agents of micro evolution

8/14/2019 Agents of Micro Evolution

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Agents ofAgents of

MicroevolutionMicroevolution


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MutationMutation


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hemoglobintetramer

sickle cell Hb(forms long

tubular rods)


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MutationMutation(ex.,CFTR gene)(ex.,CFTR gene)

Found on chromosome 7Found on chromosome 7

Codes for a protein that is 1,480 amino acidsCodes for a protein that is 1,480 amino acids

longlong

Deletion of 3 nucleotides at positions 507-508Deletion of 3 nucleotides at positions 507-508in the CFTR proteinin the CFTR protein

Results to the genetic disorder cysticResults to the genetic disorder cystic

fibrosisfibrosis

Common among Caucasian-Americans, one inCommon among Caucasian-Americans, one inevery 2,000 birthsevery 2,000 births


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G

T VALINE 510

T

G

G GLYCINE 509

T

TT PHENYLALANINE 508 --> NO 508

T

A

T ISOLEUCINE 507

C --> ISOLEUCINE

507

A

T ISOLEUCINE 506

C

CFTRCFTR gene mutationgene mutation
http://porpax.bio.miami.edu/~cmallery/150/evol/HW.htm


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Protein coded for byProtein coded for by CFTRCFTR genegene


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MigrationMigration


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Genetic Drift:Genetic Drift: BottleneckBottleneckeffecteffect

Genetically diverse

Geneticdiversity lost


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Genetic driftGenetic drift:: BottleneckBottleneckeffecteffect

Caused by intense competition, adverseCaused by intense competition, adverse

environmental conditions, or parasitismenvironmental conditions, or parasitism

Increases the rate of random genetic driftIncreases the rate of random genetic drift

Inbreeding is also increased due to reducedInbreeding is also increased due to reducedgenetic poolgenetic pool

Reduces resistance to parasites andReduces resistance to parasites and

diseases, & the ability to respond todiseases, & the ability to respond toenvironmental changesenvironmental changes

Genetic variation is reducedGenetic variation is reduced


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Population bottleneckPopulation bottleneck

By 1910, it isBy 1910, it isestimated thatestimated that

there were lessthere were less

than 100than 100

elephant seals, allelephant seals, allfound onfound on

Guadalupe island,Guadalupe island,

in Mexico.in Mexico.

PresentPresent

population ispopulation is

estimated to beestimated to be

more thanmore than150 000.150 000.

Northernelephant seal


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Population bottleneckPopulation bottleneck

Exhibits almostExhibits almost

no allelicno allelic

variationvariation

Assumed to haveAssumed to havesurvived a great,survived a great,

persistentpersistent

populationpopulation

bottleneck somebottleneck some10,000 years ago10,000 years ago

Cheetah


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Genetic driftGenetic drift:: Founder effectFounder effect

exemplified by the Dunkers ofexemplified by the Dunkers of

PennsylvaniaPennsylvania

Result of blood type survey: Nearly 60Result of blood type survey: Nearly 60

% of the Dunkers had blood type A;% of the Dunkers had blood type A;

the West German population was 45 %the West German population was 45 %

A and the US neighbor population wasA and the US neighbor population was

only 40 %.only 40 %.Little dispersal; new alleleLittle dispersal; new allele

predominatespredominates


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Nonrandom matingNonrandom mating

InbreedingInbreeding

lessenslessens

heterozygosityheterozygosity

Increases theIncreases thechance ofchance of

producingproducing

offsprings withoffsprings with

defectivedefectivegenesgenes


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Ellis van Creveld syndrome


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Royal family afflicted withRoyal family afflicted with

hemophiliahemophilia


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Selection:Selection: Natural selectionNatural selection

Stabilizing selectionStabilizing selection limits extremeslimits extremes

of populationof population

Examples: human birth weight,Examples: human birth weight,

gallmaking flygallmaking fly EurostaEurosta

Operates in stable habitatsOperates in stable habitats


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StabilizingStabilizing

selectionselection

Eurosta solidaginis(fly), laying its eggson goldenrod(Solidago altissima)stem

Eurytomagigantea

(wasp)

Downy woodpecker


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DirectionalDirectional

selection-selection- a singlea single

allele is favored;allele is favored;

allele frequencyallele frequencycontinuously shiftscontinuously shifts

to one directionto one direction

The population isThe population is

faced with a newfaced with a newenvironmentalenvironmental

conditioncondition


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Disruptive selection- intermediateforms are selected against


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agents of micro evolution

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