"DNA" is actually an abbreviation of the molecule's full name, deoxyribonucleic acid.

DNA is a molecule that is essential for all life on earth. All DNA, whether it comes from insects, plants, bacteria, or humans, has the same general structure. The fact that all organisms contain DNA is strong support for the theory that all life is derived from a common ancestor.

In some ways, DNA is like the assembly instructions for a living being. The components of DNA, known as genes, determine specific characteristics such the colour of our eyes, the length of our nose, and so on.

But while genes are the supervisors who give the orders, proteins are the workers who actually do the building. Proteins are complex molecules composed of many subunits known as amino acids. The characteristics of each protein are determined by the number and order of its amino acids, which in turn are determined by the instructions contained in the cell's DNA.

When we speak of DNA, the first image that comes to mind is that of two snakes, intertwined and connected to each other through a series of lines, or else that of a long chain of coloured beads. The snakes are i Read More

"DNA" is actually an abbreviation of the molecule's full name, deoxyribonucleic acid.

DNA is a molecule that is essential for all life on earth. All DNA, whether it comes from insects, plants, bacteria, or humans, has the same general structure. The fact that all organisms contain DNA is strong support for the theory that all life is derived from a common ancestor.

In some ways, DNA is like the assembly instructions for a living being. The components of DNA, known as genes, determine specific characteristics such the colour of our eyes, the length of our nose, and so on.

But while genes are the supervisors who give the orders, proteins are the workers who actually do the building. Proteins are complex molecules composed of many subunits known as amino acids. The characteristics of each protein are determined by the number and order of its amino acids, which in turn are determined by the instructions contained in the cell's DNA.

When we speak of DNA, the first image that comes to mind is that of two snakes, intertwined and connected to each other through a series of lines, or else that of a long chain of coloured beads. The snakes are in fact the two nucleotide chains that constitue DNA and the lines between them are true chemical bonds. The nucleotides are always made up of three parts, a sugar (S), a phosphate group (P) and a base (B). Nucleotides can only be differentiated from one another by their bases because the other two parts, the sugar and the phosphate group, are identical for all nucleotides. Four different bases exist, often associated with the letter A, T, C, and G.

To form a chain, the nucleotides bind to one another through the sugars and phosphate groups. Two chains can be linked together when the bases bind to one another. The A always links with the T and the C always links with the G. When the chains of nucleotides are finally long enough, the DNA begins to fold over onto itself and take on its characteristic snake-like appearance.


© Armand-Frappier Museum, 2008. All rights reserved.

RNA is the blueprint for protein production in all organisms, bridging the gap between DNA and proteins. As its name (ribonucleic acid) indicates, its structure is very similar to that of DNA – in fact, DNA acts as the model for RNA.

The first step in building a protein is the transformation of DNA into RNA, in much the same way that a book is translated from one language to another.

There are three structural differences between DNA and RNA, indicated in the following table: Characteristic DNA RNA Name of the sugar Deoxyribose
( the "D" in DNA) Ribose
( the "R" in RNA) Names of the four bases A (adenine) A (adenine) Read More

RNA is the blueprint for protein production in all organisms, bridging the gap between DNA and proteins. As its name (ribonucleic acid) indicates, its structure is very similar to that of DNA – in fact, DNA acts as the model for RNA.

The first step in building a protein is the transformation of DNA into RNA, in much the same way that a book is translated from one language to another.

There are three structural differences between DNA and RNA, indicated in the following table:

Characteristic DNA RNA
Name of the sugar Deoxyribose
( the "D" in DNA)
Ribose
( the "R" in RNA)
Names of the four bases A (adenine) A (adenine)
T (thymine) U (uracil)
C (cytosine) C (cytosine)
G (guanine) G (guanine)
Number of chains 2 1

© Armand-Frappier Museum, 2008. All rights reserved.

DNA, RNA, proteins…what are they, anyway?

Armand-Frappier Museum

© Armand-Frappier Museum, 2008. All rights reserved.


In this photograph, we can see the DNA bands that have migrated in an agarose gel.

Photo : Nicole Catellier

© Nicole Catellier, Cinémanima inc.


The 3-letter abbreviations represent the twenty amino acids. The STOPs give the signal that the protein that is being produced is, in fact, finished. Despite the many repetitions that you can see, please note that the esssential part, the twenty amino acids, is there !

Armand-Frappier Museum

© Armand-Frappier Museum, 2008. All rights reserved.


