The Gene Revolution: Exploring the World of Biotechnology
The Gene Revolution: Biotechnology
Historical Introduction
Friedrich Miescher (1871)
Swiss biologist Friedrich Miescher, while working with white blood cell nuclei, discovered a substance he called “nuclein,” later known as deoxyribonucleic acid (DNA).
Frederick Griffith (1879-1941)
British geneticist Frederick Griffith discovered the “transforming principle” (DNA) through experiments demonstrating bacteria’s ability to transfer genetic information via transformation.
Griffith’s Experiment
Oswald Avery, McLeod, and McCarty (1944)
This team purified the “transforming principle,” confirming DNA as the molecule responsible for bacterial transformation.
Alfred Hershey and Martha Chase (1952)
Confirmed that DNA, not protein, carries genetic instructions in cells.
Rosalind Franklin (1952)
English biophysicist Rosalind Franklin’s X-ray diffraction image (Photo 51) suggested DNA’s double helix structure, crucial for confirming the molecule’s structure.
DNA: The Secret of Life
Deoxyribonucleic acid (DNA) transmits genetic information for all living organisms. This large molecule comprises nucleotides, each consisting of phosphoric acid (phosphate), a pentose sugar, and a nitrogenous base.
Nucleotides
Nucleotides join in unbranched chains. Their sequence determines protein synthesis, essential for life.
Nucleotide Sequence
DNA: A Double Helix
DNA consists of two nucleotide chains twisted into a double helix. The chains are chemically complementary, with nitrogenous bases binding on the inner face.
Viral DNA can be linear or circular, enclosed in a protein coat (capsid).
Prokaryotic, mitochondrial, and chloroplast DNA is typically circular.
Eukaryotic DNA combines with histones to form chromatin, condensing into chromosomes during cell division.
Each chromosome segment (gene) instructs protein synthesis.
DNA Replication and Information Transfer
DNA replicates by opening like a zipper, each strand serving as a template. DNA polymerase adds nucleotides (A=T, C=G). Two identical DNA molecules result, each with an original and a new strand. Errors during replication can cause mutations, some leading to diseases or contributing to evolution.
Genes and Proteins
Genes contain information for protein synthesis. Proteins, formed from amino acids, have diverse functions, giving each individual and species its specificity.
Translation (Protein Synthesis)
mRNA joins a ribosome, which reads and translates the genetic code to synthesize proteins. Each mRNA triplet (codon) corresponds to an amino acid, transported by tRNA.
Biotechnology: A Set of Technologies
Biotechnology has long been used, from fermentation to microorganism use in agriculture. Modern biotechnology involves manipulating DNA to modify products, improve organisms, or develop microorganisms for specific uses.
Techniques include cutting, isolating, pasting, reproducing, and sequencing DNA fragments. Recombinant DNA combines DNA segments from different sources.
Recombinant DNA Technology
Cellular Enzymes
Restriction enzymes cut DNA.
Ligases join DNA fragments.
DNA Fragment Analysis (Agarose Gel Electrophoresis)
Separates DNA fragments by size and charge, creating a characteristic banding pattern.
DNA Probe Hybridization
Uses labeled DNA probes to detect specific genes.
DNA Microarrays (Biochips)
Analyze thousands of genes simultaneously.
DNA Cloning
Creates billions of identical DNA fragment copies using vectors like bacterial plasmids.
DNA Amplification (PCR)
Copies specific DNA segments in vitro.
DNA Sequencing
Determines the nucleotide sequence of a DNA fragment.
Genetic Engineering
Manipulates DNA to create new life forms with unique gene combinations. Applications include genetically modified organisms (GMOs) and gene therapy.
Genetically Modified Organisms (GMOs)
Organisms containing a transgene from another organism. Used for bioremediation, industrial applications, pharmaceuticals, and agriculture.
Gene Therapy
Treats diseases by introducing a functional gene. Can be somatic (targeting specific cells) or germline (modifying the entire genetic code).
Cloning
Creates genetically identical organisms. Reproductive cloning involves nuclear transplantation.
Stem Cells
Undifferentiated cells that can differentiate into specialized cell types. Can be totipotent, pluripotent, or multipotent.