BIO 303 Exam 2

Know the conditions, fundamental conclusions and assumptions of the Hardy-Weinberg equilibrium (= theorem).

- definition: a situation in which allele and genotype frequencies in an ideal population do not change from one generation to the next Conditions: 1. No selection 2. No mutation 3. No migration 4. No genetic drift 5. Random mating Fundamental conclusions: -The allele frequency in a population will not change generation after generation -If the allele frequencies in a population are given by p and q, the genotype frequencies will be given by p2, 2pq, and q2 Assumptions: -A population is infinitely large -All of the genotypes at a locus are equally likely to survive and reproduce -No alleles enter or leave a population through migration -No mutation, because mutation would lead to new alleles, changing the frequencies of all alleles

Why do old-world primates with full-color vision have so many fossilized genes for olfaction?

- they evolved the ability to see color in order to determine which plants would provide the highest level of energy - animals that could select higher energy foods had more fitness and were more likely to survive and pass on genes - the reason for fossilized olfaction is because apes started to rely on vision instead of smell more -50% of our olfaction receptor genes are fossilized -only 5 out of 200 of olfaction genes are functional in humans

What is a selection coefficient? What do selection coefficient values tell you?

-A measure of the extent to which natural selection is acting to reduce the relative contribution of a given genotype to the next generation -Tells the strength of selection and whether or not a genotype is favored

What does fixation mean and when does it occur?

-Fixed allele-carried by all members of the population; all alternative alleles have disappeared. No genetic variation exists at a fixed locus within a population, because all individuals are genetically identical at that locus -Fixation occurs more quickly/often in small populations due to genetic drift

When dealing with conservation issues, what are the relationships between habitat fragmentation, population size, gene flow, inbreeding, homozygosity fitness, reproductive success, inbreeding depression, and extinction?

-Gene flow-the movement, or migration, of alleles from one population to another -Genetic distance-a measure of how different populations are from each other genetically. Genetic distance can inform population geneticists about levels of inbreeding within a population or about the historic relationships between populations or species

With respect to in class discussion of conservation of Missouri collared lizards and Illinois prairie chickens, what were some of the actions taken prevent extinctions? Also, what were the genetic problems faced by both populations?

-Genetic problems-small, isolated populations with little diversity -Illinois prairie chickens-was down to 2 populations; 1970s, more land was purchased- population grew, then decreased again due to lack of genetic diversity -Actions taken to prevent extinctions-artificial migration

What is heterozygote superiority?

-Heterozygote superiority occurs when the heterozygote genotype is favored above either homozygote genotype. It can allow deleterious alleles to persist in a population

Not only be able to define sampling error, but understand its interaction with genetic drift, population size.

-Only a small subset of the genetic diversity of the source population is likely to be included in the new population, and the relative frequencies of theses alleles may be very different from what they had been before -Genetic drift results from sampling error -Smaller sample = more sampling error

How does negative frequency-dependent selection work? What are examples from the book and can you recognize other

-Reproductive success is inversely proportional to the frequency of the morph Elderflower orchids (purple and yellow)-two distinct morphs to trick pollinators-more common color = lower biological fitness so they are at war trying to be the rarer morph -Pollinators learn to avoid the more common morph; the less common morph becomes more common, and then that morph is selected against because pollinators learn to avoid it -Leapfrogging" of color frequencies

What are the differences between Selection and Genetic Drift and under what condition will each be important?

-Selection occurs when genotypes differ in fitness -Outcome of selection depends on frequency of allele and effects on fitness -Population size influences power of drift and selection -Drift more powerful in small populations -Selection more powerful in large populations

What is an extinction vortex? Can you explain the example in the book?

-Small population resorts to inbreeding and genetic drift, leading to loss of genetic variability -greater prairie chicken decline

What is genetic load?

