith inoculated mice with various strains of pneumococci to see if they would infect and eventually kill the mice. Griffith concluded that heat-killed virulent bacteria transformed living, non-virulent bacteria into virulent bacteria.
What type of bacteria did Griffith use?
Griffith used two strains of pneumococcus ( Streptococcus pneumoniae) bacteria which infect mice – a type III-S (smooth) which was virulent, and a type II-R (rough) strain which was nonvirulent.
What was the transforming principle of the III-S strain?
Today, we know that the "transforming principle" Griffith observed was the DNA of the III-s strain bacteria. While the bacteria had been killed, ...
What did Griffith's experiment show about bacteria?
In this experiment, bacteria from the III-S strain were killed by heat, and their remains were added to II-R strain bacteria.
Which strain of bacteria has the genes that form the smooth protective polysaccharide capsule?
While the bacteria had been killed, the DNA had survived the heating process and was taken up by the II-R strain bacteria. The III-S strain DNA contains the genes that form the smooth protective polysaccharide capsule.
What was the first experiment that showed that bacteria are capable of transferring genetic information through a process known as transformation?
Griffith's experiment, reported in 1928 by Frederick Griffith, was the first experiment suggesting that bacteria are capable of transferring genetic information through a process known as transformation. Griffith's findings were followed by research in the late 1930s and early 40s that isolated DNA as the material that communicated this genetic ...
What was Griffith's research?
Griffith's findings were followed by research in the late 1930s and early 40s that isolated DNA as the material that communicated this genetic information. Pneumonia was a serious cause of death in the wake of the post-WWI Spanish influenza pandemic, and Griffith was studying the possibility of creating a vaccine.
Did You Know?
Other processes by which exogenous genetic material is taken up by a cell include conjugation (transfer of DNA between two bacterial cells that are in direct contact) and transduction (injection of viral DNA by a bacteriophage into the host bacterial cell).
How did Type III S heat kill mice?
The blood showed no presence of the inoculated cells. Type III S heat-killed bacteria. When the virulent strain was rendered avirulent by heating and killing it (heat-killed), and then injected into the mice, the strain did not show virulence, and was eliminated by the host’s immune system; hence, the mice survived.
What did Frederick Griffith study?
The post-World War I Spanish influenza pandemic influenced Frederick Griffith to study the epidemiology and pathology of bacterial pneumonia in order to attempt creating a successful vaccine. Hence, he carried out experiments, where he injected mice with strains of virulent and avirulent Streptococcus pneumoniae. The experiment he reported in 1928, gave the first description of the phenomenon of transformation, where one bacterial strain could change into the other strain, and this activity was linked to an unidentified element called the transforming factor or transforming principle.
What is the state of being able to take up exogenous DNA called?
Transformation is a stable genetic change brought about by the uptake of naked DNA, and the state of being able to take up exogenous DNA is called competence. They occur in two forms―natural and artificial.
Why is gene expression carried out in laboratories?
It is carried out in laboratories in order to carry out gene expression studies. To impart competence, the cells are incubated in a solution containing divalent cations (calcium chloride) under cold conditions , and then, exposed to intermittent pulses of heat. The concentration of the solution depends on the protein and liposaccharide content of the membrane, and the intensity of the heat pulses varies according to the time duration of the pulses, i.e., high intensity pulses should be for very short periods; whereas, low intensity pulses can be for longer durations.
How does DNA get into Gram negative bacteria?
Gram-negative bacteria show the presence of an extra membrane, hence, for DNA to be taken up, a channel is formed on the outer membrane by secretins. The uptake of a DNA fragment is generally not specific to its sequence; however, in some bacterial species, it has been seen that the presence of certain DNA sequences facilitate and enhance efficient uptake of the genetic material.
What type of bacteria did Griffith inoculate mice with?
While injecting the mice with these bacteria, Griffith devised four sets of inoculation that are as follows: Type III S bacteria. When the mice were inoculated, the bacterial virulence was exhibited, causing pneumonia, and this eventually led to the death of the mice.
How many batches of phage were produced?
To establish whether the phage injected DNA or protein into host bacteria, Hershey and Chase prepared two different batches of phage. In each batch, the phage were produced in the presence of a specific radioactive element, which was incorporated into the macromolecules (DNA and protein) that made up the phage.
Why were the cultures blended and centrifuged?
The cultures were blended and centrifuged to separate the phage from the bacteria.
How are phages used in bacteria?
Each batch of phage was used to infect a different culture of bacteria. After infection had taken place, each culture was whirled in a blender, removing any remaining phage and phage parts from the outside of the bacterial cells. Finally, the cultures were centrifuged, or spun at high speeds, to separate the bacteria from the phage debris.
Why are S bacteria smooth?
The smooth appearance was due to a polysaccharide, or sugar-based, coat produced by the bacteria. This coat protected the S bacteria from the mouse immune system, making them virulent (capable of causing disease).
What is the difference between DNA and proteins?
Scientists first thought that proteins, which are found in chromosomes along with DNA, would turn out to be the sought-after genetic material. Proteins were known to have diverse amino acid sequences, while DNA was thought to be a boring, repetitive polymer, due in part to an incorrect (but popular) model of its structure and composition.
Why do zygote twins have two eggs?
It happens, because normally there is only one egg at the time of ovulation in the ovarian duct. And if a sperm is present there is more than enough of spermatozoids. So one lucky sperm fertilizes one egg. This way an zygote is produced which later becomes embryo and eventually a baby.#N#But in some cases, there is two or even more eggs in the ovarian duct, and as we know there are hundreds of sperms, both can get fertilized. In this case two different zygotes form, hence the name "dizygotic" twins. In more simple way, it is like getting pregnant twice, when female body gives two eggs that can be fertilized. And different eggs have different sets of DNA (because of myosis, crossover and other things). So dizygotic twins are related as much as simple brothers (or sisters).
What is the role of DNA in heredity?
Our modern understanding of DNA's role in heredity has led to a variety of practical applications, including forensic analysis, paternity testing, and genetic screening. Thanks to these wide-ranging uses, today many people have at least a basic awareness of DNA.
