Exam 3 Flashcards
Population Genetics
links traits in a population across generations to changes in the frequency of alleles
What is an ideal population?
idea of what happens with alleles and genotypes frequencies
-reference point
gametes are haploid or diploid?
haploid
zygotes are haploid or diploid?
diploid
what make evolution occur unpredictably?
due to blind luck of allele combinations
who invented punnett squares?
Reginold Crundall Punnett
what do punnett squares predict?
the genotypes in offspring for an ideal population
what do punnett squares remove when predicting genotypes?
blind luck (random chance)
when are frequencies in equilibrium and what does that mean for evolution?
when frequencies don’t change from generation to generation
-population does not evolve
what did Godfrey Hardy do for punnett squares?
used statistics to prove that allele frequencies don’t change from generation to generation
what are the three conclusions of the Hardy-Weinberg equilibrium?
-allele frequencies will not change from generation to generation
-if allele frequencies in population are given by p and q, the genotype frequencies will be given by p^2, 2pq, q^2
what does p in the H-W equation represent?
allele frequency of the dominant allele
what does q in the H-W equation represent?
allele frequency of the recessive allele
what does p^2 in the H-W equation represent?
homozygous dominant genotype
what does q^2 in the H-W equation represent?
homozygous recessive genotype
what does 2pq in the H-W equation represent?
heterozygous genotype
what are the five assumptions of the H-W principle?
-no selection
-no migration
-no chance events
-no mutation
-individuals choose their mate at random
what does having no selection, no migration, no chance events, and no mutation effect? (allele or genotype frequency)
allele frequency
when individuals choose their mate at random, what does it effect? (allele or genotype frequency?
genotype frequency
does the H-W equilibrium occur in nature?
no
H-W equilibrium provides an ____ that we can compare to
ideal baseline
what are the four processes that drive evolution?
-migration
-mutation
-genetic drift (random selection of alleles)
-selection (things die)
what is selection?
individuals with particular phenotypes survive and reproduce more than others
how does selection make evolution occur?
changes allele frequencies by increase proportion of heterozygous genotype
what is positive selection?
increase frequency of favorable allele
what is negative selection?
decrease frequency of harmful allele
what is the difference between a fixed and lost allele?
fixed: all have it
lost: none have it
which type of allele (dominant or recessive) is rare to make natural selection occur fast?
dominant is rare
-recessive is common
what happens to rate of natural selection when the recessive allele is rare?
natural selection occurs slowly
what is heterozygosity?
when a lethal recessive allele doesn’t entirely disappear from a population due to the recessive allele “hiding” in heterozygotes
what is overdominance?
when heterozygotes have a higher fitness than homozygotes
-allele frequencies don’t change
-good
what is underdominance?
when homozygotes are more fit than heterozygotes
-leads to allele fixation and the other allele being lost
-not good
what is frequency dependent selection?
favoring the more rare trait until it becomes common and then switching back to the other trait that is now rare
-EX: bees like rare flowers (bee goes to rare purple flower, purple flower becomes common so it switches to the now rare yellow flower that used to be common but no longer is)
what is mutation?
error in coping that alters frequency of alleles
does mutation have a big impact on a population overall?
no, it makes small changes
-small changes can be built up to make big impacts in the future though
-when harmful/deleterious they are eliminated by selection
what is the mutation-selection balance?
the rate at which harmful alleles are removed by selection equal the rate at which new harmful alleles are created by mutations
what happens to mutation rate when there is a high selection rate?
creates a low mutation rate
what happens to selection rate when there is a high mutation rate?
creates a low selection rate
what is conservation population genetics and what three things does it use in population genetics?
process that saves endangered species by using population genetics
-uses migration, genetic drift, and nonrandom mating
what is migration?
movement of alleles between populations and gene pools
-creates gene flow
what is gene flow?
transfer of alleles from the gene pool of one population to a gene pool of another population
does migration increase proportions of heterozygous or homozygous alleles?
homozygous alleles
what does migration and selection prevent from occuring?
divergence of species (separation of species that creates 2 new species)
-EX: banded snakes on main island, non-banded snakes on other islands from selection = due to migration there are still banded species on the non-banded islands
what is genetic drift?
-change in allele frequencies of a population due to chance events, not natural selection
-drifts towards fixation or loss of alleles
-RANDOM subset
what size population does genetic drift have the biggest impact on?
small populations
-bigger and faster drift effects
what is the difference between selection and genetic drift?
