Biology Unit 3 Exam 3

Explain the difference between race and ancestry from a geneticperspective. Why does this pose a challenge to race-basedmedicine?

"Race" has no genetic basis, but is instead a socialconstruct based onthe history of socioeconomic and cultural dominance."Ancestry" reflects the fact that human variationsdo have a connectionto the geographical origins of our ancestors—withenough informationabout a person's DNA, scientists can make a reasonableguess abouttheir ancestry.

"Life develops very slowly on Earth, taking billions of years or moreto develop the first single-cell life."

Abiogenesis - life takes a long time to develop, working through manyiterations of the steps outlined below.

"Extraterrestrial life found that uses very different informationchemistry."

Abiogenesis -- would suggest convergent evolution of life (similar result,but different origin)

What evidence below does NOT support the "Out-of-Africa" hypothesis?

Africa is home to the greatest diversity of large game to support human hunting.

Which is true of modern humans?

Agriculture and modern medicine have made natural selection impossible.

The scientists who developed CRISPR won the Nobel Prize only nine yearsafter their discovery. What distinguishes CRISPRfrom other forms of1genetic engineering and makes it such a promisingbiotechnologybreakthrough?

CRISPR is more precise. Genetic changes are made atspecific regions ofthe genome in situ, as opposed to being inserted atrandom via a vectorCRISPR is more versatile. It can modify, delete, orinsert whole genesCRISPR can be used to edit entire genomes and targetspecifictissues/cellsCRISPR is generally cheaper than transformation (fewsteps)

How does each characteristic in the table make a virusmore or lessdifficult to evolve resistance and/or develop a vaccine?

Characteristics that increase a viruses ability to evolve/mutate will make ithard for us to evolve resistance/develop vaccines:●DNA vs. RNA - RNA is less stable than DNA, and RNAviruses willevolve/mutate more quickly than DNA viruses.●Retroviruses mutate more quickly than any other RNAviruses b/cthey embed themselves in our genome, and this processis very errorprone.●Segmented RNA viruses evolve more quickly than single-strandedRNA viruses b/c different strains can recombine theirsegments,creating whole new strains.●Viruses with multiple hosts/animal reservoirs evolvemore quicklyb/c they have additional opportunities to evolve andre-infecthumans.

What word describes the organisms at #4, #5, and #6?

Colonies

What are two problems race-based medicine and pharmacogenomics (drugs tailored to suit one's genome)?

Confounding effects of environmentally driven health disparities. Differences between one's racial identity and ancestry.

At the level of species, humans have the biggest brain-to-bodysize of anyanimal on earth. Among individual humans, brain sizecan vary quite abit. Unlike guppies, however, relative brian sizeis only weakly (if at all)correlated with "intelligence" (arecent studyfoundit could explain, atbest, 2% of the variance in IQ test performance).Suggest at least tworeasons why brian size is not a good predictor of"intelligence" in humans.(Hint:read the followingarticlefor some ideas.)

●Brain size is not the main determinant of intelligenceinhumans--more to do with brain complexity or synapseconnectivity.●Intelligence is difficult to measure, standardizedtests don't capturethe full range of intelligence.

What advantage, with regard to movement, do animalswith bilateralsymmetry have over radial and asymmetrical animals?

●Directional movement●Head / tail layout with more advanced sensory organs

What viral genome is the least likely to mutate?

DNA

STEP 6) Why would selection have favored early "cells" that use DNAto store genetic information?

DNA is more stable / mutates at a slower rate and thus less likely to to loseadaptive mutations.

How do you reconcile the idea that "race" does nothave a biologicalfoundation with the observation that there are geneticdifferences(adaptive or otherwise) between individuals and populationsofhuman beings?

EXAMPLE: local adaptation and geographic variantsare really theexception. They are exceedingly rare and often veryspecific (e.g., a SNPthat increases high altitude tolerance). In general,they do not reflect thefull diversity of the human species. Rather, geneticistshave to go togreat lengths to find even small differences amongpopulations to doany sort of statistical analysis of genetic variationand human evolution.

Why was darker skin pigmentation initially selectedfor in earlyhominids? Explain your answer in relation to vitaminD / folate.

