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74 Cards in this Set
- Front
- Back
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mutation
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-any change in the base sequence of DNA
-raw material of evolution --> leads to variation |
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point mutation
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-base-pair substitution; change in a single nucleotide
-caused by chance error during repair -creates new alleles |
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chromosome inversion
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-flipping of a chromosome segment
-breaks in DNA caused by radiation -alleles are locked --> alleles inside the inversion are likely to be transmitted together, as a unit |
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gene duplication
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-additional copy --> unequal crossing over; "extra gene" --> selection -->new function for extra gene
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polyploidy
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-increase in chromosome number; addition of a complete set of chromosomes --> caused by errors in mitosis & meiosis --> new species
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sickle-cell anemia
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-effects human hemoglobin (Hb)
-classic example of a point mutation; single amino acid change -Normal Hb at position 6 = glutamic acid -Sickle-cell Hb at position 6 = valine -normal allele --> adenine at nucleotide 2 -mutant allele --> thymine at nucleotide 2 |
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Point mutation (transition)
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substitute a purine for a purine (A + G) or substitute a pyrimidine for a pyrimidine (C + T)
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Point mutation (transversion)
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-substitute a purine for a pyrimidine or vice versa
-can change the codon read; sickle-cell anemia for example |
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Change in 1st or 2nd position of a codon
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almost always has an effect (changes amino acid)
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Change is 3rd position of a codon
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usually doens't have an effect (usually does not change amino acid)
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Replacement (Non-Synonymous) Substitution
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-point mutations that result in amino acid change
-associated with natural selection |
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Silent (Synonymous) Substitution
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-neutral change
-no effect on phenotype |
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loss-of-function mutation
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-loss of protein product --> loss of function --> new phenotype
-under estimate --> 10% of all gametes have new mutation |
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Mutation Rates
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-Majority of all offspring carry at least one new allele
-Mutation is variable |
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Variation among individuals
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-alleles of DNA polymerase (enzyme involved in DNA replication); error rate varies among individuals
-alleles involved in repair of damage vary |
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Variation among species
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long lived species tend to accumulate mutations
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Variation among genes
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-coding genes (less mutations)
-non-coding genes (more mutations since body uses less of these genes) |
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gene duplication
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-unequal crossing over
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redundant sequence
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-associated with gene duplication
-free to accumulate mutation --> change in function |
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For populations to evolve
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mutations must first be introduced to cause nucleotide differences from which changes arise
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Do new alleles persist over others?
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the appearance of new alleles is no guarantee that they will persist over others
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Will mutated genes transmit to the next generation?
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There is no certainty that mutated genes will transmit to the next generation
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How do mutations persist?
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-Selection
-A random change in the DNA sequence of a species can lead to a new characteristic that may be beneficial to the species -This gives members of a population a distinct advantage over members without the characteristic and the feature is then selected for |
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Chromosomal Inversion
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radiation --> breakage --> fragment of DNA flips
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Supergene
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segments of DNA that are inheirited together
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Polyploidy
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-common in plants & fish
-mechanism for speciation --> new phenotype |
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Mutation leads to
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Mutation --> variation --> diversity (lots of it)
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Fitness & Selection
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measured by the number of descendants produced by one genotype compared to those produced by another genotype
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Mutation + Selection
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-mutation by itself is usually not a potent enough force for evolution
-mutation + selection is key for evolution -mutations are deleterious, but selection works to get rid of them |
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delta-32/delta-32
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resistant to all strains of HIV
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+/+
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vulnerable to HIV
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+/delta-32
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resistant to some strains of HIV
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mutation-selection balance
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mutation happens and selection works to get rid of it
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Genetic Drift
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-random chance
-effects finite, small populations |
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Generation of Variation
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mutation --> random
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Natural Selection
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-dominant mechanism of Evolution
-not random --> adaptation |
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Founder Effect
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-sampling error
-small population moves to new niche -only a segment of the original population is carried on to next population -reduces genetic diversity -leads to random fixation of alleles --> decrease in diversity & evolutionary mechanisms no longer work -eventually, loss of heterozygosity |
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Inbreeding
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-leads to inbreeding depressing --> decrease in fitness of individual or population --> exposure to deleterious alleles
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Evolution of Sex
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Recombination
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Asexual Reproduction
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-mitosis
-maternal genotype preserved -lots of offspring -energy efficient -no loss of genetic info |
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Sexual Reproduction
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-need 2 individuals
-maternal genotype lost -meiosis -loss of genetic info -few offspring -energy inefficient -variation |
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Sampling Error
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-Discrepancies between theoretical expectations and actual results
