4.7 Investigating diversity Flashcards
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 how data should be collected when investigating variation within a
species quantitatively
● 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
Explain how data should be processed and analysed when investigating
variation within a species quantitatively
● 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
Deletion:
form of gene mutation in which one or more nucleotide bases are removed from a DNA sequence. This may change all amino acids in a sequence,
Universal
A feature of the genetic code; the code is the same in almost all organisms
Non-overlapping
A feature of the genetic code; each base in a sequence is read once and is only part of one triplet.
Non-disjunction
A change in the number of chromosomes due to the failure of homologous chromosomes to separate during meiosis. This may result in a gamete with one more or one less chromosome.