Early hominins lost their fur as an adaptation to running more (there isa sweat gland/hair trade off). Without fur, theirskin was exposed to thesun and UV light. Higher UV exposure selected fordarker skin b/c itprotected them from UV damage and limited the breakdownof folate,an essential nutrient.

What is gene therapy?

Editing or replacing genes to treat human disease.

What is eugenics and why did efforts implement eugenicpolicies failto achieve their goals of "perfecting the human race"?

Eugenics is the idea that undesirable traits can bebreed out ofhumans, in some cases, through forced sterilizationor genocide.Eugenics failed, from a biological standpoint, becauseeugenicistsoften targeted traits that were 1) vaguely defined,2) had complex orlittle genetic basis, and 3) were strongly influencedbyenvironmental factors.

To what taxonomic group do all organisms on this tree belong(descendants of #1)?

Eukaryotes

What evolutionary event happened at #7 (It happened at least 3times)? List several evolutionary "innovations" necessary for it tohappen.

Evolution of multicellular organisms.

Based on the figure below, how does the exposure to the microbiomeof the mother's birth canal affect an infant's risk of pathogeninfection?

Exposure to the mother's microbiome reduces the risk of pathogeninfection. Fewer pathogens are observed in infants who were exposed totheir mother's microbiome.

How does the phylogeny in Q3 differ from the one presentedin the lecturevideos (18:18 mark)?

Flatworms and roundworms are at the base of the rest of bilateral animals.In the phylogeny shown in the lecture videos, noneof the traits are lost, butadded, sequentially starting with bilateral symmetry,then open digestion,and finally a coelom.

Consider two identical twins raised in different households.Howmuch of each component of total trait variation dothey share?

Genetic variation (Vg) = 100%Environmental variation (Ve) = 0%

From his experiment, Jan van Helmont concluded that life spontaneously arises from inanimate matter. What was the main flaw in his experiment?

He didn't have a control jar.

STEP 2) If there are no enzymes or ATP to power chemical reactions,what energy source was used to form the bonds betweennucleotides? On what surface did they form?

Heat Clay surfaces b/c of electrostatic attraction

Which is thought to be the original energy source for the metabolism of the first living cells?

Heat from thermal vents

Explain why heritability can only be measured in populations,not inindividual humans (or other organisms).Hint: Startwith thedefinition of heritability.

Heritability is by definition a proportion and thusrequires a sample ofmore than one. Heritability relies on measuring variationbetweenindividuals within a population, you can't measurevariation betweenone individual.

List the three viruses above in order from theeasiesttohardestforus to evolve immunity and/or develop a permanent vaccine.

Smallpox (easiest) - A DNA-based virus with no animalreservoir. It'sevolution will be slow and so any vaccine should bestable over a lifetimeInfluenza - An RNA-based, segmented virus with ananimal reservoir. It'sevolution will be fast and so any vaccine may becomeirrelevant quickly.HIV - An RNA-based, retrovirus virus with an animalreservoir. It'sevolution will be very fast and so any vaccine maybe very hard if notimpossible to develop.

Both vitamin D and folate levels are affected by UV radiation from sunlight. Which of the following correctly explains the effects of sunlight on these vitamins?

Sunlight degrades folate but helps build vitamin D.

What is the difference between mutualism and symbiosis? Can symbioticrelationships be mutualistic?

Symbiotic relationships are any relationship between two species thatinvolves close contact for an extended period of time.Mutualistic relationships are any interaction that benefits the two speciesinteracting.Symbiotic relationships can be mutualistic, but not all symbiotic relationships are mutualisms.

What aspect of our relationship with our gut microbiome makes it specifically endosymbiotic?

The microbes live inside us

Why was DNA so crucial for the formation of complex life?

The mutation rate of DNA is 100-1000 times lower than that of RNA, allowing for the genetic code of complex structures to be maintained across generations.

Sapria​ has also lost many genes, common in other plants? Whywould natural selection favor the loss of these genes in symbioticparasites like ​Sapria​?

The parasite doesn't need the genes that other plants use forphotosynthesis or producing nutrients because the parasite drives all ofthat from its host species. All the parasite needs is to be able to get thesenutrients from its host, so natural selection will favor the acquisition of anygenes that facilitate that, even if they come from the host itself.