One form of diabetes is due to a physiological malfunction, namely the inadequate production of the hormone known as insulin. Insulin allows the body's cells to absorb glucose, which they use as food. Diabetics often must receive insulin injections. Today, the insulin which so many diabetics need is produced in large quantities by microorganisms; this type of insulin is known as recombinant insulin. Prior to the use of microorganisms, insulin similar to human insulin was obtained from dogs, pigs, and cows and subsequently purified. This technique is still used today.

As the number of cases of diabetes continued to increase (currently, more than two million Canadians are diabetic), the need to find a way to produce large quantities of insulin inexpensively also grew. Genetic engineering techniques harness microorganisms for this purpose. Since 1983, insulin has been produced commercially on a large scale using the E. coli bacterium, and in 1987, a process based on the yeast Saccharomyces cerevisiae was introduced. Thanks to these advances, diabetics can lead normal lives by injecting small quantities of this hormone.

One form of diabetes is due to a physiological malfunction, namely the inadequate production of the hormone known as insulin. Insulin allows the body's cells to absorb glucose, which they use as food. Diabetics often must receive insulin injections. Today, the insulin which so many diabetics need is produced in large quantities by microorganisms; this type of insulin is known as recombinant insulin. Prior to the use of microorganisms, insulin similar to human insulin was obtained from dogs, pigs, and cows and subsequently purified. This technique is still used today.

As the number of cases of diabetes continued to increase (currently, more than two million Canadians are diabetic), the need to find a way to produce large quantities of insulin inexpensively also grew. Genetic engineering techniques harness microorganisms for this purpose. Since 1983, insulin has been produced commercially on a large scale using the E. coli bacterium, and in 1987, a process based on the yeast Saccharomyces cerevisiae was introduced. Thanks to these advances, diabetics can lead normal lives by injecting small quantities of this hormone.


© Armand-Frappier Museum, 2008. All rights reserved.

How do they actually make insulin?

Armand-Frappier Museum

© Armand-Frappier Museum


The insulin-production process is the same regardless of whether yeast or bacteria are used. First, the gene (a segment of DNA strand) which controls the production of human insulin is inserted into the microorganism. The microorganism, believing the hormone necessary for its survival, produces insulin which is subsequently collected, purified and marketed.

A first!
Insulin production was the first industrial application of this technique in which a bacterium possessing a human gene was used to produce a molecule for human use.

The discovery of insulin: Almost as Canadian as maple syrup!
Did you know that insulin was first isolated, from dogs, in 1922 by four Canadians at the University of Toronto? The insulin was given to a young 14-year-old diabetic named Leonard Thompson, and saved his life! The following year, two of the researchers, Banting and Macleod, received the Nobel Prize. This aggravated tensions which had developed in the group by then, despite the fact that the Nobel laureates shared the prize with the two other researchers, Best and Collip.

Structure of insulin Read More

The insulin-production process is the same regardless of whether yeast or bacteria are used. First, the gene (a segment of DNA strand) which controls the production of human insulin is inserted into the microorganism. The microorganism, believing the hormone necessary for its survival, produces insulin which is subsequently collected, purified and marketed.

A first!
Insulin production was the first industrial application of this technique in which a bacterium possessing a human gene was used to produce a molecule for human use.

The discovery of insulin: Almost as Canadian as maple syrup!
Did you know that insulin was first isolated, from dogs, in 1922 by four Canadians at the University of Toronto? The insulin was given to a young 14-year-old diabetic named Leonard Thompson, and saved his life! The following year, two of the researchers, Banting and Macleod, received the Nobel Prize. This aggravated tensions which had developed in the group by then, despite the fact that the Nobel laureates shared the prize with the two other researchers, Best and Collip.

Structure of insulin
Insulin is composed of two subunits (two chains named A and B) connected to each other by chemical bonds known as disulphide bridges. Note that because the chains are formed of amino acids, insulin is in fact a protein.

What about proinsulin?
The body also produces proinsulin, a precursor of insulin. Because insulin is made up of two chains, the cells must ensure that the chains are properly oriented to each other. The most practical way of making sure that both chains maintain the proper physical relation to each other is to connect them. This connection phase, proinsulin, is made up of two chains (A and B) connected to a third chain known as Peptide C. When proinsulin folds up, bonds form between chains A and B, and Peptide C, which connected them, is removed, yielding active insulin.

