26.5 molecular clocks

Question 1

molecular clock

Answer 1

a “yardstick” for measuring the absolute time of evolutionary change based on the observation that some genes and other regions of genomes appear to evolve at constant rates

Question 2

assumption of molecular clock in orthologous genes

Answer 2

–assume the # of nucleotide substitutions in orthologous genes is proportional to the time that has elapsed since they diverged from the common ancestor

Question 3

assumption of molecular clock in paralogous genes

Answer 3

the number of nucleotide substitutions is proportional to time since the genes became duplicated

Question 4

King and Jukes formulated the ___ theory

Answer 4

the neutral theory:

Question 5

what s the neutral theory

Answer 5

it says that most of the change in genes and proteins have no effect on fitness, so does not go through natural selection

• depends on how important a gene is. - if the amino sequence exactly is needed, most changes will be harmful
• if its not that important, fewer will be harmful