Midterm #1 Review
Tuesday, January 28, 2014 11:43 PM
Evidence of Evolutionary change
-Evidence from living species of evolutionarychange.
- Vestigial organs eg. Fish evolvesinto a cave form but still has the bones needed to hold an
eye. Parasitic plant get food from oak tree, thereforedoesn't need photosynthesis,but still
has chloroplastswith genome. Or vestigialization of attractivetraits in small flowering plants
EXP: Doubleday & crew hypothesized that the smaller plants above do not need to grow very tall,
moths eat leaves so smaller plants do not give off aroma since they do not need moths to pollinate
due to self-fertilization. These selfers only have only half the amount of chemicals produced.
Production of these chemicals controlled by a few genes. Therefore floral scent has become
-Evidence from fossil record
- Extinction provides rich record of species
- Succession of living species with fossils in the same region related and distinct from other
- Transitional forms in the fossil record, but not necessarily direct lines of descent
EXP: Darren Irwin: Ring species, warblers
At the blue and red the species no longer recognizes the other as the same species. This is a
circular ring species.
The birds' song changes in a gradual fashion even though they are close together geographically. In
the nuclear DNA the points that are further away are more genetically different which can be seen the nuclear DNA the points that are further away are more genetically different which can be seen
the red and blue populations, same with the mitochondrial DNA This all supports that the birds
have speciated on the two different ends of the ring.
-Homologyof traits: structural and developmentalhomology,molecularhomology,the universality
of the genetic code (4 nucleotide base pairs), pseudogenes and genetic flaws
-Pseudogenes distributed in different organisms is compelling evidence of relatedness
Mechanisms of Change
- Mutation: creates new genetic variation
- Genetic drift: random fluctuation in allele frequencies
- Gene flow: mixing between populations
- Natural selection:nonrandom changes in allele frequencies- Darwin
Natural selectioninspired by amazing results of artificial selection (crop plants,
Phylogeneticsnow used widely in all areas of bio and medicine EXP: hypothesized that there is a lack of pollinators that cause the transition of coastal dune plant
from large to small flowers, population got hammeredby a parasite which eats the developing
anthers. Mitochondrial DNA sequence of larvae analyzed. Found that the moth is rare in
populations where the dune plant is selfing HIV ORIGINS
HIV subtype B originated in Haiti (from Africa) in 1950sand moved to North America in 60s.
Phylogeny and forensics
Intentional infection with HIV
HIV evolvesso rapidly, it forms its own phylogenetic tree inside the patent. It can be tracked
because these phylogenies will nest into each other.
Case study: Did Dr. Schmidt intentionally inject Janet Trahan with HIV-infected blood?
The Wedge Strategy
Legal action on school curricula
Publicity and opinion-making
Irreducibly complex biochemicalpathway, disproved by evolution
Blood clots: duplication of other genes and selection yielded all clotting factors
Clear genetic relations among clotting factor
Mutation accumulation experiments estimate the rate and effect of mutations
- Start with an ancestral genotype
- Have multiple independent lines
- Single-individual descent
- Minimize mortality and selection
- Measure change in mean and variance of fitness across generations
- Want to estimate:U = mutations/genome/generation
S= the effect of the average mutation
EXP: Terumi Mukai mutation accumulation experiment with Drosophila melanogaster
A male fly with a “buff” chromosome is mated with a female holding an balancer (black)
chromosome which carries a phenotypic marker that allows the researcher to determine
when the male has this balancer chromosome.
After the first generation, one male progeny with the balancer is mated with a new After the first generation, one male progeny with the balancer is mated with a new
female (same genotype as their mother) to produce several male offspring, each of which
will start an independent line. One male from each “line” is randomly selected to
continue mating to produce offspring each generation; the fitness of the males selected
from each line are measured, and the average effect of the accumulated mutations on
their fitness calculated.
A male and one of his sisters (also carrying the "buff" and balancer chromosomes) are
also mated every 10 generations to determine the ratio of offspring. If the ratio is ~2/1
(homozygous black is conditional lethal, so we'll only see heterozygotes and homozygous
"buff"), then all offspring which can survive are surviving and the Mendelian ratio is
satisfied; nothing interesting is happening. If the ratio is >2/1, then the yellow