-selection happens for a reason
-drift just happens
what can cause genetic drift in evolution when collecting samples?
sampling error (sample too small)
what is the founder effect?
genotypes (and alleles) of founding individuals will shape the evolutionary trajectory of a population
-EX: Pingelapese people, only 20 remained = achromaropsia (recessive loss of function allele), led to poor vision/blindness
what are three distinct trends for 100 generations of genetic drift?
-every population follows a unique evolutionary path
-more rapid and dramatic effect in smaller populations than large
-can produce substantial changes in allele frequencies
what happens to heterozygosity as allele frequencies in small populations drift toward fixation or loss?
heterozygosity decreases
what is an effective population size?
-number of individuals that participate in producing the next generation
-number of heterozygotes in a population
is the effective population size bigger or small than the actual population size?
smaller than the actual population size
what are the two reasons for why genetic diversity is important?
-genetic diversity is the reason for evolution
-loss of heterozygosity leads to more homozygosity
what are the three things that can result in an interaction between mutation, genetic drift, and selection?
-harmful/deleterious alleles appear and are eliminated by selection
-neutral mutations appear and are fixed or lost by chance
-advantageous alleles appear and are swept to fixation by selection
who created the neutral theory of molecular evolution?
Motoo Kimura
what did Kimura argue?
that neutral changes explain most of the DNA changes (not just majority deleterious)
what are the three major concepts on the neutral theory of molecular evolution?
-deleterious mutations are eliminated by selection and contribute very little to evolution
-neutral mutations increase and decrease in frequency as a result of genetic drift
-advantageous mutations are lost to drift or selected for fixation
what are pseudogenes?
functionless stretches of DNA that result form gene duplications
-don’t encode proteins and are thus neutral
what are synonymous (silent) mutations?
DNA sequences changes, no AA change
what are non-synonymous (replacement) mutations?
DNA sequence changes, AA change
which type of mutation (synonymous or non-symonymous) outnumber the other when sequences evolve by negative selection (getting rid of bad alleles) and drift?
synonymous mutations (no AA change) outnumber non-synonymous
which type of mutation (synonymous or non-symonymous) outnumber the other when sequences evolve by positive selection (increasing good allele) and drift?
non-synonymous mutations (AA change) outnumber synonymous
what is codon bias?
in the use of the multiple codons for one AA, one codon is favored over the others
-proves that codon selection is NONRANDOM
what is the translational efficiency hypothesis?
silent mutations can be selected against through lack of expression
-synonymous mutations aren’t selectively neutral
what is hitchhiking/selective sweep?
as a favorable mutation increase in frequency, linked genes will increase in frequency too
-in areas of reduced recombination
-positive selection
what is background selection?
negative selection against deleterious mutations in regions of reduced recombination
-removes closely linked neutral mutations and yields a reduced level of polymorphism
what is the most common example of nonrandom mating?
inbreeding
what is inbreeding?
mating among genetic relatives
what is more common in inbreeding, heterozygotes or homozygotes?
homozygotes
why can inbreeding lead to reduced fitness?
b/c it generates more homozygous for bad alleles
what does the maternal effects have on inbreeding?
can make bad effects show up later in life cycle
-masks influence of bad alleles
what is adaptation?
traits that increase fitness
-how the trait is used
-individuals with the trait contribute more genes to future generations than those lacking it
what is the oxpecker example and why is it important?
-shows that all hypotheses must be tested
-oxpecker and mammals were assumed to be mutually beneficial
-during the experiment the tick amount on cows never changes
-determined oxpeckers made more wounds, ate earwax, and didn’t remove parasites
what are the three considerations when studying adaptations?
- differences b/w populations/species are not always adaptive
- not every trait or use of a trait is an adaptation
- not every adaptation is perfect
what are experiments?
-restricts the difference b/w study groups to a single variable to test
-tests predictions made by several alternative hypotheses
-must be repeatable
what are control groups used for?
to factor out any other explanation than the single variable
-EX: jumping spider and fly = control group to see if glue is a factor, control group to see if the household fly is a factor
what are the four rules of designing an experiment?
-must define and test effective control groups
-all groups (& controls) must be tested equally
-RANDOMIZATION
-must have repeatable results for individuals
how do you minimize bias in experiments?
