4.7 - Investigating Diversity

Question 1

how can genetic diversity within or between species be measured?

Answer 1

-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

Question 2

explain how comparing DNA, mRNA and amino acid sequences can indicate relationships between organisms within a species and between species

Answer 2

• 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

Question 3

explain the change in methods of investigating genetic diversity over time

Answer 3

• 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

Question 4

explain how data should be collected when investigating variation within a species quantitatively

Answer 4

• collect data from random samples → to remove bias
  ○ use a grid / divide area into squares
  ○ use a random number generator to obtain random coordinates
• use same method of measurement each time
• use a large sample size / measure a large number of organisms → so representative of population
• calculate a running mean and sample until number becomes (fairly) constant
• (where applicable) ensure sampling is ethical → must not harm organism / must allow release unchanged

Question 5

explain how data should be processed and analysed when investigating variation within a species quantitatively

Answer 5

• calculate a mean value of collected data and standard deviation (S.D) of that mean
  ○ mean = sum of values in data set / number of values in data set
• 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
• use [named] statistical test
  ○ to analyse whether there is a significant difference between populations