9.3 Flashcards
(9 cards)
What are the 4 different ways of genetically comparing 2 organisms? (4)
(1) DNA Hybridisation / DNA base sequencing
(2) Genome sequencing
(3) comparing amino acid sequences in proteins
(4) immunological comparisons of proteins
When a species gives rise to another species during evolution, will the DNA of the new species be different or very similar? (1)
Very similar
Why do new species accumulate more and more differences in their DNA overtime? (2)
(1) due to mutations,
(2) so the sequences of nucleotide bases in the DNA of both species will change
Describe the process of DNA hybridisation / DNA base sequencing. (9)
(1) DNA from 2 species is extracted
(2) DNA from 1 of the species is labelled by attaching a fluorescent marker to it
(3) it’s then mixed with the unlabelled DNA from the other species
(4) the mixture of both DNA is heated to separate their strands
(5) the mixture is cooled to allow the strands to combine with other strands that have a complementary sequence of bases
(6) some of the double strands that reform will be made up of one strand from each species
(7) the new strands are hybrid strands ; they can be identified because they’re 50% labelled
(8) the hybrid strands are separated out & the temp is inc. in stages
(9) at each temp stage, the degree to which the 2 strands are linked together is measured
If the 2 species being compared are closely related, explain what the DNA hybridisation/ DNA base sequencing results would show. (4)
(1) many complementary nucleotide bases are shared
(2) so there are more hydrogen bonds (between the complementary bases)
(3) so the hybrid strand is stronger
(4) the stronger the strand is, the higher the temp. needed to separate it.
What is the goal of genome sequencing? (1)
(1) to determine precisely the species present without the need to isolate and culture each individual species
How does genome sequencing work? (3)
(1) genome sequences of known organisms are stored on a database
(2) so the DNA of an unidentified organism is compared to the known organisms to classify it
(3) because if their DNA is greatly similar, it means they’re closely related in evolutionary terms
Why are amino acids used to compare how genetically similar 2 species are? (2)
(1) the sequence of amino acids = determined by DNA
(2) the degree of similarity in the AA sequence of the same protein in 2 species reflects how closely related the 2 species are
How are immunological comparisons of proteins used to measure the degree of similarity of 2 species? Use species A, B & C for the method (7)
(1) a protein from species A is injected into species B
(2) species B produces antibodies specific to all the antigen sites on the protein from species A
(3) the serum is extracted from species B, which contains the antibodies produced
(4) the serum is mixed with serum from species C
(5) the antibodies respond to their corresponding antigens on the proteins in the serum of species C
(6) the response is the formation of a precipitate
(7) the greater the number of similar antigens, the more precipitate is formed & the more closely species A & C are related
