Investigating diversity Flashcards
Genetic diversity
Number of different alleles in a population
What causes genetic diversity
Mutations of base sequence + chromosome mutation
Random fertilisation
Meiosis - crossing over + independent assortment
Ways of investigating genetic diversity
- the frequency of measurable or observable characteristics
- the base sequence of DNA
- the base sequence of mRNA
- the amino acid sequence of the proteins encoded by DNA and mRNA.
What has helped clarify evolutionary relationships?
Advances in genome sequencing
Advances in immunological techniques
Genome sequencing
Working out the set of genes in an organism because the genome is the complete set of genes (all the dna) in an organism
What does genome sequencing allow us to do?
Compare base sequence of DNA
Compare base sequence of mRNA
Shows differences in alleles thus genetic diversity
So therefore evolutionary relationship
Using genome sequencing to establish evolutionary relationships
Compare base sequences of DNA between different species
Shows different number of alleles = genetic diversity
Between species (variation)
And to different species (evolutionary relationships)
Measuring frequency of observable characteristics for genetic diversity
More variation in characteristics indicates greater genetic diversity
Eg larger number of different alleles that encode for variety of phenotypes
Problems with using observation to measure genetic diversity
Sex differences/lifecycle changes in SAME species may be mistakenly observed as being due to different species
Looking similar doesnt necessarily mean closely related
Environmental factors affect phenotype as well as genetics
Comparing base sequence of DNA of closely related species
Have less differences in base sequence
Comparing base sequence of DNA of less closely related species
Have more differences in base sequence
Comparing amino acid sequence of polypeptide from closely related species
Have less difference in amino acid sequence
Comparing amino acid sequence of polypeptide from distantly related species
Have more difference in amino acid sequence
Why can we use differences in mRNA base sequence/ AA sequence to study relationships between different species?
Imply variations present in DNA
*Which is ultimately the important factor in establishing how closely related species are
Why do distantly related species have more variation in DNA base sequence/ amino acid sequence ?
Mutations change the base sequence of DNA
This causes change in the base sequence of mRNA and so the amino acid sequence of a protein
Mutations build up over time
More mutations in base sequence/more differences in amino acid sequence occur between more distantly related species= earlier common ancestor
Why do closely related species have more variation in DNA base sequence/amino acid sequence
Mutations change the base sequence of DNA;
This causes change in the base sequence of mRNA and so the amino acid sequence of a protein;
Mutations build up over time;
Less mutations in base sequence/less differences in amino acid sequence occur between more closely related species;
More closely related species share a more recent common ancestor
Change in techniques investigating genetic diversity
Improved gene technology means we can directly compare DNA base sequences rather than inferred differences in alleles of DNA from observed characteristics
Does having a high % difference in DNA base sequences necessarily indicate a difference species?
No, may show high intraspecific variation (eg between species)
How can we show the % difference in DNA base sequence is significant enough to be between different species?
Use standard deviation, no overlap = significant enough to be between different species
Phylogenetic classification system
DOmain, kingdom, phylum, class, order, genus, species
Hierarchy with no overlap
Based on evolutionary history
How to ensure quantitative data eg in the form of % differences in base sequences is valid?
Use a large sample to ensure data is representative
Calculate mean and use standard deviation of mean to show if significant % difference or not
Use random samples to avoid bias
Use statistical test
Why is DNA base sequence a better measure of evolutionary relationships than amino acid sequence?
Longer base sequence in DNA than amino acid sequence of proteins so more comparisons possible
Degenerate code means different triplet encodes for same amino acid, so possible differences in DNA base sequence not detected
