Chapter 1: Approaches to Studying Biology at the Molecular Level

Approaches to Addressing Biological Questions at the Molecular Level

Genetic Approach

Studying/Altering genes to learn about function of gene products in vivo

  • Forward Genetics: Find mutant and identify what causes phenotype
  • Reverse Genetics: Find gene of interest and create mutant (using introduction of additional sequences: transgenes) and observe phenotype
  • Transgenes: Genetic material transferred to an organism which may alter phenotype
  • Silence Genes: miRNA and siRNA complementary to target mRNA and 2 products will anneal and produce ds RNA which is degraded by RNase because it looks like viral RNA reduce expression of target genes to see impact

Mutants

  • Mutagenize using mutagens such as chemicals, radiation or genetic element (CRISPR, transposon)
  • Substitution – Single Nucleotide Polymorphism SNP
  • Small Insertion or Deletion – called indels, can result in frameshift mutations
  • Larger Insertions of Deletions or Inversions
  • Screen (look at each individual and identify altered) or Select (mutant has growth advantage)


Biochemical Approach

Studying proteins or metabolites in vitro

  • Prepare an assay mix with enzyme/protein in active state, can learn optimal temp/pH, rxn rate, pI, structure
  • Extract: Homogenized tissue via sonicator/blender/mortar pestle/ bead breaker (yeast)
  • Assay: Quantitative measure of protein/enzyme activity or developmental trait

Bioinformatic Approach

creation of databases of large data and mining data to make predictions/models in silico

  • Before other approaches, the combination of biology and computer science involving collection of protein and nucleic acid into searchable databases for comparative analysis
  • Gene Sequencing of mutant may reveal other family members, similar genes, sites of mutation
  • Scan complete genome sequence for genes encoding related enzymes, number of copies of enzyme gene, amino acid structure

Model Organisms

Organisms used to represent a population, these are much simpler than the ones they represent and less complex

  • Sequence complexity: one copy of each repeat sequence + length of unique sequence not same as length

Common traits for model organisms (E. Coli, Saccharomyces cerevisiae, Drosophila melanogaster, Xenopus laevis)

  • Smaller genome size: fewer genes to search through, map, sequence
  • Low amount of repetitive DNA: Repetition in DNA complicates hybridization experiments & sequencing
  • Diploid (not all): hard to pinpoint and mutate genes (too many copies of gene)
  • Short life cycle: helps high generation #, see how the gene is regulated and its impact on next generation
  • Small, cheap: can house many in small space and perform higher # of samples
  • Transformable: allows for gene manipulation

Pros

  • Share data, cost effective
  • Validate results
  • Share techniques/research moves faster
  • Aid large scale experiments & benefit whole community

Cons

  • Too competitive
  • Model organisms may not have specific trait
  • All organisms raised in artificial environments

Species can't accurately represent whole population

Note Created by
Is this note helpful?
Give kudos to your peers!
20
Wanna make this note your own?
Fork this Note
41 Views