8.1

What is biotehcnology?

The use of biological processes to produce useful products

What is DNA?

Deoxyribonucleic acid

Where is DNA found?

Cells of all organisms, usually the nuclues

some in the mitochondria

some in cytosol

Stucture of DNA

Conssits of two strands of nucleotides

Each nucleotide is made up of deoxyribose sugar molecule, phosphate group and nitrogenous base

When these nucleotides join together, it makes the backbone of an alternating deoxyribose sugar and phosphate with nitrogen bases branching at each sugar molecule

bases from two strands are attached to one another by hydrogen bonds and this forms cross links between the two strands

DNA molecule twisted into spiral called a double helix

What are the 4 nitrogenous bases in a DNA molecule?

Adenine

Thymine

Cytosiine

Guanine

What does the order in which nitrogenous bases occur in the DNA molecule determine?

The genetic information that determoines the structure and function of the cells

What is artificial selection/selective breeding

An ancient form of genetic engineering where humans select desired traits and choose parents based on these traits

How does artificial selection work>

• Select which male and female organisms are crossed to produce offspring

• increases chance of certain genes being present in the DNA of the next gen

• if parents with desired traits are chosen, we can increase the chance of the gene fro those phenotypes being passed on

• when parents without desirable traits are chosen, there is a decreased chance of the genes for that phenotype occuring in the next generation

• In this manner, we can increase or decrease the incidence of certain genes

Limitations of artificial selection?

Quite slow and inefficient

genes are passed on by chance and it is necessary to wait for thenext gen to mature before knowing the outcome

What is an alternative to artificial selection?

Genetic engineering

What is genetic engineering?

The procedures used to produce recombinant DNA; involve introducing DNA into a cell from a different type of organism or DNA that has been modified in some way

Process of genetic engineering?

DNA is either added or removed from a cell

DNA produced is recombinant DNA and the organism is a genetically modified organism

What is recombinant DNA

Synthetic DNA; made by inserting genes from one source into a DNA molecule from a different source

What can genetic engineering be used for?

Introducing genes for desired traits into organisms, using harmless bacteira to produce proteins, and replacing faulty genes

What are the applications of genetic engineering?

DNA from one species being introduced into a different species

the organism produce is a transgenic organism

What is the aim of transgenic organisms?

Introdcue a trait that is not normally present

What is a transgenic organisms

An organism that has had DNA from another species introduced into it artificially

All transgenic organisms are GMO’s, but not all GMO’s are transgenic

An example of a transgenic organism?

Golden rice, which was developed to address vitamin A deficiency in developing countries

deficiency kills 670,000 children under the age of five every year

Golden rice produced by introducing a gene from maize and a bacterium found in soil into rice

allows the rice to produce beta carotene, which the human body can use to synthesise vitamin A.

Who invented recombinant DNA technology

Stanely Norman Cohen and Herbert Boyer

Technique was to isolate and amplify genes or DNA segments and insert them into a bacterial cell, creating a transgenic bacterium

Introduced genes become part of the transgenic organisms DNA and can be passed on from one generation to the next

What must happne for genetic engineering to be possible?

Gene for desired trait must be identified and isolated

DNA recieving the gene must be opened

gene is then added to the recipient and joins its DNA

What are bacteriophages

Viruses that infect bacterial cells

What was discovered about bacteriophages?

Certain enzymes in bacteria can restrict duplication of bacteriophages by cutting up the viral DNA

Scientists found that these enzymes always cut the DNA at a point where there is a certain sequence of bases

What is a recognition site?

A specific sequence of nucleotides at which an enzyme cuts a strand of DNA

Four to eight base pairs in length

Palindromic (same sequence when read both forwards and backwards)

this + complementary nature of bases means that same sequence occurs on both strands within recognition site

Both strands will be cut, resulting in the DNA molecule forming two segments

Each restriction enzyme will recognise certain base sequence and cut at a certain point

What is a restriction enzyme?

An enzyme that cuts strands of DNA at a specific sequence of nucleotides

Some restriction enzymes produce straight cut at the sequence, while others produce a staggered cut

Why are they called restirction enzymes?

Restricts the duplication of DNA

What are endonucleases?

