3.4.7 Investigating diversity ( 3.4 Genetic information , variation and relatoonships between organisms)

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 sequence - more distantly related
• as mutations 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 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 investigations 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
  • use a random number generator to obtain random coordinates
• use same method of measurement each time
• use a large sample size of organisms so its representative of the population
• calculate a running mean and sample until number becomes constant
• ensure sampling is ethical - must not harm organism

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 of the mean
• SD shows spread of values about the mean - higher SD = higher variation
• if SD overlaps , any difference between the two may be due to chance / not significant
• use statistically test
- to analyse whether there is a significant difference between populations