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**Chpt. 23 The Evolution of Populations-- Population Genetics**

Natural Selection does act on individuals, in that their characteristics affect their chances of survival and their reproductive success. The evolutionary impact of natural selection is only apparent in tracking how a population of organisms change over time. Thus, populations, not individuals, evolve. Some characteristics become more common within the overall population while other characteristics decline.

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**Individuals are selected…**

Natural Selection does act on individuals, in that their characteristics affect their chances of survival and their reproductive success. The evolutionary impact of natural selection is only apparent in tracking how a population of organisms change over time. Thus, populations, not individuals, evolve. Some characteristics become more common within the overall population while other characteristics decline. Populations evolve

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**Populations evolve Individuals are selected…**

Natural Selection does act on individuals, in that their characteristics affect their chances of survival and their reproductive success. The evolutionary impact of natural selection is only apparent in tracking how a population of organisms change over time. Thus, populations, not individuals, evolve. Some characteristics become more common within the overall population while other characteristics decline. Populations evolve

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**Populations = unit of evolution **

Natural selection = mechanism of evolution Gradualism = accumulation of small changes in gene pool over LONG periods of time Natural Selection does act on individuals, in that their characteristics affect their chances of survival and their reproductive success. The evolutionary impact of natural selection is only apparent in tracking how a population of organisms change over time. Thus, populations, not individuals, evolve. Some characteristics become more common within the overall population while other characteristics decline.

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**Hardy-Weinberg Theorem**

Hardy Weinberg- nonevolving populations- Obviously, not common however, it provides baseline for determining how and why populations evolve Genetic Structure remains constant over generations Hardy Weinberg= Frequency of : p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p2+ 2pq+q2 =1 P2 frequency of AA genotype 2pq= frequency of Aa plus aA genotype q2 =frequency of the aa genotype IF THE FREQUENCIES DEVIEATE FROM EXPECTED H.W. VALUES, THEN WE KNOW THE POPULATION IS EVOLVING

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**Hardy-Weinberg Theorem**

examines the gene structure of a NON-evolving population Hardy Weinberg- nonevolving populations- Obviously, not common however, it provides baseline for determining how and why populations evolve Genetic Structure remains constant over generations Hardy Weinberg= Frequency of : p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p2+ 2pq+q2 =1 P2 frequency of AA genotype 2pq= frequency of Aa plus aA genotype q2 =frequency of the aa genotype IF THE FREQUENCIES DEVIEATE FROM EXPECTED H.W. VALUES, THEN WE KNOW THE POPULATION IS EVOLVING

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**Hardy-Weinberg Theorem examines the gene structure of a NON-evolving population.**

Obviously, this is not common, however, gives a base-line / model NULL HYPOTHESIS for determining if and why populations evolve Hardy Weinberg- nonevolving populations- Obviously, not common howecer, it provides baseline for determining how and why populations evolve Genetic Structure remains constant over generations Hardy Weinberg= Frequency of : p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p2+ 2pq+q2 =1 P2 frequency of AA genotype 2pq= frequency of Aa plus aA genotype q2 =frequency of the aa genotype IF THE FREQUENCIES DEVIEATE FROM EXPECTED H.W. VALUES, THEN WE KNOW THE POPULATION IS EVOLVING

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**This has no effect on the overall gene pool percentages.**

Hardy-Weinberg Theorem even though alleles are shuffled and recombined during meiosis and random fertilization. Hardy Weinberg- nonevolving populations- Obviously, not common howecer, it provides baseline for determining how and why populations evolve Genetic Structure remains constant over generations Hardy Weinberg= Frequency of : p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p2+ 2pq+q2 =1 P2 frequency of AA genotype 2pq= frequency of Aa plus aA genotype q2 =frequency of the aa genotype IF THE FREQUENCIES DEVIEATE FROM EXPECTED H.W. VALUES, THEN WE KNOW THE POPULATION IS EVOLVING This has no effect on the overall gene pool percentages.

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A a a a A A a A A a A a A Not SWIMMING pool…. a GENE POOL!!!

