4.7 Investigating Diversity

• Genetic diversity within, or between species, can be investigated by comparing:

  • The frequency of measurable or observable characteristics.
  • The base sequence of DNA.
  • The base sequence of mRNA.
  • The amino acid sequence of the proteins encoded by DNA and mRNA.
• What are genetic comparisons used to do?

  They're used to discover the evolutionary relationships between organisms and as a basis for classification systems. The more similarities the more closely related they are.
• How did we compare species in the past?

  We used to compare the similarities and differences of species features/characteristics and how frequently these were occurring e.g.

  • Comparing anatomy (bone/wing structures).
  • Compare physiological features.
• How do we compare species today?

  1. Using DNA base sequences: we compare the same gene so we will have some bases in common. DNA allows us to compare bases, triplets and introns between bases which is the advantage of studying DNA base sequences over mRNA sequences as introns have been spliced out in mRNA.
  2. Amino acid sequences. Select a protein present in all the organisms investigated e.g. haemoglobin. Within the same protein, compare the amino acid sequence.
• What is the immunological comparison of proteins based on?

  It's based on antibody-antigen specificity
• The Immunological comparison of proteins

  If antigens from one species are similar to antigens from another species, then antibodies formed in response (in the immune system of a mouse, rat or rabbit) will fit both.
• The Immunological comparison of proteins

  If antigens in a sample of blood, bind to antibodies in a serum that is mixed with the blood, then precipitation occurs upon centrifuging.