Skills: Using Databases (DP IB Biology: SL)

Use of databases to identify the locus of a human gene and its polypeptide product

• Following the sequencing of the whole human genome, we now know the exact locus (position) of every gene across the 23 pairs of chromosomes
• Online databases have been built that are able to locate any known gene or allele
• Anyone can access these loci
  • One example is the European Molecular Biology Laboratory database (EMBL)

• Examples of genes that can be located are
  • The CFTR protein, critical to cystic fibrosis, on chromosome 7
  • HBB, a faulty allele of which is the cause of sickle-cell anaemia, on chromosome 11

• If we know the locus of a particular gene, medicine can establish the location of a faulty allele, which is often recessive
  • A faulty allele can be cut out of the chromosome by genetic engineering using recombinant DNA technology
  • Replacing a faulty allele could lead to genetic therapy
  • Location databases of cancer-related genes are often vital information to researchers, doctors and patients involved in cancer genetics

Use of a database to determine differences in the base sequence of a gene in two species

• The Genbank® database is another that can be used to search for DNA base sequences
  • Uses a computer data analysis technique called BLAST (Basic Local Alignment Search Tool) to spot and 'line up' similar base sequences

• A protein common to all organisms is cytochrome C
• This makes its gene sequence a good one to compare between organisms
• The sequence is available for many different organisms across all three domains
• This gives important information about evolutionary relationships between organisms

The use of databases to compare base sequences (and protein sequences) between species