Due to globalization of society, humans experience the same selection pressures all over the world.

True

Scientific racism--the use of scientific methods to identify racial differences--was developed after racist systems like slavery as means to justify their continued existence.

True

The tree of life envisioned by Darwin applies well to plants and animals, but not so well to bacteria and archaea.

True

Skin color is a quantitative (polygenic) trait, meaningit isdetermined by multiple genes, each with multiple alleles(at least adozen genes have been identified to-date). Given thisinformation, isit possible for two people with medium skin tone tohave a darkskinned child?Explain your answerin terms of thelaws ofinheritance.(Hint)

Yes. Allele combinations can occur in the offspringthat result inphenotypes beyond those observed in the parents.

Important homologies in the large-scale classification of animals include...

bilateral vs. radial symmetry.

"Bt corn" is a genetically engineered corn variety that expresses a insecticidal protein from the bacteria Bacillus thuringiensis. Bt corn would be classified as...

both "transgenic" and a "GMO.".

Which phrases apply to plants, animals and fungi?

contain mitochondria

Multicellularity and endosymbiosis are both examples illustrating

cooperation based on self-benefit.

Which phrases apply to both animals and fungi but not to plants?

depend on other organisms for organic nutrients heterotrophic

Fossils of Australopithecus afarensis ("Lucy" and others) were especially significant because they...

showed that small (ape-sized) brain and fully upright (bipedal) posture occurred together in the same species.

Humans are a young species, and the populations that left Africa are even younger still. This means that individuals are genetically very similar. Any two people, sampled at random from around the world, differ at about 1 in every 1,300 nucleotides pairs. To study patterns of migration and natural selection in human populations, scientists compare SNPs, short for ___________, which are akin to alleles.

single-nucleotide polymorphisms

Which of the viruses given was able to be successfully eradicated by a vaccine because it was genetically stable with low mutation rates?

smallpox

Which statements describe the HIV virus?

targets the immune system Reverse transcriptase converts RNA virus into DNA and inserts it into host DNA, leading to permanent infection.

A person's skin color depends on

the amount of melanin in the skin; more melanin means darker color.

Homosexuality, religiosity and personality all show a high degree of heritability. This means that

the existence of a genetic basis for each trait has been inferred by studies of twins.

The "RNA World" hypothesis concerning the origin of life is supported by all of the following EXCEPT:

the fact that RNA is more stable and less prone to mutation than DNA

Selection for lighter skin in human populations migrating into northern climates was driven by...

the need for vitamin D production.

Modern archaeabacteria may tell us something about the earliest single-celled organisms because

they live in extreme habitats similar to the early Earth environment. some live in deep ocean thermal vents. they are the bacteria closest to the "root" of the tree of life.

Viruses evolved from

transposons

From shoreline to dry land

●Amphibians to birds/lizards/mammals●Shelled eggs, waterproof skin

How did bilateral symmetry play a role in the Cambrianexplosionand the diversification of the animal kingdom?

●Bilateral symmetry allowed animals to occupy new ecologicalniches.●Bilateral symmetry contributed to an increase in predator-preyinteractions that resulted in "arms races" and diversification.

From water to land

●Bony fish to tetrapods (amphibians)●Lungs, limbs

Which of these phrases apply to prokaryotes? originated ~3.8 billion years ago originated ~1.6 billion years ago have plasmids have circular chromosomes have chloroplasts have mitochondria have DNA inside a nucleus

1, 3, 4,

When researchers say they've found strong selectionon a gene orallele, they are referring to patterns in the frequency of single-nucleotide polymorphisms, or SNPs in a population. What is aSNP and what patterns indicate an allele has undergoneselection ina population?

A SNP is a single nucleotide polymorphism -- nucleotidethat variesamong individuals within a population.When a SNP is nearly universally the same in a population(e.g., afrequency near 100%), this suggests that the SNP regionand any genesassociated with it have undergone selection.Positive selection. The G-variant is near a frequencyof 100%, suggestingselection favored the allele.

