Applications of reproduction and genetics

• DNA sequencing


  1. Mapping

  2. Fragmentation with restriction enzymes

  3. Insertion into bacterial artificial chromosomes

  4. Formation of genomic DNA library

  5. Fragmentation and sequencing with chain-termination method
• Chain-termination sequencing method


  • Based on selective incorporation of chain terminating nucleotides into a growing chain by DNA polymerase during replication
• Chain-termination sequencing


  1. DNA sample divided into 4 reactions with standard nucleotides, DNA polymerase, primers and fluorescently labelled modified nucleotides

  2. Modified nucleotides terminate replication

  3. DNA fragments of different lengths formed

  4. Fragments separated by size using high resolution electrophoresis

  5. Fragments visualised under UV light to read base sequence

  
• Rapid advancement of sequencing techniques increased speed and allowed whole genome sequencing
• Genome-wide comparisons


  Comparing genomes between individuals and between species
• Significance of genome comparisons

  • Allows determination of evolutionary relationships between species
  • Beneficial for medical research
• Personalised medicine


  Development of treatments tailored to a particular genome
• Gene sequencing allows prediction of amino acid sequences in polypeptides and development of synthetic biology
• Human Genome Project


  International scientific project that determined the sequence of bases in a human genome
• Potential applications of the Human Genome Project include screening for mutated sequences, carriers, pre-implantation screening, and screening for disorders like Huntington's disease
• There are many ethical concerns regarding the Human Genome Project, such as discrimination and misuse/ownership of genetic information
• DNA profiling


  Forensic technique used to identify individuals by characteristics of their DNA and determine genetic relationships
• Polymerase chain reaction (PCR)

  1. Reaction mixture set up with DNA sample, primers, nucleotides and DNA polymerase

  2. Mixture heated to 95°C to separate strands

  3. Cooled to 50-65°C for primers to bind

  4. Temperature increased to 70°C for DNA polymerase to create copies

  5. Cycle repeated 30 times to amplify DNA

  
• Gel electrophoresis


  Process used to separate DNA fragments and proteins by size using an electric current

  
• Genetic engineering - inserting DNA fragments into plasmids

  1. Plasmid and gene cut with same restriction enzyme to create complementary ends

  2. Fragments incubated with plasmids, base pairing and DNA ligase forms recombinant DNA
• Transgenic microorganisms


  Electroporation used to increase permeability of bacterial membranes and facilitate uptake of plasmids
• Bacteria with successful plasmid uptake can be selected using marker genes like antibiotic resistance
• Other vector types include bacteriophages, liposomes and yeast artificial chromosomes
• Cystic fibrosis


  Genetic disorder caused by mutation in gene coding for CFTR protein, which transports chloride ions and affects mucus, leading to problems in respiratory, reproductive and digestive systems
• Gene therapy


  Insertion of normal allele into target cells to replace faulty allele
• Somatic gene therapy


  Allele introduced to target cells only, short-term solution
• Germ line gene therapy


  Allele introduced to embryonic cells, permanent solution passed to offspring
• There are ethical considerations regarding genetic engineering, including potential environmental impacts and accessibility for poorer farmers
• Bioinformatics


  Science of collecting and analysing biological data using computer software
• Bioinformatics can be used to build databases of gene sequences and genomes, identify human gene counterparts in other organisms, and study parasite genomes to develop new control methods
• Genetic screening


  Screening for genetic conditions like breast cancer, used for preimplantation genetic diagnosis and prenatal testing
• Preimplantation genetic diagnosis


  Embryos created through IVF tested for genetic disorders before implantation
• Chorionic villus sampling


  Embryonic tissue sample taken from placenta at 8-12 weeks for DNA analysis
• Amniocentesis


  Amniotic fluid sample obtained at 14-16 weeks, fetal cells grown in culture for DNA analysis
• There are social and ethical issues surrounding genetic testing, including risks, outcomes, and emotional/financial impacts
• Genetically modified crops


  Crops modified for herbicide or insect resistance to increase yield, but risk of transferring genes to wild relatives
• Examples of GM crops include herbicide-resistant soybeans and insect-resistant Bt maize
• Genetically modified crops like golden rice can help address nutritional deficiencies, but are expensive and not accessible to all farmers
• Stem cells


  Undifferentiated cells that can divide to give rise to other cell types, including pluripotent and totipotent cells
• Stem cells can be sourced from embryos, adults, and fused cells, and used to treat diseases and replace damaged tissues
• There are ethical issues regarding stem cell use, including embryo destruction, infection risks, and potential for cancerous growth