[10.4] investigating diversity

Question 1

in what ways can genetic diversity be compared within, and between species? (4)

Answer 1

• observable characteristics
• DNA base sequences
• mRNA base sequences
• amino acid sequences in proteins

Question 2

what is the method of comparing observable characteristics based on?

Answer 2

• the fact that each observable characteristic is determined by a gene or genes, with environmental influences
• the variety within a characteristic depends on the number and variety of alleles of that gene

Question 3

what are the limitations of using observable characteristics?

Answer 3

• a large number of observable characteristics are coded for by more than one gene (polygenic)
• often difficult to distinguish one from another
• characteristics can be modified by the environment

Question 4

what is genome sequencing?

Answer 4

• it involves reading the entire base sequence of different organisms and comparing them
• or looking at base sequences of conserved genes (from respiration)
• closer related species will have very similar base sequences

Question 5

why do closer related species have more similarity in their DNA base sequence?

Answer 5

• when one species gives rise to another, the DNA of the new species will initially be very similar to other species
• due to mutations, the sequences of nucleotide bases in the DNA of the new species will change
• over time, the new species will accumulate more and more differences in its DNA
• as a result, we would expect species that are more closely related to show more similarity in their DNA base sequences than species that are more distantly related

Question 6

comparison of the base sequence of mRNA

Answer 6

• mRNA is coded for by DNA
• base sequences on mRNA are complementary to those of the strand of DNA it was made from
• we can measure DNA diversity, and therefore genetic diversity, by comparing the base sequences of mRNA

Question 7

comparison of amino acid sequences in proteins

Answer 7

as base sequences code for amino acids, similar organisms with similar base sequences will have similar amino acid sequences in their proteins

Question 8

why are good proteins for comparison needed?

Answer 8

• organisms within the same species have genes that produce very different proteins (eg. eye colour) so this wouldn’t be a good protein for comparison
• therefore, scientists compare proteins that come from highly conserved genes, eg. cytochrome c, a protein found in many species for respiration

Question 9

comparing immunological responses

Answer 9

organisms with similar DNA base sequences have similar amino acid sequences, bonds in similar places and similar tertiary structure proteins

Question 10

how can you compare immunological responses?

Answer 10

• take a conserved protein from a human and a chimpanzee
• add monoclonal antibody that form an antigen-antibody complex to human protein to both
• if they have very similar tertiary structure proteins, the antibodies will bind similarly and form a similar mass of precipitate