Genetics and molecular biology

• DNA forms the genetic material of living organisms
• Understanding the human genome remains a complex challenge despite advancements
• DNA consists of a sugar-phosphate backbone with four nitrogen-containing bases: Adenine (A), Thymine (T), Guanine (G), and Cytosine (C)
• Adenine pairs with Thymine, and Guanine pairs with Cytosine, forming a double helix structure
• Chromosomes in the nucleus contain DNA and histone proteins, organizing genetic material
• The human genome comprises approximately 3 billion base pairs divided into 46 chromosomes
• Somatic cells have pairs of chromosomes (diploid), while gametes are haploid, containing a single set of chromosomes
• There are 22 pairs of autosomal chromosomes and one pair of sex chromosomes (XX for females, XY for males)
• Chromosomes are homologous, containing similar genetic information
• Chromosomes are visualized through a karyotype, showcasing their structure and organization
• Heterochromatin is condensed chromatin, transcriptionally inactive, and contains large numbers of tandem repeats
• Genes are coding regions of DNA responsible for producing proteins
• Genes consist of exons (protein-coding) and introns (non-protein coding)
• Pseudogenes are non-functional genes
• The Central Dogma describes the flow of genetic information from DNA to RNA to proteins
• DNA consists of deoxyribonucleotide units linked by phosphate groups
• Four nitrogenous bases (Adenine, Guanine, Thymine, Cytosine) are bonded to the sugar-phosphate backbone
• Adenine and Guanine are purines, while Thymine and Cytosine are pyrimidines
• Nucleoside: Base bonded to a sugar (Deoxyadenosine, Deoxyguanosine, Deoxythymidine, Deoxycytidine)
• Nucleotide: Nucleoside + Phosphate group
• DNA is double-stranded, with two antiparallel polynucleotide chains twisted into a helical structure
• Adenine pairs with Thymine (2 H bonds), and Guanine pairs with Cytosine (3 H bonds)
• Chargaff’s Rule states that the amount of A = T and C = G in DNA samples
• RNA contains Ribose sugar, is single-stranded, and uses Uracil instead of Thymine
• DNA profiling relies on variations in repeated sequences called 'core sequences' or 'alleles'
• DNA contains Deoxyribose sugar, is double-stranded, and uses Thymine
• Individuals inherit two alleles, one from each parent, at each locus (specific position on a chromosome)
• Techniques involve separating and typing repeat units, forming the basis of DNA profiling
• The first legal case involving DNA profiling linked the same individual to two crimes in Leicestershire
• Colin Pitchfork became the first individual convicted with the help of DNA profiling
• Sir Alec Jeffreys discovered repeat sequences in the myoglobin gene, laying the foundation for DNA profiling
• DNA profiling techniques have evolved from Multi Locus Probes to Short Tandem Repeat (STR) technology
• Restriction Fragment Length Polymorphisms (RFLPs) detected variations in DNA sequences through gel electrophoresis
• Recombinant DNA technology enabled the production of therapeutic products like insulin and human growth hormone
• DNA must be separated from other cellular components and non-biological material for accuracy in downstream procedures
• Factors affecting DNA extraction include the source of DNA, sample amount, cell types present, and quality needed for downstream applications
• Ideal forensic DNA extraction methods yield high DNA concentration, remove substances interfering with PCR, and maintain sample integrity
• Examples of biological materials for DNA extraction include blood, food samples, bacteria, semen, bones, teeth, hair, saliva, urine, and more
• Temperature, humidity, light, exposure to chemicals, and time can degrade DNA
• DNA extraction methodologies include Phenol/chloroform, Chelex, silica-based commercial kits, and differential extraction