INVESTIGATING DIVERSITY

• INVESTIGATING DIVERSITY WITHIN / BETWEEN SPECIES

  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
• COMPARISON OF DNA BASE SEQUENCES

  • this is bc DNA determines the proteins if an organism which in turn determines features of an organism
  • changes In features of an organism are due to changes in the dna. Therefore comparing the DNA of different species helps scientists to determine evolutionary relationships between them
  • when speciation occurs, initially two species will be very similar. Mutations will cause the sequences of nucleotide bases in the DNA to change + overtime as the different species are subjected to different selection pressures, the DNA becomes more + more different.
• COMPARISON OF DNA BASE SEQUENCES

  Species with more similar DNA are more closely related than those with less similar DNA
• INTERPRET DATA

  • interpret data relating to similarities and differences in the base sequences of DNA and in the amino acid sequences if proteins to suggest relationships between different organisms within a species and between species
• CHANGE IN GENETIC DIVERSITY INVESTIGATION

  GENETIC DIVERSITY: the total number of different alleles of genes in a species or population. The differences in DNA.

  - early estimates of genetic diversity were made by looking at the frequency of measurable or observable characteristics in a population. Since different alleles determine different characteristics, a wide variety Of each characteristic in a population indicates a high number of different alleles, so a high genetic diversity.

  - During speciation (one species gives rise to another species during evolution) the DNA of the new species will initially be very similar to that of the species that gave rise to it. Due to mutations, the sequences of nucleotide bases in the DNA of the new species will change. Consequently, over time, the new species will accumulate more + more differences in its DNA. As a result, we would expect species that are more closely related to show more similarity in their DNA base sequences than species that are more distantly related.

  - As there are millions of base sequences in every organism, DNA contains a vast amount of information about the genetic diversity and evolutionary history or all organisms

  - We now use gene technology to measure genetic diversity directly by comparing sequences (DNA, mRNA, AA). These new technologies can be used to give more accurate estimates of genetic diversity within a population (or species) than can be made by just looking at the frequency of observable characteristics. They also allow the genetic diversity of different species to be compared more easily.
• COMPARING OBSERVABLE CHARACTERISTICS

  Linnaeus used observable features to classify organisms

  - this method is based on the fact that each observable characteristic is determined by a gene or genes (with environmental influences). The variety within a characteristic depends on the number + variety of alleles of that gene (+ environmental influences)

  - using observable characteristics has limitations bc a large number of them are coded for by more than one gene (polygenic). It's often difficult to distinguish one from another. Characteristics can also be modified by environment.

  - differences may therefore be the result of different environmental conditions rather than different alleles
• COMPARING AMINO ACID SEQUENCE IN PROTEINS

  - proteins made of amino acids. Sequence of amino acids determined by mRNA which in turn is determined by DNA

  - Genetic diversity within + between species can be measured by comparing amino acid sequences of their proteins

  - related organisms have similar DNA sequences + so similar amino acid sequences in their proteins. The degree of similarity in the amino acid sequence of the same protein in 2 species will also reflect how closely related the 2 species are

  - once the amino acid sequence for a chosen protein has been determined for 2 species, the 2 sequences are compared. This can be done by counting either the number of similarities or the number of differences in each sequence

  - bigger degree of similarity = more closely related