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**Hardy-Weinberg Theorem**

Gene pool frequencies (percentages) will remain unchanged if no mechanism that can cause evolution to occur acts on a population. Hardy Weinberg- nonevolving populations- Obviously, not common howecer, it provides baseline for determining how and why populations evolve Genetic Structure remains constant over generations Hardy Weinberg= Frequency of : p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p2+ 2pq+q2 =1 P2 frequency of AA genotype 2pq= frequency of Aa plus aA genotype q2 =frequency of the aa genotype IF THE FREQUENCIES DEVIEATE FROM EXPECTED H.W. VALUES, THEN WE KNOW THE POPULATION IS EVOLVING

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**Hardy-Weinberg Theorem Gene pool frequencies will remain unchanged if:**

Mutations are not occurring Hardy Weinberg- nonevolving populations- Obviously, not common howecer, it provides baseline for determining how and why populations evolve Genetic Structure remains constant over generations Hardy Weinberg= Frequency of : p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p2+ 2pq+q2 =1 P2 frequency of AA genotype 2pq= frequency of Aa plus aA genotype q2 =frequency of the aa genotype IF THE FREQUENCIES DEVIEATE FROM EXPECTED H.W. VALUES, THEN WE KNOW THE POPULATION IS EVOLVING

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**Hardy-Weinberg Theorem Gene pool frequencies will remain unchanged if:**

Natural selection is not occurring Hardy Weinberg- nonevolving populations- Obviously, not common howecer, it provides baseline for determining how and why populations evolve Genetic Structure remains constant over generations Hardy Weinberg= Frequency of : p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p2+ 2pq+q2 =1 P2 frequency of AA genotype 2pq= frequency of Aa plus aA genotype q2 =frequency of the aa genotype IF THE FREQUENCIES DEVIEATE FROM EXPECTED H.W. VALUES, THEN WE KNOW THE POPULATION IS EVOLVING

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**Hardy-Weinberg Theorem Gene pool frequencies will remain unchanged if:**

Population is LARGE Hardy Weinberg- nonevolving populations- Obviously, not common howecer, it provides baseline for determining how and why populations evolve Genetic Structure remains constant over generations Hardy Weinberg= Frequency of : p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p2+ 2pq+q2 =1 P2 frequency of AA genotype 2pq= frequency of Aa plus aA genotype q2 =frequency of the aa genotype IF THE FREQUENCIES DEVIEATE FROM EXPECTED H.W. VALUES, THEN WE KNOW THE POPULATION IS EVOLVING

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**Hardy-Weinberg Theorem Gene pool frequencies will remain unchanged if:**

EVERYONE breeds… Hardy Weinberg- nonevolving populations- Obviously, not common howecer, it provides baseline for determining how and why populations evolve Genetic Structure remains constant over generations Hardy Weinberg= Frequency of : p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p2+ 2pq+q2 =1 P2 frequency of AA genotype 2pq= frequency of Aa plus aA genotype q2 =frequency of the aa genotype IF THE FREQUENCIES DEVIEATE FROM EXPECTED H.W. VALUES, THEN WE KNOW THE POPULATION IS EVOLVING

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**Hardy-Weinberg Theorem Gene pool frequencies will remain unchanged if:**

EVERYONE randomly mates… Hardy Weinberg- nonevolving populations- Obviously, not common howecer, it provides baseline for determining how and why populations evolve Genetic Structure remains constant over generations Hardy Weinberg= Frequency of : p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p2+ 2pq+q2 =1 P2 frequency of AA genotype 2pq= frequency of Aa plus aA genotype q2 =frequency of the aa genotype IF THE FREQUENCIES DEVIEATE FROM EXPECTED H.W. VALUES, THEN WE KNOW THE POPULATION IS EVOLVING

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**Hardy-Weinberg Theorem Gene pool frequencies will remain unchanged if:**

EVERYONE produces the same number of offspring Hardy Weinberg- nonevolving populations- Obviously, not common howecer, it provides baseline for determining how and why populations evolve Genetic Structure remains constant over generations Hardy Weinberg= Frequency of : p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p2+ 2pq+q2 =1 P2 frequency of AA genotype 2pq= frequency of Aa plus aA genotype q2 =frequency of the aa genotype IF THE FREQUENCIES DEVIEATE FROM EXPECTED H.W. VALUES, THEN WE KNOW THE POPULATION IS EVOLVING

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**Hardy-Weinberg Theorem Gene pool frequencies will remain unchanged if:**

NOONE migrates in or out of the population… everyone stays Hardy Weinberg- nonevolving populations- Obviously, not common howecer, it provides baseline for determining how and why populations evolve Genetic Structure remains constant over generations Hardy Weinberg= Frequency of : p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p2+ 2pq+q2 =1 P2 frequency of AA genotype 2pq= frequency of Aa plus aA genotype q2 =frequency of the aa genotype IF THE FREQUENCIES DEVIEATE FROM EXPECTED H.W. VALUES, THEN WE KNOW THE POPULATION IS EVOLVING

