Answer: Phylogenetic trees visualize the evolutionary relationships among organisms or genes, helping researchers understand how diseases spread and evolve. By examining genetic similarities and divergences, phylogenetics can identify how closely related different strains are and track the transmission pathways of pathogens, including between species and populations.
Answer: The criteria include measuring the construct of interest (e.g., detecting the pathogen), ensuring sufficient discrimination between strains, reliability and reproducibility of results, handling requirements (e.g., specimen collection, storage), and cost-effectiveness for large-scale or prolonged studies.
Answer: PFGE is time-consuming, taking 3-5 days for results, which delays outbreak investigations. Additionally, the genome is not always cuttable by restriction enzymes, and identical band patterns do not always mean identical genomes, leading to potential misidentification of strains.
Answer: PCR is fast and effective for detecting the presence of a pathogen, but it does not provide information about genetic variation within a species. Full genome sequencing, while more detailed and informative for understanding strain differences and transmission, is more expensive and time-consuming.
Answer: Molecular epidemiology helps trace the source and transmission pathways of diseases quickly, allowing for targeted interventions and prevention measures. For example, in the 2016 E. coli outbreak, PFGE and other molecular tools identified a goat farm as the source, leading to specific public health actions that prevented further spread.
DNA methylation adds a methyl group to CpG islands, suppressing gene expression, while histone modifications (like acetylation) can either relax or condense chromatin to allow or block access to transcription machinery.
The Agouti mouse model shows that maternal diet, rich in genistein, can increase DNA methylation, leading to fewer offspring with the "yellow" obese phenotype, demonstrating that nutrition can directly modify gene expression through epigenetic changes.
miRNAs bind to mRNA transcripts, either degrading them or preventing translation. In dairy cows, miRNA-152 affects lactation by regulating the expression of genes involved in milk production through its impact on DNA methyltransferases.
Female mammals have two X chromosomes, one of which is randomly inactivated in each cell. In calico cats, this results in mosaic expression of coat color genes, which are located on the X chromosome.
Cancer can result from both hypermethylation of tumor suppressor genes, leading to their silencing, and hypomethylation of proto-oncogenes, causing overexpression and uncontrolled cell division.
Creating recombinant DNA in E. coli involves identifying the gene of interest, inserting it into a vector, transforming the vector into E. coli, and selecting/confirming rDNA clones. For mammalian cells, transformation/transfection into host cells is followed by confirmation of protein expression and purification.
E. coli is beneficial for high yields and low costs, but it lacks post-translational modifications. Mammalian cells offer more accurate protein folding and modifications, suitable for therapeutic use but are costlier and slower.
Engineered insulins like Lispro and Glargine offer modified pharmacokinetics. Lispro is designed to act quickly by inhibiting dimerization, whereas Glargine provides a prolonged effect due to pH-based solubility changes.
Monoclonal antibodies are generated by hybridoma cells from B-cells fused with myeloma cells. Caninized antibodies reduce immune reactions by replacing murine sections with canine sequences, increasing treatment efficacy in dogs.
Restriction enzymes cut DNA at specific sequences, facilitating insertion into vectors. DNA ligase joins DNA fragments, enabling the creation of stable recombinant molecules.
Ethical implications include concerns about animal rights and potential negative effects on natural ecosystems. Practical challenges include high costs, low success rates, and health issues in cloned animals, especially related to genetic and epigenetic reprogramming errors.
Embryo twinning mimics natural twin formation and is simpler but limited in clone numbers. SCNT is more flexible and allows cloning from somatic cells, producing a broader range of clones, though it's technically demanding and less efficient.
Genome editing improves welfare by reducing procedures like dehorning through genetic modifications, as seen in hornless cows, and improving disease resistance, as in PRRSV-resistant pigs.
Zinc Finger Nucleases and TALENs use protein-DNA recognition, which requires complex engineering, whereas CRISPR/Cas9 relies on RNA-DNA targeting, making it more flexible and accessible.
Off-target effects pose risks by potentially causing unintended mutations, impacting genomic stability, and leading to unwanted phenotypes. They raise concerns for clinical use due to possible unintended health impacts.
Pluripotency: The ability to form all cell types derived from the three germ layers. It is tested via in vitro differentiation, teratoma assays, and chimeric assays.
Pluripotent cells can form all cell types in the body (e.g., embryonic stem cells), while multipotent cells are limited to specific lineages (e.g., hematopoietic stem cells forming blood cells).
iPSC Creation: Somatic cells are reprogrammed using factors like Oct4 and Sox2. This avoids ethical issues of embryonic stem cells and enables autologous therapies.
Regenerative Medicine: iPSCs replace damaged retinal cells in macular degeneration, showcasing the potential of autologous therapies.
Ethical Concerns: Embryonic stem cell research involves the destruction of embryos, raising questions about the moral status of early human life.