DNA technologies

The structure of DNA revealed by Watson and Crick allowed scientists to further understand how DNA influences the functioning of living organisms.
Techniques such as DNA sequencing and DNA profiling were developed to explore the sequence of genes along DNA.
- DNA Sequencing: The precise order of nucleotides in a DNA sample is determined.
- DNA Profiling: An organism's unique DNA profile is characterized as a distinct series of bands.

Definition: Determining the exact nucleotide sequence of a chromosome, revealing the order of bases A, T, G, and C.
Various methods of sequencing DNA:
- Manual methods: Sanger chain termination method, Maxam-Gilbert method.
- Automated methods: Using DNA sequencers that can process DNA rapidly.
Sanger Method:
- Developed by British biochemist Fred Sanger; also referred to as dideoxy DNA (ddDNA) sequencing.
- Automation allows for sequencing approximately 1000 bases per second.
- Steps:
  1. Isolate DNA from the organism's cells.
  2. Conduct sequencing reactions involving a reaction mixture: primer, DNA template, DNA polymerase, ddNTPs (dideoxynucleotide triphosphates), and dNTPs.
  3. Use capillary electrophoresis to separate DNA fragments by length.
  4. Analyze results via computer.
Sequencing Reaction Steps:
1. Heat the double-stranded DNA to separate it into single strands.
2. A primer binds to the single strand's start.
3. DNA polymerase builds the complementary DNA strand using free nucleotides.
4. Dideoxy nucleotides terminate the chain when incorporated, preventing additional nucleotides from attaching.
Fluorescent Labeling: Each type of dideoxy nucleotide is labeled with a different fluorescent dye, leading to chains of varied lengths identifiable by color during analysis.

Involves chemical sequencing of the DNA strand, utilizing hazardous chemicals, which limits its usage.
Based on nucleotides that are specific to pyrimidines (C and T) and purines (A and G).
Process:
1. One end of the DNA strand is radioactively labeled.
2. Conditions are modified to cleave the strand at specific bases.
3. Fragments undergo gel electrophoresis to determine sequence.

New techniques are faster, cheaper, and capable of sequencing multiple fragments simultaneously.
Example - Nanopore Sequencing:
- DNA molecules pass through a protein nanopore, generating a change in current, indicating base identity.
- Capable of processing 450 base pairs per second across multiple nanopores.

Also known as DNA fingerprinting; a method to identify and compare individuals based on DNA characteristics.
Developed by Sir Alec Jeffreys, useful in forensics, paternity testing, and biological studies.
STRs (short tandem repeats): Unique sections of non-coding DNA with variable repeats among individuals contribute to distinct DNA profiles.
Process:
1. Isolate DNA from somatic cells (e.g., saliva, blood).
2. Amplify using PCR to amplify the region of interest.
3. Use gel electrophoresis to separate fragments by length, showing unique banding patterns.

Issues of DNA ownership and access arise after analysis.
Concerns over genetic testing implications for insurance companies and potential discrimination against applicants.
The debate over patenting genetic mutations and restrictions in various countries against genetic testing for insurance purposes.
2013 US court ruling: genes cannot be patented, impacting thousands of patents.