You are studying native populations of fruit flies on the Hawaiian islands. In one of your populations, you observe an unusual sex ratio. Rather than the typical 1:1 ratio of females to males, this population has ratio of 3 females to every 1 male. Of the explanations below, which answer below is most likely going on this population?

A selfish genetic element located in the mitochondrial genome has spread in this population.

Based on the information above, what can you concludeabout theevolution of altitude tolerance in these separatehuman populations:did it occur multiple times independently or did evolveonce andspread across the globe?Explain your answer.

Altitude tolerance evolved multiple times independentlybecause eachpopulation has a unique SNP associated with the alleleunder selection.If the trait evolved only once, we would expect thepopulations to sharethe same SNP.

Of the following viruses, which one would most likely pose the greatest challenge to developing a stable, long-lasting vaccine?

An RNA virus that also infects rodents.

Which human traits or behaviors promote cooperation within groups and are universal across societies? All but one apply.

shame religion a sense of fairness language

Based on DNA sequence analysis, which prokaryotic ​domain​ didchloroplasts and mitochondria originate from?

Bacteria (​not​ Achaea)

Of the approaches listed below, which one is used to study the origin of life on Earth?

Biochemistry

Where would you mark the evolution of shelled (amniotic) eggs on this phylogeny of vertebrates?

D

Researchers also measuredhow many offspring each pairof fish from the "large brain"and "small brain" linesproduced the first time theyspawned. What does this graphshow?

Large-brained fish have feweroffspring than small-brained fish.

From an evolutionary perspective, why is it generally harder todevelop treatments for fungal infections vs. bacterial infections?

Fungi are eukaryotes, like ourselves, thus, any treatment that targets themhas a greater potential of harming our own cells.

Some genetically engineered organisms are classifiedas geneticallymodified organisms (GMO), but not transgenic. Whatis the distinction?

GMOs include organisms that have been geneticallymodified in any way,even if their own genes have been altered.Transgenic organisms are a type of GMO where the organism'sgenome hasbeen modified by inserting a gene from another species.

Sapria​ has acquired many genesfrom its host species. Whatmechanism, common in bacteria, is responsible for acquisition ofthese genes in ​Sapria​?

Lateral gene transfer

As vaccines offer hope a year into the pandemic,many public healthofficials are concerned about the impact ofnew variantsof SARS-CoV-2.Most of these variants have arisen in countries thatfailed to control thepandemic (B.1.1.7 in the UK, P.1 in Brazil, CAL.20Cand B.1.526 in theUnited States). Why would these variants be more likelyto arise in thesecountries?

In countries with bigger outbreaks of SARS-CoV-2,the viral population islarger, meaning there is more opportunity for newmutations to arise.

STEP 5) Why would selection have favored self-replicating moleculesenclosed in these first cell walls?

Increases the efficiency/speed of replication by keeping materials in closeproximity and high concentration.

STEP 1) Miller's experiment recreated conditions of early earth.What were the inputs to his experiment and what wasspontaneously generated?

Inputs; Water vapor Ammonia, methane,CO2 & ElectricityOutput: Nucleic acids & Amino acids

Gene therapy was used to treat a few patients with SCIDS (severe combined immunodeficiency syndrome) who have a defective adenosine deaminase (ADA) gene. The basic procedure was to introduce a normal ADA gene into the patients' white blood cells in which of the following ways?

Inserting the normal ADA gene into a retrovirus, and infecting the white blood cells with the virus.

Which of the statements about lateral gene transfer is false?

It has occurred only a few times in the history of life and contriuted to the evolution of multicellularity.

Given the information above, what characteristicsof the coronavirusmakes it more likely that when we do develop a vaccineit will last longerthan the flu vaccine (influenza), which only lastsa season?

It is single-stranded vs. being segmented like influenza.

"Lucy" is an example of an intermediate (ortransitional)fossil. Whatcharacteristic did it share with chimps and whichcharacteristics didit share with modern humans?

Key characteristics: Lucy had a small skull like achimp, but was bipedallike humans.

In your own words, explain how the evolution and diversityofhuman language supports the "Out-of-Africa" hypothesisin the sameas the distribution of human genetic diversity.

Languages are most phonemically diverse among indigenious African populations. Likewise, phonemic diversity declinesas you move awayfrom Africa. Like genetic diversity, this suggeststhat human languagesin Africa are older than languages outside of Africa.