How do companies that produce insulin do it?
The first attempts to produce insulin with microorganisms attempted to produce chains A and B separately and connect them chemically. Studies of proinsulin revealed that the body has a much better way of doing things. This method was borrowed, and applied in the microorganisms that produce insulin. Today, yeasts and bacteria produce proinsulin, and Peptide C (which connects chains A and B) is eliminated, just as in humans. That’s all there is to it!


© Armand-Frappier Museum, 2008. All rights reserved.

Hepatitis B is a liver disease caused by HBV (hepatitis B virus). The vaccine developed to prevent infection by this virus consists of little bits of HBV that help the body defend itself against the whole virus. Production of this vaccine consists of producing HBV fragments... a case made to order for microorganisms!

The first hepatitis B vaccine consisted of virus fragments, isolated from sick individuals' blood, likely to be recognized by the body's defences. When administered to healthy people, these fragments allowed to the body to rapidly recognize the entire virus and eliminate it before it could cause infection. But this vaccination technique was not without its hazards. Despite purification procedures, a complete virus sometimes contaminated the vaccine resulting in a healthy person contracting the very disease the vaccine was meant to prevent! In addition, the use of infected individuals as the source of the vaccine presented practical difficulties. The development of a microorganism-based process to produce virus fragments was thus a welcome innovation.

How is the hepatitis B vaccine produced?
Today, the yeast Saccharomyces Read More

Hepatitis B is a liver disease caused by HBV (hepatitis B virus). The vaccine developed to prevent infection by this virus consists of little bits of HBV that help the body defend itself against the whole virus. Production of this vaccine consists of producing HBV fragments... a case made to order for microorganisms!

The first hepatitis B vaccine consisted of virus fragments, isolated from sick individuals' blood, likely to be recognized by the body's defences. When administered to healthy people, these fragments allowed to the body to rapidly recognize the entire virus and eliminate it before it could cause infection. But this vaccination technique was not without its hazards. Despite purification procedures, a complete virus sometimes contaminated the vaccine resulting in a healthy person contracting the very disease the vaccine was meant to prevent! In addition, the use of infected individuals as the source of the vaccine presented practical difficulties. The development of a microorganism-based process to produce virus fragments was thus a welcome innovation.

How is the hepatitis B vaccine produced?
Today, the yeast Saccharomyces cerevisiae is used to produce hepatitis B vaccine. The gene (a segment of DNA strand) which controls the production of small HBV fragments is first inserted into the microorganism. The yeast then produces virus fragments which are subsequently collected, purified and used as a vaccine. Use of HBV-derived DNA segments eliminates the whole virus from the production process and reduces the risk of contamination to zero.


© Armand-Frappier Museum, 2008. All rights reserved.

Illustration representing the hepatitus B virus vaccine produced through genetic engineering.

Illustration Nicole Catellier, Cinémanima inc.

© Cinémanima inc.


ndustry is always on the lookout for new ways to improve production. Dairy producers were therefore very interested in the discovery of somatotrophin, a naturally occurring hormone that controls milk production in cows. The ability of somatotrophin injections to considerably increase milk production was rapidly confirmed. Today, genetically modified bacteria are used to produce the somatotrophin that is administered to milk cows.

Russian researchers were the first to isolate somatotrophin, also known as BST (bovine somatotrophin), extracting it from the cow hypophysis, a gland situated at the base of the brain. In England, attempts were made to apply this knowledge during World War II, when milk shortages were severe. But at that time, it took 20 hypophyses (and therefore, 20 dead cows) to obtain enough hormone for one cow for one day!

Thanks to genetic engineering, somatotrophin can now be produced using the bacterium E. coli.

ndustry is always on the lookout for new ways to improve production. Dairy producers were therefore very interested in the discovery of somatotrophin, a naturally occurring hormone that controls milk production in cows. The ability of somatotrophin injections to considerably increase milk production was rapidly confirmed. Today, genetically modified bacteria are used to produce the somatotrophin that is administered to milk cows.

Russian researchers were the first to isolate somatotrophin, also known as BST (bovine somatotrophin), extracting it from the cow hypophysis, a gland situated at the base of the brain. In England, attempts were made to apply this knowledge during World War II, when milk shortages were severe. But at that time, it took 20 hypophyses (and therefore, 20 dead cows) to obtain enough hormone for one cow for one day!

Thanks to genetic engineering, somatotrophin can now be produced using the bacterium E. coli.


© Armand-Frappier Museum, 2008. All rights reserved.

Production of somatotrophine

Illustration Nicole Catellier, Cinémanima inc.

© Cinémanima inc.


