8.1 Recombinant DNA

Applications of biotechnology

DNA

deoxyribonucleic acid, is found in cells of all organisms, usually in the nucleus, but can also be found in the mitochondria and in some organisms the cytosol.

All DNA molecules …

Consist of two strands of nucleotides. Each nucleotide is made up of deoxy ribose sugar molecule, a phosphate group and a nitrogenous base.

Shape of DNA molecule

Double Helix

A

Adenine

T

Thymine

C

Cytosine

G

Guanine

Order of nitrogenous bases

The order in which the nitrogenous bases occur in the DNA molecule is the genetic information that determines the structure of the cell and the way it functions.

Artificial Selection/Selective Breeding

Increasing or decreasing the incidence of certain genes, by selectively choosing the parents of an organism.

Genetic Engineering/ Recombinant DNA technology

The artificial modification of DNA, where DNA is either added or removed from a cell.

DNA produced from genetic engineering

recombinant DNA

Organism produced from recombinant DNA technology

genetically modified organism

Transgenic Organism

The organism produces when DNA from one species is introduced to another species.

Aim of Transgenic organisms

Introduce a trait that is not normally present in a species.

Relationship between transgenic organisms and GMO’s

All transgenic organisms are GMO’s not all GMO’s are transgenic.

Transgenic organism EXAMPLE

Golden Rice, developed to address vitamin A deficiency in developing countries. This deficiency kills 670 000 children under the age of 5 every year. Golden rice was produced by introducing a gene from maize and bacterium found in soil into rice. This allows the rice to produce beta-carotene, which human body can use to synthesize vitamin A.

Development of recombinant DNA technology

Stanley Norman Cohen and Herbert Boyer invented the recombinant DNA technique in 1973.

Restriction Enzymes

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

Recognition Sites

A specific sequence of nucleotides at which an enzyme cuts a strand of DNA. The complementary nature of the bases means that the same sequence occurs on both strands within the recognition site.

Endonucleases

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

Straight Cut

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

Blunt End

Is when both strands terminate in a base pair.

Staggered Cut

results in fragments with sticky ends

Sticky ends

is a stretch of unpaired nucleotides in the DNA molecule that overhang at the break in the strands.

palindromic

meaning they have the same sequence when read both backwards and forwards.

Factors that contribute to the type of cut

Restriction enzyme will:

• Recognise a certain base sequence

• cut at a certain point.

Sticky ends are so named because…

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

Naming Rules for restriction enzymes

• the first letter of the name comes from the genus of the bacterium from which it was isolated.

• the second two letters come from the species

• The next letter refers to the strain of the bacterium

• The roman numerals represent when the enzyme was isolated, where I is the first enzyme isolated and II is the second enzyme isolated etc.

DNA ligase

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

Ligation

The process of joining short strands of DNA during replication.

Vector

A bacterial plasmid, viral phage or other such agent used to transfer genetic material from one cell to another.

Plasmids

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