4.7 Investigating diversity

• How can genetic diversity within or between species be measured?

  • ● Comparing frequency of measurable or observable characteristics
  • ● Comparing base sequence of DNA
  • ● Comparing base sequence of mRNA
  • ● Comparing amino acid sequence of a specific protein encoded by DNA and mRNA
• Explain how comparing DNA, mRNA and amino acid sequences can indicate relationships between organisms within a species and between species

  ● More differences in sequences → more distantly related / earlier common ancestor

  ● As mutations (change in DNA base sequences) build up over time

  ● More mutations cause more changes in amino acid sequences
• Explain the change in methods of investigating genetic diversity over time

  • ● Early estimates made by inferring DNA differences from measurable or observable characteristics
  • ○ Many coded for by more than one gene → difficult to distinguish one from another
  • ○ Many influenced by environment → differences due to environment not genes
  • ● Gene technologies allowed this to be replaced by direct investigation of DNA sequences
• Explain the key considerations in quantitative investigations of variation within a species part 1

  • ● Collect data from random samples (use a random number generator) → removes bias
  • ● Use large sample size (or sample until stable running mean) → representative of whole population
  • ● Ethical sampling (where applicable) → must not harm organism / allow release unchanged
  • ● Calculate a mean value of collected data and standard deviation of that mean
  • ● Use [named] statistical test → analyse whether there is a significant difference between populations
• Explain the key considerations in quantitative investigations of variation within a species - part 2 mean + SD

  ● Interpret mean values and their standard deviations (S.D)

  ○ S.D shows spread of values about the mean → higher S.D = higher variation

  ○ If standard deviations overlap, causing values of two sets of data to be shared, any difference between the two may be due to chance / not significant