Somatotrophin production
The gene (a segment of DNA strand) responsible for the production of somatotrophin in cows is isolated and then inserted into E. coli. The transformed bacteria produce somatotrophin, believing this hormone to be necessary for their survival. After collection and purification, the hormone is ready to be administered to cows.

The consumption of bovine somatotrophin poses no risks to humans
Somatotrophin also stimulates growth, which explains its other name, growth hormone. Because humans also secrete a growth hormone (HST, human somatotrophin), there was some fear that bovine somatotrophin would have effects on humans. However, the two hormones are quite different and bovine somatotrophin produces no effects in humans. Somatotrophin is degraded by the human digestive system. The level of somatotrophin found in the milk of cows that have received it is identical to that in milk from other cows. 90 % of somatotrophin is destroyed during the pasteurisation of milk.

Somatotrophin production
The gene (a segment of DNA strand) responsible for the production of somatotrophin in cows is isolated and then inserted into E. coli. The transformed bacteria produce somatotrophin, believing this hormone to be necessary for their survival. After collection and purification, the hormone is ready to be administered to cows.

The consumption of bovine somatotrophin poses no risks to humans
Somatotrophin also stimulates growth, which explains its other name, growth hormone. Because humans also secrete a growth hormone (HST, human somatotrophin), there was some fear that bovine somatotrophin would have effects on humans. However, the two hormones are quite different and bovine somatotrophin produces no effects in humans.

  • Somatotrophin is degraded by the human digestive system.
  • The level of somatotrophin found in the milk of cows that have received it is identical to that in milk from other cows.
  • 90 % of somatotrophin is destroyed during the pasteurisation of milk.

© Armand-Frappier Museum, 2008. All rights reserved.

Agriculture began some 10,000 years ago, when humans first domesticated certain plants. Through hybridization and selection, farmers have developed a wide variety of plants with specific characteristics. The development of such plants, and the use of chemical fertilizers, herbicides and pesticides, have contributed to the Green Revolution that began in the late 1940s. However, every revolution has its limits. . . will this one hold the key to feeding continuously growing populations?

Attempts to improve crop production through traditional means face a major obstacle: the species barrier. But this barrier disappears in genetic engineering, in which a gene that controls a certain characteristic in one species (bacteria, plants, mammals and even humans) is transferred into another species' genome and a whole plant generated from the transformed cells. A common example is the use of the soil bacterium Agrobacterium tumefaciens. Transgenic plants hold great promise for the future of sustainable agriculture, but it must first be demonstrated that this technology poses no new health or environmental hazards.

What are the possible applications of this Read More

Agriculture began some 10,000 years ago, when humans first domesticated certain plants. Through hybridization and selection, farmers have developed a wide variety of plants with specific characteristics. The development of such plants, and the use of chemical fertilizers, herbicides and pesticides, have contributed to the Green Revolution that began in the late 1940s. However, every revolution has its limits. . . will this one hold the key to feeding continuously growing populations?

Attempts to improve crop production through traditional means face a major obstacle: the species barrier. But this barrier disappears in genetic engineering, in which a gene that controls a certain characteristic in one species (bacteria, plants, mammals and even humans) is transferred into another species' genome and a whole plant generated from the transformed cells. A common example is the use of the soil bacterium Agrobacterium tumefaciens. Transgenic plants hold great promise for the future of sustainable agriculture, but it must first be demonstrated that this technology poses no new health or environmental hazards.

What are the possible applications of this technology?
In northern climates such as ours, where the growing season is very short, the development of cold-resistant plants would allow the cultivation of new varieties and the extension of agriculture to regions of Quebec currently considered unsuitable for agriculture. Increasing the tolerated temperature range by just a few degrees would extend the growing season by several weeks.

Another benefit is the potential reduction of herbicide and pesticide use. For example, the bacterium Bacillus thuringiensis (Bt) produces a protein that is toxic to the larvae of crop pests. Using genetic manipulation, scientists have been able to insert the gene coding for this biological pesticide into plants such as corn and potatoes. These transformed plants better resist pests, which reduces the need for pesticides.


© Armand-Frappier Museum, 2008. All rights reserved.

Learning Objectives

The learner will:
  • familiarize himself with the vocabulary used in microbiology;
  • explain the relationship between developments in imaging technology and the current understanding of the cell;
  • identify which microorganisms are infectious, how the immune system fights against them, and the reinforcements of modern medicine;
  • describe the benefits of microorganisms .

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