-through repeated tests to reduce the amount of distortion
-use a BIG sample size
-want to maximize precision of data
what is a null hypothesis?
predicts no change in relationship b/w variables
-what the researcher is trying to disprove
what is an alternative hypothesis?
predicts the changes and the relationship b/w variables
-what the researcher is proving
what do statistics do for experiements?
helps us prove if the sample is accurately represented for a population
-uses p-values to prove it isn’t due to chance
what is the difference between a controlled experiment and an observational experiment?
controlled: show cause and effect
observational: yield data for testing hypotheses
when is observation used?
when the experiment is impractical
-not as powerful though
-finds relationship b/w 2 variables
what was an important takeaway from the snake and thermoregulation at night example?
you must test all options available to the species
what is the comparative method?
-compares existing stats with historical stats
-studies evolution of form and function
-tests patterns across different species to see correlations
-MUST ACCOUNT FOR EVOLUTION OF SPECIES (phylogenetic info)
what are phylogenetically independent contrasts?
removal of divergence from common ancestor and see if contrasts are correlated
-different traits b/w nodes
what is phenotypic plasticity?
individuals with same genotype have different phenotypes if they live in different environments
-can evolve!!
can phenotypic plasticity be adaptive?
yes, can be adaptive when it allows individuals to increase fitness by changing their phenotypic expression for survival in the environment
what are the three reasons why populations can’t evolve to all selective challenges at once?
-trade offs
-constraints
-lack of genetic variation
what are trade-offs?
alternatives that are given when one is chosen over the other
-when one aspect is heavily invested, the other aspects weaken overtime
what are constraints?
restrictions/limitations on the course or outcome of adaptive evolution
-helps explain why something didn’t or doesn’t evolve
when selection at the level of organisms within populations is relatively weak, what drives evolution?
selection at the level of organelles within cells or cells within tissues
-cells, organelles, sequences, etc.
what are the 5 steps to ask a good question for research?
- study natural history (can lead to new patterns that need explanation)
2.question “obvious” (conventional) wisdom, it is often untested - question assumptions underlying a popular hypothesis, be skeptical
- draw analogies to other taxon’s or groups/species
- ask why not? (why aren’t we questioning this?, why do we believe this hypothesis?)
The spiny mouse exhibits a human-like menstruation. T/F
True
What is one strategy used by mammals to navigate underwater?
Echolocation
Do all mammal species have the same cancer mortality rate. T/F
False
Is pupil shape related to activity patterns and foraging methods in snakes?
Yes
Bipedalism evolved before encephalization in humans. T/F
True
Which hormone is responsible for the most metabolic changes in women during menopause?
Estrogen
Tiktaalik contained a humerus, radium, ulna, and digits (all of which are seen in humans and
other tetrapods). Are these structures then considered homologous to other structures we see
in today’s tetrapods?
Yes
What are the top five mammalian groups on the top of the bivariate brain-body space?
elephants, great apes, hominins, toothed whales, and delphinids
In former athletes, which joint area had the highest presence of osteophytes?
A. Hip Joint
B. Patellofemoral joint
C. Tibiofemoral joint
D. Glenohumeral joint
B. Patellofemoral joint
What human activity has forced elephants to quickly evolve to prevent diseases?
Captivity and Poaching
Was menopause found to be a recently evolved trait?
Yes
Which gene needs to be present for there to be resistance to beta-lactam antibiotics?
Mec-A Gene
The appendix is a vestigial feature. T/F
False
Which process causes organisms to look morphologically similar when they are not closely related?
Convergent evolution
Can epigenetic changes be passed from parent to offspring?
Yes
How did reptiles avoid the problems associated with invading land?
-avoided the problem of their eggs drying out on land by returning to the water to lay their eggs while other species enclose their eggs in an amniotic sac with a protective coating layer
What is one embryological trait we share with reptiles?
-a yolk in the embryonic sack with reptiles
-The yolk gene that is found in humans is inactive but proves we evolved from an egg laying animal.
How is our skin similar but different from reptiles?
-we both have layers of dead cells to protect us from drying out
-We are different with our skin because we have secretions from our skin that keeps our skin soft unlike reptiles who shed and have rough, dry skin
How are our teeth similar but different from reptiles?
-Humans and reptiles both have teeth good for biting their food into chunks
-Except reptiles have short pegged teeth that come in multiple sets throughout their life, and humans have one set of teeth such as molars that allows us to have a more precise bite.
How are all skin-based structures formed and what gene controls it?
-Skin-based structures such as hair are formed from simple skin folds and the gene called EDA
-EDA can control what is made and the quantity.