-genetic drift is an example of sampling error because it causes unexpected changes in the allele frequency by blind luck |
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Red Queen Hypothesis
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environment is constantly changing, so populations must continue to change in order to stay in place
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Theories for Sex
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Theory 1
-short term gains to buffer against extinction -variation -Red Queen Hypothesis & Rice's Ratchet Theory 2 -long term benefits -DNA repair -Berstein: deleterious alleles can be masked in sexual repro, but not in asexual repro -Mueller's Ratchet: Purge defective DNA from lineage; mutations are bound to happen and only way to get rid of them is through recombination which evolved for DNA repair (and as a side result variation developed) |
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Male vs. Female Gametes
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Male
-small, many, built for dispersal, low energy investment Female -large, contain nutrients, high energy investment to make eggs |
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Sexual Selection
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-differential selection pressures on males & females
-Reproductive strategies -males: obtain access to female -female: mate choice (want good genes) |
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Random Fixation (example)
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-Collard Lizards (Missouri)
-lizards are being transplanted from large populations into small populations to increase gene pool & diversity |
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Founder Effect (example)
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-Silvereye birds in Australia
-farther they move, the less genetic diversity there is |
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Neutral Theory
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advantageous mutations are exceedingly rare and most alleles of most genes are selectively neutral
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Migration (example)
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-the movement of alleles between populations
-breaks Hardy-Weinberg rules -changes allele frequencies |
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Effects of migration, drift, and nonrandom mating on Hardy-Weinberg
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-all violate Hardy-Weiberg
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Hardy-Weinberg
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-No selection: all members survive at equal rate & contribute to gene pool
-No mutation: no new alleles -No migration -No chance events: no blind luck -Random mating |
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mutation (example)
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-Water Snakes on Mainland and islands of Lake Erie
-Selection = banded on mainland, unbanded on islands -Migration of banded snakes to island bring their alleles to gene pool -evolutionary mechanism that opposes natural selection -prevents island population from becoming fixed for unbanded alleles |
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Population size on genetic drift
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-sampling error diminishes and sample size increases
-Genetic drift is a powerful evolutionary mechanism on small populations, but power declines in larger populations |
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Lynn Margulis & Dorian Sagan ideas about Sex
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-DNA repair is only function of sex
-Earth Earth --> DNA repair mechanism --> Photosynthesis & ozne -Variation develops as unintended consequence (secondary adaptation) |
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Selectionist Theory
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-advantageous mutations are common enough that they cannot be ignored
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Mutation & Selection on Hardy-Weinberg
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-Violate Hardy-Weinberg rules since selection is nonrandom and mutations introduce new alleles
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Differential Reproductive success in Newts
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-most females mated more than once
-some males did not mate at all (males need females for success) |
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Behavioral Consequences of Differential Reproduction
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-male reproductive success --> limited by access to mates --> competition
-females reproductive success --> limited by capacity to make new offspring --> choice in mate |
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Competition (male vs. male)
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1)monopolize resources to get female
2)Direct control of a female |
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Trade-offs for reproductive success
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-optimal for iguanas to be small, but males are large in order to compete with other males for mates and reproduce
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Sperm Competition
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Mediterranean Fruit Flies that were raised around other males had sperm that would compete
-large ejaculates containing many sperm -deposit a copulatory plug |
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Infanticide
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-Lions kills off all cubs that are not genetically related in order to have their genetic line be the most dominant
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Barn Swallows (Female Choice)
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Hypothesis: long tails favorable
Experiment -44 males 1)Shortened tail feathers 2)mock alteration (took feather off & put it back on) 3)nothing done 4)elongated tails -Outcome: swallows with elongated tails seemed to have advantage |
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Examples of Females Choosing better genes
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1) Argentinian Tree Frog
-Experiment showed that females chose males with longer calls (must be related to better genes) -Eggs fertilized by long call males had somewhat better chance of survival over those fertilized by short call males 2)Hanging Flies -females choose males that can catch larger insects which are displayed outside of their nests to attract females |
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John Roughgarden
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-claims that Darwin's sexual selection only leads to gender stereotypes
-Social Selection --> female choice is an incorrect assumption that females choose mates based on genes -ex. Wrasse --> females choose mates based on which mate will stay on the nest longer & not based on size -ex. Female copulates with multiple mates --> all males protect, forage, etc. because they do not know if it is their offspring or not |
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Altruism
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-one individual pays a fitness cost in order for another individual to receive a fitness benefit
-example = kin selection |
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Kin selection
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-individual will sacrifice time and energy in order to help family members reproduce & survive because family genes will be passed on even though the individual is not actually reproducing
-Give up personal fitness to help genetically related individuals survive and reproduce -sterile worker honey bees expend time & energy to improve fitness of genetically related individuals -Recipient benefits directly from kin selection, while the actor may have to sacrifice life -However, in the overall scheme, both benefit because they are having their genes passed on to future generations |
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Non-zero Sum Game
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-one that is mutually beneficial to both players
-Husband & Wife |
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Zero Sum Game
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-there is a winner and a loser
-any sporting event under normal circumstances |
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Nasty strategy
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-defects first
-Always defect |
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Nice strategy
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-never defects first
-Tit-for-Tat |
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Apoptosis
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-Cell suicide
-prevents accumulation of unneeded or defective cells |
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Do apoptosis & gene stability networks have the same evolutionary origins?
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-No, they do not have the same evolutionary origins
-Genome stability network emerged first |