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**Hardy-Weinberg Theorem**

Yeah, right.... when does THAT happen? Hardy Weinberg- nonevolving populations- Obviously, not common howecer, it provides baseline for determining how and why populations evolve Genetic Structure remains constant over generations Hardy Weinberg= Frequency of : p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p2+ 2pq+q2 =1 P2 frequency of AA genotype 2pq= frequency of Aa plus aA genotype q2 =frequency of the aa genotype IF THE FREQUENCIES DEVIEATE FROM EXPECTED H.W. VALUES, THEN WE KNOW THE POPULATION IS EVOLVING

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**5 Agents of evolutionary change:**

Mutation Gene Flow (migration) Non-random mating Genetic Drift (same # of offspring) Selection

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**Hardy-Weinberg Theorem. remember:. H. W. explains:**

Hardy-Weinberg Theorem remember: H.W. explains: the frequency of alleles remains constant in a population… unless acted upon by agents OTHER THAN sexual recombination. Hardy Weinberg- nonevolving populations- Obviously, not common howecer, it provides baseline for determining how and why populations evolve Genetic Structure remains constant over generations Hardy Weinberg= Frequency of : p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p2+ 2pq+q2 =1 P2 frequency of AA genotype 2pq= frequency of Aa plus aA genotype q2 =frequency of the aa genotype IF THE FREQUENCIES DEVIEATE FROM EXPECTED H.W. VALUES, THEN WE KNOW THE POPULATION IS EVOLVING

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**p +q = 1 p2 + 2pq + q2 = 1 Hardy-Weinberg Principle**

Mathematical statement about the relative frequency of alleles (genotypes) in a population. p +q = 1 p2 + 2pq + q2 = 1

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**Hardy-Weinberg Theorem**

Frequency of alleles remains constant in a population, unless acted upon by agents OTHER THAN sexual recombination. Inheritance does not cause changes in allele frequency. Remember: Hardy Weinberg- nonevolving populations- Obviously, not common howecer, it provides baseline for determining how and why populations evolve Genetic Structure remains constant over generations Hardy Weinberg= Frequency of : p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p2+ 2pq+q2 =1 P2 frequency of AA genotype 2pq= frequency of Aa plus aA genotype q2 =frequency of the aa genotype IF THE FREQUENCIES DEVIEATE FROM EXPECTED H.W. VALUES, THEN WE KNOW THE POPULATION IS EVOLVING

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**Hardy-Weinberg Principle**

p = frequency of dominant allele p + q = 1

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**Hardy-Weinberg Principle**

q = frequency of recessive allele p + q = 1

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**in most cases, we only know the phenotypic frequencies**

Hardy-Weinberg Principle Mathematical statement about the relative frequency of alleles (genotypes) in a population. in most cases, we only know the phenotypic frequencies

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**q2 = # of aa individuals Hardy-Weinberg Principle**

q2 = frequency of homozygote recessive individuals q2 = # of aa individuals

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**p2 = # of AA individuals Hardy-Weinberg Principle**

p2 = frequency of homozygote dominant individuals p2 = # of AA individuals

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**p = # of (AA) + 2 (# Aa) Hardy-Weinberg Principle**

p = frequency of dominant allele p = # of (AA) + 2 (# Aa)

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**q = # of (aa) + 2 (# Aa) Hardy-Weinberg Principle**

q = frequency of recessive allele q = # of (aa) + 2 (# Aa)

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**2pq = # of Aa individuals Hardy-Weinberg Principle**

2pq = frequency of heterozygote individuals 2pq = # of Aa individuals

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**Hardy-Weinberg Principle**

by comparing genotypic frequencies from one generation to the next, you can learn whether or not evolution has occurred…

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**Hardy-Weinberg Principle**

if genotypic frequencies have changed from your original count… evolution has occurred!

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**Suppose there are 1,000 individuals in a population**

Genotype Number Genotypic Frequency AA Aa aa total

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**Suppose there are 1,000 individuals in a population**

Genotypic Frequency Genotypic frequency = the proportion of a particular genotype found in a population 0.49 0.42 0.09 total 1.00 AA Aa aa

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**Suppose there are 1,000 individuals in a population**

Phenotype Number Phenotypic Frequency dominant recessive total

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**Suppose there are 1,000 individuals in a population**

Phenotypic Frequency Phenotypic frequency = the proportion of a particular phenotype found in a population 0.91 0.09 total 1.00

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**Suppose there are 1,000 individuals in a population**