After performing their breedingexperiment, the researchers testedwhether guppies from each treatment(large brains vs. small brains) could betrained to correctly swim towards a cardshowing either two or four dots. Theresults are below. The x-axis is thenumber of times a guppy swam towardthe correct card.What do these results demonstrate?

Large-brained fish are more intelligent (or at least, better ableto solveproblems)

Which is not a homologous trait shared by all mammals?

Live birth

What evidence did Dr. Lynn Margulis present to support her"endosymbiosis" hypothesis that mitochondria and chloroplasts were oncefree-living organisms (list three)?

Mitochondria and chloroplasts are like prokaryotic cells in that they:●Are similar in size●Have their own DNA / circle chromosomes●Reproduces by binary fission●Are phylogenetically more closely related to modern prokaryotesthan to eukaryotes.

Brains consume a lot of energy, resulting in a significant trade-off with reproduction. Given this cost, what scenario would favor the evolution of increased intelligence?

Moving into a more complex habitat.

Name at least one other benefit do we derive from our microbiomethat was mentioned in the lecture videos.

Nutrition / ability to digest food

What statement is false about human evolution?

The evolution of intelligence was necessary for humans to navigate walking on two feet.

One explanation for the explosion of animal diversity during the Cambrian is...

innovations in the animal body plan.

Explain how antibodies and antigens interact witheach other during aviral infection.

Our body produces antibodies to target antigens specificto the virusinfecting us. This allows the immune system to targetthese viruses andremove them.

Below is an image of an infant (left side) and adult(right side) skulls ofboth chimps (top;Pan) and humans (bottom;Homo).What phenomenon isillustrated by these skulls? Where else in the vertebratephylogeny did thelecture mention this same phenomenon with skulls?

Paedomorphosis

A Martian probe brings back a soil sample that contains stretches of DNA that are similar to life on Earth. This evidence would support which hypothesis?

Panspermia

What distinguishes the lineage that includes #3, #5, and #10 from theother two lineages?

Photosynthesis / autotrophic

STEP 7) Why did the evolution of photosynthesis allow early "cells"to exist in environments beyond the localized, limited energysources?

Photosynthesis allowed for cells to produce chemical energy independently, meaning they no longer needed to rely on the heat energyof their environment to drive reactions.

STEP 4) Why would selection have favored macromolecules thatcould encode and string together amino acids to make proteins?(How could proteins "improve" this molecule?)

Proteins, specifically enzymes, increase the efficiency of replication.Proteins (enzymes) are involved in DNA replication and transcription. Theribosome is made up of both rRNA and proteins.

STEP 3) What two pieces of evidence do we have from living cellstoday that RNA was the most likely first self-replicating molecule?

RNA can both store information (mRNA) and does work (rRNA, tRNA)

Which of the following observations does NOT support the claim that "races" are biologically based distinctions?

Racial difference reflect local adaptation and should be celebrated.

What component of CRISPR technology is responsible for cutting the targeted region of DNA precisely were the researcher intend's to edit the sequence?

The Cas9 enzyme

Imagine that a single-celled organism was found on a Martian rock, and that its DNA sequence placed in on the tree of life we have constructed for Earth's organisms as shown in the image.

The ancestors of the Martian organism originated on Earth.

What other societal factors discussed in the lecturevideos are responsiblefor local adaptation in human populations? Describeat least two.

The development of keeping livestock (introduced animal-borneillnesses) and the development of agriculture (higherpopulationdensity, water-borne illness associated with irrigation).

Why does the greater genetic diversity observed inAfricanpopulations support the "Out-of-Africa" hypothesis?

The greater genetic diversity in African populations indicates that theyare the oldest human populations b/c they have had more time toaccumulate mutations. Thus, humans originated in Africa.

Assume multiple pairs of identical twins were adoptedat birth bydifferent families. If you found that many of thesetwins shared thesame behavior of nail biting, even though they wereraised in different households, what would you conclude about theheritability of nail biting?

The heritability of nail biting is high, meaning thereis a strong geneticcomponent to the trait.

Why are vaccines effective at reducing the odds of getting sick from a disease?

