Natural Selection & Speciation Flashcards
Week 32 Quiz
5 factors that signify evolution within a population
- Genetic mutation
- Gene flow (immigration)
- Non-random mating
- Genetic drift (separation of population)
- Selection (predator vs. prey)
Define ‘population’
organisms that interbreed to create fertile offspring
Define ‘gene pool’
A collection of alleles in a population
Define ‘allele frequency’
Commonality of allele; how often it appears
Define ‘evolution’
Major changes in alleles; changes in a population over time
What must be true in order for a population to not be evolving?
- The population is large
- there is no migration/gene flow
- random mating (no sexual selection)
- no natural selection
What does the Hardy-Weinberg Theorem have to do with?
Determining allele frequency
Frequency of homo dominant allele equation
p x p = p^2
Frequency of homo recessive allele equation
q x q = q^2
Frequency of hetero allele equation
pq + qp = 2pq
100% of a population (equation of dominant/recessive traits)
1 = p^2 + 2pq + q^2
Equation that will not be on the test ( = 100% of gene pool)
p + q = 1
Transcription factors are
regulatory genes
Activators in gene expression…
bind to DNA to increase operon (regulatory & structural gene) transcription
When does most gene regulation occur in Eukaryotes?
Transcription during or after RNA/protein production (translation)
Gene Regulation Method 1: Turning on/off access to DNA
limits chromatin accessibility; relaxed chromatin allows for transcription better than not
Gene Regulation Method 2: Switching on/off transcription factors
Activators or repressors turn on/off genes; turn on/off responses to outside information
Define ‘gene expression’
DNA is converted into a functional structure (protein); how cells respond to environment; decides protein production/volume; structure and function
Components of gene expression
Promoter, operator, regulatory genes, transcription factors, repressors
Promoter
Where RNA polymerase binds on DNA to initiate transcription
Operator
DNA segment controlling RNA access to promoter (controlled transcription)
Operon
Promoter + operator + structural genes
Inhibitor/repressor protein
attaches to operator to inhibit transcription (RNA reaching structural genes)
In order for proteins (genes to be expressed) to be made in response to environmental signals…
… RNA polymerase must reach the structural genes
Define ‘genome’
Complete genetic material
Advantage of gene expression
conservation of resources
Why is gene expression different in eukaryotes than prokaryotes
Eukaryotes have bigger genomes, multiple chromosomes, specialized cells, and less operons
Site of transcription in Eukaryotes
euchromatin
Does all of a chromatin strand uncoil?
No, some are fixed and tightly coiled so they can’t be translated
What segments lie beyond the promoter in Eukarotic genes?
Introns (transcribed and not translated (made into a protein))
Exons (transcribed and translated)
On in Eukaryotes, after transcription (that makes pre-mRNA), introns are _____ and exons _____
removes, splice (join) one another to make mRNA
Intron removal from pre-mRNA can be catalyzed by
ribozymes
Transciption factors may still directly control transciption as it occurs by…
placing RNA polymerase on the promoter, or by binding to enhancers that may loop around and touch RNA polymerase and the promoter.
Define ‘cell differentiation’
cells develp with specialized functions; the growth of tissues to produce a characteristical form is called morphogenesis.
Homeotic Genes
position anatomical structures during morphogenesis; translate into regulator proteins that control patters of developmental genes and adjust rates of cell division.
Homeobox Sequence
Homeoboxes (DNA sequence inside homeotic genes) code for protein regulators. Mutations cause developmental abnormalities. Organisms have similar homeoboxes throughout their body.
What do DNA chips do?
Track gene expression by noting complementary linking of mRNA and DNA.