Allele Number Allele Frequency A a total

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**q = Allele frequency q = frequency of recessive allele**

However, we do not know how many a’s there are just by looking at phenotype 480 Allele frequency Pssst…(There are 1,000 copies of the flower color gene in this population of 500 total flowers…) Lets first look at the frequency of alleles in a population Hardy Weinberg= Frequency: p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p(squared) + 2pq+q(squared) =1 P(squared)= frequency of AA genotype 2pq= frequency of Aa plus aA genotype Q(squared)= frequency of the aa genotype q =

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**q2 = 20/500 Genotypic frequency q2 = frequency of recessive genotype**

480 Genotypic frequency Lets first look at the frequency of alleles in a population Hardy Weinberg= Frequency: p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p(squared) + 2pq+q(squared) =1 P(squared)= frequency of AA genotype 2pq= frequency of Aa plus aA genotype Q(squared)= frequency of the aa genotype q2 = 20/500

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**q2 = .04 Genotypic frequency q2 = frequency of recessive genotype 480**

Lets first look at the frequency of alleles in a population Hardy Weinberg= Frequency: p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p(squared) + 2pq+q(squared) =1 P(squared)= frequency of AA genotype 2pq= frequency of Aa plus aA genotype Q(squared)= frequency of the aa genotype q2 = .04

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**q = .04 Allele frequency q = frequency of recessive allele 480**

Lets first look at the frequency of alleles in a population Hardy Weinberg= Frequency: p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p(squared) + 2pq+q(squared) =1 P(squared)= frequency of AA genotype 2pq= frequency of Aa plus aA genotype Q(squared)= frequency of the aa genotype q = .04

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**q = .2 Allele frequency q = frequency of recessive allele 480**

Lets first look at the frequency of alleles in a population Hardy Weinberg= Frequency: p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p(squared) + 2pq+q(squared) =1 P(squared)= frequency of AA genotype 2pq= frequency of Aa plus aA genotype Q(squared)= frequency of the aa genotype q = .2

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**q = .2 p + q = 1 p + .2 = 1 p = 1 - .2 p = .8 Allele frequency**

q = frequency of recessive allele p = frequency of dominant allele 480 q = .2 Allele frequency p + q = 1 p + .2 = 1 Lets first look at the frequency of alleles in a population Hardy Weinberg= Frequency: p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p(squared) + 2pq+q(squared) =1 P(squared)= frequency of AA genotype 2pq= frequency of Aa plus aA genotype Q(squared)= frequency of the aa genotype p = p = .8

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480 p = q = .2 Some of the pink flowers will be AA and some will be Aa Lets first look at the frequency of alleles in a population Hardy Weinberg= Frequency: p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p(squared) + 2pq+q(squared) =1 P(squared)= frequency of AA genotype 2pq= frequency of Aa plus aA genotype Q(squared)= frequency of the aa genotype p2 + 2pq + q2 = 1

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480 Some of the pink flowers will be AA and some will be Aa Lets first look at the frequency of alleles in a population Hardy Weinberg= Frequency: p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p(squared) + 2pq+q(squared) =1 P(squared)= frequency of AA genotype 2pq= frequency of Aa plus aA genotype Q(squared)= frequency of the aa genotype = 1

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**.64 X 500 individuals 320 individuals are AA**

480 How many of the pink flowers will be AA and how many will be Aa Lets first look at the frequency of alleles in a population Hardy Weinberg= Frequency: p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p(squared) + 2pq+q(squared) =1 P(squared)= frequency of AA genotype 2pq= frequency of Aa plus aA genotype Q(squared)= frequency of the aa genotype .64 X 500 individuals 320 individuals are AA

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**.32 X 500 individuals 160 individuals are Aa**

480 How many of the pink flowers will be AA and how many will be Aa Lets first look at the frequency of alleles in a population Hardy Weinberg= Frequency: p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p(squared) + 2pq+q(squared) =1 P(squared)= frequency of AA genotype 2pq= frequency of Aa plus aA genotype Q(squared)= frequency of the aa genotype .32 X 500 individuals 160 individuals are Aa

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480 320 are AA 160 are Aa 480 total Lets first look at the frequency of alleles in a population Hardy Weinberg= Frequency: p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p(squared) + 2pq+q(squared) =1 P(squared)= frequency of AA genotype 2pq= frequency of Aa plus aA genotype Q(squared)= frequency of the aa genotype

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**.8 x .8 = .64 Genetic structure of next generation**

