investigating diversity Flashcards
(13 cards)
what are the two methods of classification?
frequency of measurable or observable characteristics
genetic comparisons
what is the method of comparing observable characteristics based on?
the fact that each observable characteristic is determined by a gene or genes (with environmental influences)
what is a limitation of using observable characteristics to investigate diversity?
a large number of characteristics are coded for by more than one gene- polygenic
characteristics can also be modified by environment
for these reasons, inferring DNA differences from observable characteristics has now been replaced by directly observing DNA sequences themselves- made possible by advances in gene technology
what are the three methods of genetic comparisons?
-comparison of DNA base sequences
-comparison of mRNA base sequences
-comparison of amino acid sequences in specific proteins, encoded by DNA and mRNA
why are we able to compare DNA base sequences to investigate diversity?
when one species gives rise to another species during evolution, the DNA of the new species will initially be very similar to that of the species that gave rise to it
due to mutations the sequences of bases in the DNA of the new species will differ to that of old species
so over time more and more mutations occur and more differences in DNA
what would we expect to find when comparing DNA base sequences for species that are more closely related?
more similarity in base sequence than those that are more distantly related
what is the old and new method for comparing DNA?
old- DNA hybridisation
new- comparing base sequences using modern tech
what is the basic principle of DNA hybridisation?
mix DNA from 2 different species,
allow strands of DNA to combine once helix unwinds, then separate again to see how tightly strands attached
more H bonds means more similar base sequences
what is the problem with comparing sequence of bases in mRNA?
it doesn’t include introns
why may it be better to compare base sequences of mRNA and DNA rather than amino acid sequences?
identifies silent mutations because the code is degenerate, meaning some amino acids can be coded for by the same triplet of bases
how can we use the sequence of amino acids to investigate diversity?
the sequence of amino acids in proteins is determined by a gene
the degree in similarity in the amino acid sequence of the same protein will therefore reflect how closely related species are
what is a method for comparing proteins between species?
immunological comparisons
what is the basic principle behind immunological comparisons?
the more similar the protein (so more similar aa sequence) , the less likely the white blood cells of another species will be to produce antibodies to agglutinate it