An enzyme that breaks a nucleic acid within the strand by separating two nucleotides

What is a straight cut?

When the restriction enzyme makes a clean break across the two strands of DNA to produce a blunt end

Blunt end is where both strands terminate at a base pair

What is a staggered cut?

A cut produced when a restriction enzyme creates fragments of DNA with unpaired nucleotides that overhang at the break in the strands; called sticky ends

Why are they called stick ends?

Because of their ability to combine with sections of DNA that have a complementary ending

Useful in recombinant DNA tech as they allow single stranded overhang from one DNA fragment to be paired with any other piece of DNA that has a corresponding sequence

How are restriction enzymes named?

First letter of name → genus of the bacteirum from which it was isolated

Second two letters → come from the specieis

Next letter → strain of bacterium

roman numerals → when the enzym ewas isoalted, where I is the first enzyme isolated, II

What is DNA ligase?

An enzyme capable of combining two small components of single-strand DNA into one single structure

What is ligation?

How does DNA ligase work?

By joining the phosphate group at the end of one strand to the sugar molecule at the end of another strand

For this to be possible, complementary bases must first join by forming hydrogen bonds. Then the DNA ligase can join the backbone of each strand

What is a vector?

A DNA molecule used to carry DNA into a cell

What is the process of producing an organisms with recombinant DNA?

1) Identifying the desired gene

2) Using a restriction enzyme to cut the DNA on either side of the gene

3) Using the same restriction enzyme to cut the DNA of the vector

4) Adding the desired gene to the vector

5) Using DNA ligase to join the two sections of DNA

6) Cloning of vector then occurs so that numerous copies of DNA are available to insert into the host cells.

7) Large quantity of vector produced, they can be introduced into the selected host cells such as special bacterial, yeast or mammalian cells

8) Host cells will produce foreign protein using instructions in the gene int he recombinant DNA

Simplified Diagrammatic representation of RDT

What are the most common used vectors?

Bacterial plasmids and bacteriophage viruses

What are plasmids?

Circular, double stranded units of cytoplasmic DNA, frequently found in bacteria that are capable of replicating within a cell independently of the chromosomal DNA.

Gene of interest is integrated into the plasmid or phage, and is reffered to as recombinant DNA.

What is the impact that recombinant DNA tech has had?

• Improved diagnosis and treatment of diseases and genetic disoredrs

• Enabled the manufacture of large quantities of pure protein for many meidcal products such as insulin, growth hormone, follicule stimulating hormone (in the past, these substances had to be extracted from people or animals, and were often impure and of variable strength)

What are recombinant vaccines?

Vaccines produced using recombinant DNA

Most vaccines being investigated are focused on using recombinant bacterium E coli or cells from mammals, insects or yeast to produce protein antigens. These can be introduced to the body, where they will elicit an immune response

Antigen is produced → introduced in the vaccine

First vaccine that used RDT was hepatitis B vaccine.

Produced by inserting a gene from the hepatitis B virus into the cowpox virus

How does the Hepatitis B vaccines work?

gene for a surface antigen on the virus is isolated and added to a plasmid

plasmid is introduced into a yeast cell

when yeast cell divides, new cells also contain plasmid with gene for antigen

gene allows yeast cell to produce the antigen protein, which can be collected and purified

How does the HPV vaccine ork?

Produced in very similar process, using recombinant. yeast or insect cells

cells produce proteins that are found on the coat of the virus and are collected to be used in the vaccine

What are DNA vaccines?

Difference between recombinant vaccines and DNA vaccines

RV → antigen is produced and then introduced in the vaccine

DNAV → DNA for the antigen is introduced in the vaccine instead of the antigen itself. DNA is incorportaed into the hsot cells, which will produced the antigen. Thought is that antigen will then be expressed by the host cells, in a similar way to what happens during a viral infection

Disadvantages of developing recombinant DNA vaccines?

• Expensive as genes for desired antigens must be located, cloned and expressed efficiently in a new vector

• Those involved in vaccine research must also be conservative (because vaccines are used on a large number of healthy people, many of whom are children, safety must be paramount. therefore if a conventional vaccine is known to be safe, there is little incentive to develop new one using genetic engineering