Exam 2

org evo
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Terms in this set (...)

species
set of interbreeding populations that are reproductively isolated from other such populations
prezygotic isolation
fertilization never occurs (no mating or no fertilization)
postzygotic isolation
fertilization occurs but hybrids have low survivorship or fertility (hybrids don't develop or survive well or are sterile)
allopatric speciation
populations initially isolated by geography
parapatric speciation
populations have ranges that are largely separate but with some overlap
sympatric speciation
populations have greatly overlapping ranges, or one is nested within the other
Haldane's Rule
when isolated populations diverge, post zygotic isolation appears first in the heterogametic sex
epistasis
non additive interactions between genes
reinforcement
selection to not interbreed in order to avoid hybridization (since it leads to low fitness offspring)
peripheral isolate
small population that becomes isolated on the periphery of the parent population range
plants prevent interbreeding by:
-changing flowering time
-changing flower morphology
-preventing pollen tube from developing
mated to extinction
rare phenotypes driven to extinction since most offspring will be hybrids
magic traits
traits that experience disruptive selection and also induce assortative mating
allopolyploidy
polyploidy in a hybrid
polyploidy
the occurrence of one or more extra sets of all chromosomes in an organism
autopolyploidy
polyploidy in non-hybrid genome
topology
pattern of common ancestry
monophyletic group
all and only the descendants of a common ancestor (including that ancestor)
paraphyletic group
does not include all of the descendants of the common ancestor
polyphyletic group
does not include the common ancestor
homology
two traits in two different organisms that are derived through a continuous sequence from the same trait in a common ancestor
derived character states
those not present in the common ancestor of all of the organisms under study
clade
monophyletic group
apomorphy
derived character state
synapomorphy
shared derived state
autapomorphy
possessed by only one group.
plesiomorphy
ancestral character state
symplesiomorphy
plesiomorphy shared by two or more groups
maximum likelihood
choose the tree that, if correct, would maximize the probability of seeing the data that we see
bayesian tree construction
choose the tree that has the highest probability given the data
maximum parsimony
choose the tree that has the smallest number of character state changes on it
gene and species tree will be different if:
time between speciation events is small or there's been balancing selection maintaining polymorphism against drift
incomplete lineage sorting
gene trees do not always match species trees
synonymous changes
base pair changes in a DNA sequence do not lead to any amino acid change
nonsynonymous changes
base pair changes in DNA sequences do lead to an amino acid change
Ka=
number of non synonymous changes in a DNA sequence divided by the total possible number of non synonymous changes
Ks=
number of synonymous changes in a DNA sequence divided by the total possible number of synonymous changes
Ka/Ks=1
gene is neutral; all possible mutations have no effect on fitness
Ka/Ks<<1
purifying selection; most mutations that lead to AA change are selected against
Ka/Ks>>1
directional selection; mutations that cause AA change are being fixed at higher rate than neutral mutations
hitchhiking
genes that are not under selection, but are increasing in frequency because they are near an allele that is being selected for
selective sweep
rapid increase in allele frequency due to selection
gene duplication can occur:
through unequal crossing over
paralogous
genes that are duplicated within a genome
orthologous
genes in different species that evolved from a common ancestral gene by speciation
possible outcomes of gene duplication
- both copies persist and do same thing
- one copy becomes pseudogene
- one copy diverges in function
pseudogene
genomic DNA sequences similar to normal genes but non-functional
divergence after duplication
might produce pseudogene or a new functional gene
divergence during duplication
gene expression influenced by position on chromosome; duplicated gene in new location may cause different expression
divergence before duplication
adaptive to have 2 variants of protein (heterozygote superiority)
ways to get new genes:
mutation
gene duplication
exon shuffling
globin gene duplication event important in mammalian evolution
divergence of gamma globin (allows fetus to extract O2 from mother)
example of divergence before duplication
new world monkeys and trichromatic vision (heterozygous females have trichromatic vision)
exon shuffling
rearranging of parts of existing genes to make new genes emerge
exons
coding DNA; translated to a protein sequence
introns
noncoding DNA; excised from the pre-mRNA
example of exon shuffling
tPA created by adding exon from fibronectin to urokinase (allowing fibrin binding)
DNA transposons
cut themselves out of DNA and move to a new location
retroelements (retroposons)
transcribe themselves, then use reverse transcriptase to copy themselves back into the genome; can carry other genes
types of retroelements
short interspersed elements (SINEs)
long interspersed elements (LINEs)
signs of LINE or SINE insertion:
introns missing
promoter sequence missing
processed pseudogene
promoter sequence missing from gene that was moved via retroelement
retroelement insertions useful for phylogenies because:
1) unlikely same element will insert itself in same spot more than once
2) unlikely element will be deleted or be deleted with no trace
homoplasy
same trait arising more than once
multilevel selection
behavior is result of 2 different selection processes (ex: selection on host and selection on transposable elements influence TEs)
hybrid dysgenesis
low hybrid fitness; problems increase in each crossed generation
example of multilevel selection
p-elements
horizontal gene transfer
transfer of genes between individuals other than parent-offspring transfer
segregation distortion genes
'meiotic drive' genes; produces distortion in normal segregation in favor of itself, so that chromosomes bearing this gene are over-represented in an organism's offspring
hox genes
associated with anterior-posterior positional information in metazoans
bithrorax
mutation that converts halteres in dipterans into 2nd pair of wings
antennapedia
mutation that converts antennae into legs
homeobox sequence
180 bp sequence that encodes for a functional domain that allows the protein to bind to DNA
transcription factors
proteins that bind to DNA and regulate the transcription of other genes
cis-regulatory element (CRE)
short sequence to which a transcription factor binds, usually adjacent to the gene being regulated
Pax-6
codes for eye development; ey gene in drosophilia
MADS box
codes for identity of plant parts; has genes A, B, and C
life history strategies:
- spread out reproduction vs reproduce all at once
- reproduce early and die young vs live a long time and delay reproduction
- produce many offspring each with
low chance of survival vs produce few offspring with high chance of survival
lx
probability of surviving to age x
px
probability of surviving from age x to age x+1
mx
expected number of offspring produced at age x
Bateson-Dobzhansky-Muller (BDM) Model
possible for populations to drift to a point of reproductive isolation without going through fitness valley via epistasis