Lets first look at the frequency of alleles in a population Hardy Weinberg= Frequency: p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p(squared) + 2pq+q(squared) =1 P(squared)= frequency of AA genotype 2pq= frequency of Aa plus aA genotype Q(squared)= frequency of the aa genotype Genetic structure of next generation

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**.2 x .2 = .04 Genetic structure of next generation**

Lets first look at the frequency of alleles in a population Hardy Weinberg= Frequency: p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p(squared) + 2pq+q(squared) =1 P(squared)= frequency of AA genotype 2pq= frequency of Aa plus aA genotype Q(squared)= frequency of the aa genotype Genetic structure of next generation

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.2 x .8 = .16 .8 x .2 = .16 .32 aA Aa Lets first look at the frequency of alleles in a population Hardy Weinberg= Frequency: p+q=1 p=1-q q=1-p Genotype frequencies also add up to 1 p(squared) + 2pq+q(squared) =1 P(squared)= frequency of AA genotype 2pq= frequency of Aa plus aA genotype Q(squared)= frequency of the aa genotype Genetic structure of next generation

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**p2 + 2pq + q2 = 1 Hardy-Weinberg Principle**

Under ideal conditions, the relative allele frequencies are the same in the offspring generation as in the parent generation. p2 + 2pq + q2 = 1

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**THEN: we know the population is evolving.**

IF: frequencies in a population deviate from Hardy-Weinberg (these are set numbers)… THEN: we know the population is evolving. Five Causes of Microevolution (generation to generation changes in a population) 1. Genetic drift (changes in a gene pool of a small population based on chance) (reduces genetic variation by fixing alleles to 1) 2. Gene flow 3. Mutation 4. Nonrandom mating 5. Natural selection

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**Weinburg, I keep telling you, I got sick of changing genes!!!**

Oh Hardy, why did you quit your job at ABERCROMBIE?

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**change over time is a result of changes in a population’s frequency of genotypes /**

genetic Five Causes of Microevolution (generation to generation changes in a population) 1. Genetic drift (changes in a gene pool of a small population based on chance) (reduces genetic variation by fixing alleles to 1) 2. Gene flow 3. Mutation 4. Nonrandom mating 5. Natural selection

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How do we measure? Five Causes of Microevolution (generation to generation changes in a population) 1. Genetic drift (changes in a gene pool of a small population based on chance) (reduces genetic variation by fixing alleles to 1) 2. Gene flow 3. Mutation 4. Nonrandom mating 5. Natural selection

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Lets work an example Five Causes of Microevolution (generation to generation changes in a population) 1. Genetic drift (changes in a gene pool of a small population based on chance) (reduces genetic variation by fixing alleles to 1) 2. Gene flow 3. Mutation 4. Nonrandom mating 5. Natural selection

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Lets Hardy!! What percentage of the human population are carriers for the allele for PKU? 1 out of 10,000 babies are born with this recessive disease Most of the time you will begin by determining the frequency of the homozygous recessive genotype Find q2 (frequency of homo recessive)

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**Lets Hardy!! Find q Find p Find pq**

What percentage of the human population are carriers for the allele for PKU? 1 out of 10,000 babies are born with this recessive disease Hint: q2 = 1 / 10,000 (frequency of aa) Find q Find p Find pq

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**AP Problems Using Hardy-Weinberg**

Solve for q2 (% of total) Solve for q (equation) Solve for p (1- q) H-W is always on the national AP Bio exam (but no calculators are allowed).

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**AP Problems Using Hardy-Weinberg**

Solve for q2 (% of total) Solve for q (equation) Solve for p (1- q) H-W is always on the national AP Bio exam (but no calculators are allowed).

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**AP Problems Using Hardy-Weinberg**

Solve for q2 (% of total) Solve for q (equation) Solve for p (1- q) H-W is always on the national AP Bio exam (but no calculators are allowed).

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**AP Problems Using Hardy-Weinberg**

Solve for q2 (% of total) Solve for q (equation) Solve for p (1- q) H-W is always on the national AP Bio exam (but no calculators are allowed)

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**AP Problems Using Hardy-Weinberg**

population: 100 cats 84 black, 16 white How many of each genotype? q2 (bb): 16/100 = .16 q (b): √.16 = 0.4 p (B): = 0.6 p2=.36 2pq=.48 q2=.16 BB Bb bb

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**AP Problems Using Hardy-Weinberg**

2pq=.48 q2=.16 Assuming H-W equilibrium BB Bb bb Null hypothesis p2=.20 2pq=.64 q2=.16 bb Bb BB Sampled data How do you explain the data?

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