Topic 4.7 - Investigating Diversity

Question 1

How can genetic diversity within or between species be measured? (4)

Answer 1

1) Comparing frequency of measurable or observable characteristics

2) Comparing base sequence of DNA

3) Comparing base sequence of mRNA

4) 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 (3)

Answer 2

1) More differences in sequences -> more distantly related / earlier common ancestor

2) As mutations build up over time

3) More mutations cause more changes in amino acid sequences

Question 3

Explain the change in methods of investigating genetic diversity over time (2)

Answer 3

1) 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

2) 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 (5)

Answer 4

1) Collect data from random samples -> to remove bias
- Use a grid
- Use a random number generator to obtain random coordinates

2) Use same method of measurement each time

3) Use a large sample size / measure a large number of organisms -> so representative of population

4) Calculate a running mean and sample until number becomes constant

5) Ensure sampling is ethical -> must not harm organism and release them unchanged

Question 5

Explain how data should be processed and analysed when investigating variation within a species quantitatively (4)

Answer 5

1) Calculate a mean value of collected data and standard deviation of that mean
- Mean = sum of values in data set / number of values in data set

2) SD shows spread of values about the mean -> higher SD = higher variation

3) If standard deviations overlap, causing values of 2 sets of data to be shared, any difference between the 2 may be due to chance / not significant

4) Use statistical test
- To analyse whether there is a significant difference between populations