Cell division regulation proteins are coded by
proto-oncogens
Oncogens (mutated proto-oncogens) lead to
over/untimely expressed cell divison proteins
Mutations in tumor supressor genes ______ lead to cancer
Directly
(in comparision to mutations in proto-oncogens, which lead to oncogens, which then lead to cancer)
Cancer capabilities
indefinite divison, neighbor cells unecessary, crowding isn’t a stunt, metastasis
Cancer-causing substance
carcinogen/mutagen
Cancer development risk
Genetic susceptibility and carcinogen exposure
Kinds of cancer
Carcinomans (skin/tissues)
Sarcomas (bone/muscle)
Lymphomas (solid; grow in lymphatic tissues)
Biological fitness
ability to survive and pass on genes; more offspring = more fitness
Natural obstacles
food, water, mating competition; pathogens, disease; predators
Natural Selection
organisms with favorable traits reproduce more; drives evolution; adapts to constant environment; caused by random mutations (positive, negative, neutral)
3 types of natural selection
Directional, stabilizing, diversifying
Directional selection
one extreme is favored
Stabilizing selection
intermediates are favored (mix between two extremes)
Diversifying selection
two extremes are favored (intermediates not favored)
Microevolution
a change in allele frequency that is passed on through mutations in sexual reproduction
Variation occurs by ________ characteristics and __________ characteristics
discrete (one trait or another; extreme), quantative (logged on a continuum)
Define ‘polymorphism’
Two different traits have equal fitness in a population.
average of heterozygous loci
Average heterozygosity
How to find nucleotide variability
compare DNA of two organisms
Geographic variation
difference between gene pools
cline graph
shows changing traits along an axis of locations
What kinds of cells’ mutations are inherited?
Gamete-producing cells’ mutations (germ-line/somatic)
Point mutations only affect
one base in a gene
Mutations in protein production are often harmful
change fitness of organism
Mutations in non-coding DNA are…
harmless
Harmful mutations
delete, disrupt, rearrange loci, diplicate chromosome large parts
Animals and plants have a ______ mutation rate
low (1 in 100k genes)
viruses mutate more
Define ‘population’
interbreeding, offspring producing
Define ‘gene pool’
all alleles of all loci of a population
Mendenlian inheritance laws insure genetic variability
not to be confused with Hardy-Weinberg principle of non-evolving populations
Genetic Drift
unpredictable fluctuation in allele frequencies
Reduces genetic variation thorugh losing alleles
Small gene pools allow for greater deviation
Can make alleles permanent
The Founder Effect
separated individuals can have different allele frequencies
The Bottleneck Effect
Environment causes sudden population reduction and changes the gene pool
The smaller population is then subect to gentic drift
Gene flow
movement of alleles between gene pools through fertile individuals; decreases variation; greater effect on fitness than mutations
Relative fitness
One’s contibution to gene pool compared to others; selection affects phenotypes to favor genotypes (and thus change genotypes)
Why natural selection can’t make perfect organisms
It onyl works on previously existing organisms
Evolution has limits
Adaptations are compromises
Natural selection works with environments, which change
Adaptive evolution
increases survival rate and fitness
Sexual selection
created sexual dimorphism
intrasexual selection: competition for other sex
intersexual selection: one is choosy about other
Diplody
tool in preservation of genetic variation that hides recessive alleles
balancing selection
typical amount of phenotypes present
heterozygotes have an advantage because…
natural selection allows multiple alleles (multuple positive and/or negative attributes)
Frequency-dependent selection
fitness declines as phenotype increases in commonality
Speciation
evolution creates distinct speciesa
allopatric speciation
new species from geographic isolation
Sympatric speciation
new species from single ancestor
Parapatric speciation
new species from partial isolation as new niche enters
divergent evolution
new species from common ancestor
convergent evoltion
similar species from different ancestry in similar environemt
parallel evolution
distinct species with similar traits from a common ancestor
coevolution
effect of two associated species on each’s evolution
analogous structure
structurally and derivatively different but have same function
homologous structure
same basic structure but has different functions
Prezygotic isolation
reproductive barrier stops zygote (geographic isolation or behavioral isolation)
Postzygotic isolation
reproduction battier of zygote
Cladograms
use phylogeny to graph organisms; based on shared derived characteristics
Oldest is at the bottom and descendents branch off.
‘V’ event is where speciation happens.
Clades result from common ancestor groups.