-The burden imposed by the accumulation of deleterious mutations -Associated with asexual organisms because they cannot separate deleterious mutations; offspring acquire all deleterious mutations

What impact do mutations alone have on selection?

-The only way to introduce new alleles; source of genetic diversity and source of variation for selection and drift to act -Once a new mutation arrives, drift and selection may begin to act on it. If the allele is deleterious, selection will act to reduce its frequency. New mutations at that locus will keep emerging, lifting up the allele's frequency. The production of new alleles and negative selection will act like opposing teams in a tug of war

Understand when homozygotes are favored by selection and when heterozygotes are favored.

-balancing selection favors heterozygotes -negative frequency dependent selection -example: sickle cell anemia -However, in areas that don't have the presence of malaria the homozygous (AA) allele is favored

garter snakes and rough skinned newt

-high levels of TTX evolved in newts and caused the garter snakes to alter the shape of the receptor that TTX binds to -however, high resistance is costly -resistant snakes are slower -toxic newts spend lots of energy producing TTX

What are the important nuances of genetic drift with respect to evolution?

-is a non-selection, random form of evolution -does not lead to adaptation -small populations are more greatly influenced by genetic drift -results in a loss of heterozygosity

What is genome duplication and what are some examples in nature?

-is a product of nondisjunction during meiosis which results in additional copies of the entire genome being passed on - example: there is compelling evidence that angiosperms underwent two whole-genome duplication events early during their evolutionary history -example: racerunners and whiptails -females whiptails are polyploidy and able to reproduce without males (parthenogenic)

What is an evolutionary arms race? Why is it a race with no end?

-occurs when species interact antagonistically in a way that results in each species exerting reciprocal directional selection on the other -as one species evolves to overcome the weapons the weapons of the other it, in turn, selects for new weaponry ion its oppponents

What is coefficient of inbreeding (F)?

-refers to the probability that the two alleles at any locus in an individual will be identical because of common descent -F can be estimated for an individual, F(pedigree), by measuring the reduction in heterozygosity across loci within the genome of that individual attributable to inbreeding, or it can be estimated for a population by measuring the reduction in heterozygosity at one or a few loci sampled for many different individuals within the population

What is the concept of "use it or lose it"?

-the idea that if an organism does not use a specific gene, organ, etc. then the functionality of that gene/organ/etc. will decrease over time

soapberry bug

-the soapberry bug drills into the center of fruits for nutrients -when the invasive plant (balloon vine fruits) introduced the average length of the soapberry beak has increased over time to fit the plant -caused an increase in fitness because they are able to feed on the seeds 2 times faster -bugs in the north have had a lot more time to adapt to the balloon vine & have beak length perfectly matching the diameter of the fruit

parasitic wasps and aphids

-the success rate of wasps parasitizing the aphid (cloned) was different showing that some type of heritable variation -same was true for the ability of an aphid to suffocate the wasp larva

What are evolutionary trade-offs and what are some examples?

-traits are often linked in ways that prevent simultaneous optimization of all of them. -resulting 'evolutionary tradeoffs' reflect necessary compromises among the functions of multiple traits -Such compromises are particularly clear when energy must be allocated among competing metabolic functions. - examples: -big brain and small gut or small brain and big gut

viruses affect on bacteria

-viruses act as agents of selection and bacteria defend themselves & become agents of selection as well -bacteria can produce different receptors so the virus cannot attack or have enzymes that recognize and destroy virus

Know what happens when each of the assumptions is violated

-when alleles are not in equilibrium, evolution is occurring -The offspring genotype frequencies will differ from the equilibrium predictions of the Hardy-Weinberg theorem. Because they alter allele frequencies from one generation to the next, drift, selection, migration, and mutation are all possible mechanisms of evolution

What are the 3 factors that effect the geographic mosaic theory of coevolution

1. geographic variation in the type of selecting in interacting species 2. the geographic variation in the strength of reciprocal selection resulting from these interactions 3. the geographic variation in the distribution of traits that evolve in response to this selection

What type of relationships generally generate negative frequency-dependent selection

Antagonist

What is genetic drift?