The vaccine gives a first exposure to an antigen, causing the production of memory B and T cells. The next exposure the immune response will be quicker and greater in magnitude.

Explain in your own words, what geneticists mean whenthey saythat "race" is void of biological foundation?

There is no genetic basis to any modern or historicalracial category. Inother words, "race" does not accord with any definablegenetic group.Moreover, physical traits used to categorize race,like skin color, varycontinuously, making it impossible to draw hard andfast categories. Indeed, there is more genetic variation within any population definedby race than there is between two populations of different"races".

How does this experimentprovide insight into whyselection may not favor increasing intelligence inall species in allcontexts?

These results show a tradeoff between intelligenceand reproduction.Natural selection may not always favor the evolutionof intelligence ifthe reproductive costs are too high.

Genetic analysis of genes related to skin color reveal that SNPs associated with light skin are the same in all human populations, even in Africa. What does this tell us about the history of light skin alleles?

They existed before humans left Africa

Given your answer to the question above, what macroevolutionarypattern does this represent: homology or convergentevolution?Explain your answer.

This is an example of convergent evolution. The traithas evolvedmultiple times independently as result of naturalselection.

Why can't 'race' be biologically defined by genetic differences?

Variation between regions is significantly smaller than that within a region. race is a social, rather than biological, category.

Why are viruses considered an example of convergentevolution?

Viruses have evolved repeatedly, independently indifferent lineages of thetree of life. For example, plant viruses originatedfrom plant transposons,independent from the origin of animal viruses.

Why was lighter skin pigmentation selected for insome humanpopulations that migrated from Africa and spread acrossthe globe?Explain your answer in relation to Vitamin D / folate.

Vitamin D is produced in our skin via a reaction withsunlight. Ashumans moved into regions with lower sunlight intensity,selectionfavored lighter skin to allow for the production ofVitamin D.

How does ancestry inform us about human health andmedicaldiagnosis, but race does not?

We carry different combinations of alleles becauseof our geneticancestry. These alleles can predispose to differentmedical conditions oroutcomes. For example, individuals whose ancestrytraces back topopulations in West Africa are more likely to carryalleles responsiblefor sickle-cell anemia.Race, on the other hand, can mislead diagnostic ortreatment efforts b/crace does not always concord with ancestry (not AfricanAmerican haveWest African ancestry).

A great deal of evidence supports the hypothesis that mitochondria and chloroplasts evolved as a result of

a symbiotic relationship between small prokaryotes living within larger prokaryotes.

What are the three crucial components needed for multicellular organisms to evolve from single organisms?

ability for cells to stick together division of labor among cells selection for larger size or greater complexity

In the Miller Experiment, what organic compounds were formed and collected in the liquid water that condensed after the chamber with the electrical spark? There are two correct answers.

amino acids nucleotides

In the retrovirus HIV, the enzyme reverse transcriptase...

directs the formation of DNA based on the viral RNA molecule.

Which of the following was necessary for the evolution of multicellular organisms from single-celled protists?

division of labor among cells

The molecule that was most certainly absent from the atmosphere when life first began was

free oxygen.

The evolution of cyanobacteria changed the chemistry of the Earth forever because they were and still are what?

photosynthetic

The goal genetic engineers, broadly speaking, is to manipulate the process of __________ in an organism's cells.

gene expression

If two identical twins raised in different households exhibit the exact same behavior, this would suggest that the behavior is...

highly heritable.

Paedomorphosis...

involves the retention of juvenile traits into adulthood.

You find that increased resistance to malaria occurs in several human populations around the globe and is linked to mutations in a single gene. After a SNP analysis, however, you determine that the mutations responsible for increased malaria resistance are different in each population. This suggests that the malaria resistance...

is adaptive and evolved multiple times independently.

By comparing SNPs, scientists can identify signals of selection in particular genes, which suggests that these genes were likely favored by natural selection at some point in human history. What does a signal of selection look like?

low variation in a SNP among individuals for a given population.

How does CRISPR differ from previous techniques of gene editing?

more accurate

As a taxonomic unit, viruses are

polyphyletic

A new mutation that is harmful to the health of the individual carrying it will be quickly lost from a population via...

negative selection.