3.4.7 Investigating diversity

• The link between DNA and the tertiary structure:

  A) triple

  B) DNA

  C) gene

  D) exon

  E) transcription

  F) codon

  G) mRNA

  H) translation

  I) amino

  J) primary

  K) R-group

  L) bonds

  M) ionic

  N) hydrogen

  O) disulphide

  P) tertiary

  
• Different ways to classify organisms:

  • Comparison of observable features- not useful due to polygenetic characteristics.
  • Comparison of DNA base sequences- closely related organisms can be identified and mutations can be seen between distantly-related organisms.
  • Comparison of the base sequence of mRNA.
  • Comparison of the amino acid sequence in proteins.
• DNA sequence can be used to find out the amino acids, but the amino acid sequence can't be used to find out the DNA sequence, because of the degenerate code.
• DNA hybridisation:

  • Sections of DNA are used- whole strands are too long.
  • Heat is used to separate and mix the two strands- forming a hybrid.
  • The level of hybridisation indicates how related they are.
• Complete hybridisation- organisms are identical, they have complementary bases

  
• No hybridisation- organisms are unrelated, they have no complementary bases

  
• The early days of estimating genetic diversity:

  • Scientists observed visual features in a population and the number of organisms with that particular feature.
  • Different alleles determine different characteristics, so a wide variety of each characteristic indicates high allele numbers and genetic diversity.
• Gene technology can now measure genetic diversity directly:

  • Different alleles of the same gene have slightly different DNA base sequences which can be compared within individuals in a population to identify the number of those gene alleles.
  • Different alleles produce slightly different mRNA base sequences and proteins with slightly different amino acid sequences- which are easy to compare.
• Gene technologies can get more accurate estimates of genetic diversity within populations/ species than traditional ways of comparing observable characteristics and features.