Change in frequencies of allele copies in populations resulting from sampling error in drawing gametes from gene pool to make zygotes and from chance variation in the survival and/or reproductive success of individuals; resulting in non-adaptive evolution

Are mutations usually deleterious, beneficial, or neutral?

Neutral

Under what conditions does inbreeding have a minimal impact?

On its own, inbreeding does not change the frequency of alleles in a population. It simply rearranges alleles such that homozygotes for rare recessive alleles become more common. This means that inbreeding on its own is not a mechanism of evolution, but it can create the conditions for evolution to take place. When deleterious rare alleles are combined in homozygotes, they can cause genetic disorders that lower fitness. Selection can then reduce the frequency of these rare alleles, reducing the genetic variation in the population

What are the problems and benefits of inbreeding?

Rare deleterious alleles can become unmasked in homozygotes because parents in these populations tend to be closely related and are thus much more likely to share rare alleles than are two people picked at random from a large populations. The more closely related the parents are, the greater the odds that their children will be homozygous for recessive alleles, including alleles that are deleterious -high rates of infant mortality

What is the relationship between population size and mutation impact?

Smaller population size, larger mutation impact

What is its relationship with sampling error, genetic drift, population size, and conservation issues?

This effect can cause the new population to differ considerably from the source population

What are somatic mutations?

affect cells in the body of the organism; not heritable

What are germ-line mutations?

affect gametes and mutations are heritable; relevant to evolution

What are two types of genetic drift?

bottleneck and founder effect

What are point mutations?

change of only one nucleotide base in the DNA or RNA molecule

What are Inversions and what are some examples?

chromosome rearrangement in which a segment of a chromosome is reversed end to end -example: recurrent inversions giving rise to disease causes hemophilia A, an X-linked disorder (medical condition in which the ability of the blood to clot is severely reduced, causing the sufferer to bleed severely from even a slight injury) and Hunter syndrome

What is Gene Duplication and what are some significant examples that pertain to humans?

happens when an extra copy of a gene is made in an organism's genome. In some cases, the duplication leads to the gain of a new function, but in other cases, protein function is lost -examples: - ancestral opsin gene that allowed apes to develop color vision was a result of gene duplication of the green and red opsin gene - bacterial photoreceptor = single celled protist = invertebrate eye = vertebrate eye

What is inbreeding depression?

is a reduction in the average fitness of inbred individuals relative to that of outbred individuals. It arises because rare, recessive alleles become expressed in homozygous state where they can detrimentally affect the performance of inidviduals

coevolution

is the reciprocal evolutionary change between interacting species, driven by natural selection

geographic mosaic theory of evolution

proposes that the geographic structure of the populations is central to the dynamics of coevolution, the direction and intensity of coevolution varies from population to population, and coevolved genes from these populations mix together as a result of gene flow

What is negative frequency-dependent selection?

takes place when rare genotypes have higher fitness than common genotypes. This process can maintain variation within populations

reciprocal selection

the selection that occurs in two species due to their interactions with one another, is the critical prerequisite of coevolution

What are indels?

the string of bases that get inserted or deleted in a mutation

What are Insertions and what are some examples?

when a small string of nucleotide bases (called indels) are inserted into a genome -examples: Huntington's disease and the fragile X syndrome are examples of insertion mutation wherein trinucleotide repeats are inserted into the DNA sequence leading to these diseases.

What are deletions and what are some examples?

when an indel(s) is deleted from a genome -example: 22q11.2 deletion syndrome is caused by the deletion of some bases of chromosome 22. This disease is characterized by cleft palate, heart defects, autoimmune disorders etc.

What is founder effect?

" A type of genetic drift. It describes the loss of allelic variation that accompanies founding of a new population from a very small number of individuals (a small sample of a much larger source population).