What is DNA?

• DNA is considered the genetic material
• Professor Wayne McLaughlin presented the information

DNA Basics

• DNA is the "Molecule of Life"
• All animals, plants, bacteria, and some viruses have DNA
• DNA makes up our genes
• Within the human body contain 75 Trillion Cells
• If stretched out, the DNA from each are 2 metres long

Exploring DNA

• Exploring the history behind the discovery of DNA through classical experiments
• DNA applications include: Medicine, Science, Ancestry, Forensic Science, and Agriculture

Early Understanding

• Genes are located on chromosomes, which was discovered in 1866
• Chromosomes contains both DNA and proteins
• There was no evidence at this time that DNA carried genetic material

DNA Discovery

• In 1869 Friedrich Miescher, while studying pus in bandages from the Crimean War, discovered a large molecule in the nucleus of cells
• Miescher called the molecule ‘nuclein’
• Miescher had discovered deoxyribose nucleic acid - DNA

Establishment of DNA as Genetic Material

• Through a series of experiments using bacteria and viruses, proving that DNA is the genetic material

Genetic Transformation

• Frederick Griffith first suggested that bacteria can transfer genetic information through transformation

Transformation Experiments

• Fred Griffiths (1928) experimented with Streptococcus pneumoniae
• The pneumonia-causing strain was surrounded by a capsule/polysaccharide giving the organism a smooth-edged colony on an agar plate
• This is also know as the type III "S" strain
• A different strain did not have a capsule and produced a rough-edged colony on an agar plate
• This is also known as the type II "R" strain and was considered non-virulent in mice
• In an experiment Material in dead bacterial cells can genetically transform living bacterial cells
• Dead S strain cells mixed with living, nonvirulent R strain bacteria result in mouse death
• The dead S strain was re-animated/resurrected.
• The live R had become "transforming factor" and transformed into Live- S

Griffith's Hypothesis

• A chemical component from the virulent S cells had somehow transformed the R cells into the more virulent S form

Further Research

• Pathogenicity is caused by the capsule gene – S allele
• The capsule allows the bacteria to survive in a vertebrate host
• If the R-allele of the gene is present, no capsule is formed

Heat-Killed Cells

• Genetic components remain undamaged in heat-killed cells
• Components of heat-killed cells can bring about genetic changes in the recipient cell

DNA transformation

• DNA molecules can re nature after heat treatment
• Bacteria can take up foreign DNA from the environment through transformation

Competence

• Some bacteria can enter and take up naked DNA from the environment
• Bacillus subtilis is not a human pathogen
• S. pneumoniae can cause pneumonia and conjunctivitis
• Helicobacter pylori can cause stomach ulcers
• Neisseria spp can cause gonorrhea
• Haemophilus spp. can cause influenza and conjunctivitis

1944

• Studies confirm the chemical nature of the substance inducing transformation of Pneumococcal types
• O.T. Avery, C.M. MacLeod, and M. McCarty published their findings in J. Exp. Med. 79, 137-159 (1944)
• McCarty's team showed on February 1, 1944, that DNA is the material of inheritance
• Until this point biologists originally thought genes (the units of inheritance) consisted of protein

Pure DNA

• DNA was isolated by McCarty's team in 1944 and used to conduct experiments
• Results suggested that DNA was the molecule responsible for transformation

Evidence for Transformation

• Transformation was caused by DNA, proven through chemical analysis, physical properties, protein hydrolyzing enzymes and nucleic acid hydrolyzing enzymes
• People were were reluctant and not convinced DNA as considered the genetic material DNA as a structural component of chromosomes while genes are likely a component of proteins

Blender Experiment (Alfred Hershey - 1952)

• The experiment confirmed the DNA itself (not the protein) caused the transmission of genetic information
• Genes are made of the nucleic acid DNA
• Viruses and Bacteria can be used as models to study universal principles of genetics

Bacteriophage T2

• Bacteriophage T2 consists of a head, neck, collar, sheath, tail fiber and base plate
• Also includes DNA

Viruses and Cells

• Bacteriophage attaches to E. coli and injects its chromosome
• Bacterial chromosome breaks down and the phage chromosome is replicated
• Expression of phage genes produces phage structural components
• Progeny phage particles assemble
• Bacterial wall lyses, releasing progeny phages.

Labeling of Phage

• DNA was labelled with 32P
• Protein capsule was labelled with 35S

Hershey & Chase Conclusions

• Phage DNA was essential for producing offspring/progeny
• Protein formed a protective coat around the bacteriophage

Historical Discovery of Structural DNA

• On April 25, 1953, James Watson and Francis Crick first described the double helical structure of DNA
• They also noted that this structure suggests a mechanism for copying genetic material
• Wilkins, Stokes and Wilson analyzed the X-Ray crystallography evidence and suggesting the structure occurs in biological systems (same day)
• On May 30, 1953, Watson and Crick followed up with speculation on how base pairings occur at the double helix, enabling DNA replication

The Genetic Revolution

• Determining the structure of DNA established in the 1960s allowed that three-letter DNA 'codons' and the foundation for instructions of building proteins
• This was the dawn of New era of Molecular Biology

DNA and Technology

• Molecular Medicine, Molecular Genetic Diagnostics, Pharmacogenomics, and Personalized Medicine are all areas of exploration

Molecular Medicine - 2020 Expectations

• More effective pharmaceutical made by recombinant DNA technology
• Full/complete genome as well as a catalog of single base-pair variations that can accurately predict responses to certain drugs and environmental substances
• Predicitng susceptibility to specific diseases to allow for modifications to lifestyles, such as altering reduce the likelihood or preventive treatments

Personalized Medicine

• Rapidly advancing field of healthcare informed by each person's clinical, genetic, and environmental information

DNA Uses

• DNA analysis is useful in Criminal investigations, Parentage testing and Ancestry testing
• It aids in sexual assault, homicide and minor crimes. In cases of property crime. DNA helps exonerate the innocent and identifies the remains and victims of missing persons

Biotechnology benefits

• Biotechnology benefits agriculture
• GM Papayas can have delayed fruit ripening and virus resistance