Chapter 23 Sections Pgs Objective: I can determine if a population is evolving by doing Hardy-Weinberg calculations.

Darwin’s Logical Flaw (Criticisms at his time)  Darwin came up with evolution without knowing any genetics Knew heredity, but not how inherited: did not know system of genes and alleles (who did?)  Mendel came up with genetics (genes/alleles) a few years after Origin of Species  Combine their ideas as well as other biology ideas = Modern Theory of Evolution a.k.a. Modern Synthesis

Modern Synthesis – Evolution Today  Natural Selection can only act on variation already present…but where does variation come from?Specify: genetic variation  Two General Categories Mutation: creation of new alleles/genes ○ Specifically…outside mutagens / internal mistakes in replication  change sequence, chromosomal mut. Recombination: mix up and new combinations of alleles/genes ○ Specifically, sexual reproduction which incorporates crossing over, independent assortment, and random fertilization

What is genetic variation?  Variation that is inheritable Environment can cause variation that is not inheritable (but sometimes can…)  Misconception: Evolution is random Evolution is NOT random…it’s selective… So…what IS random?  Mutation/Genetic variation is random, but must occur in germ cell in order to be inherited

Measuring Genetic Variation  Genetic Variation between Populations Geographic variation = difference in genetic composition of separate populations (could be same species…) Cline = graded change in character along geographic axis (how many genes/traits there are)

Measuring Genetic Variation  Genetic Variation within a Population Average Heterozygosity = percentage of loci that are heterozygous ○ More heterozygotes = more variation  Can also measure nucleotide variability…  Note: average heterozygosity tends to be greater than nucleotide variability Gene is made of thousands of bases Genome is millions of bases long ○ A difference in 1 base is sufficient to change alleles  make it heterozygous (but may not cause this change)

Defining Evolution More Specifically  Most people think of Evolution as…  Macroevolution Change over long periods of time New species evolving from old species  Microevolution: change in genetic makeup Changes that occur within 1 species Results in adaptations (more “fit” traits)  Microevolution leads to Macroevolution Small changes accumulate to large  Examining microevolution leads to… What is connection?

Population Genetics  Gene Pool: collection of genes for a given population (in a given area) Example: there exists a gene for blonde hair in humans, but for the population of humans in Africa/Asia, that gene is (most likely) absent from their gene pool  Population: a localized group of individuals in a given area capable of interbreeding Considering the following: Will gene pool EVER change? Will there be a blond allele? How can gene pool change? Possible mutation, possible migrate in, etc. If 2% of people had blonde hair, will it ever increase? What might cause that?

Allele Frequency  Evolution can be quantifiably measured (IS it occurring? how much is it occurring?) by looking at changes in allele frequency (always deicmal) : relative amount of a given allele in a population Example: in a population of 10 rats, the frequency of the albino allele is 0.1 (10%) 10 rats have 20 alleles (for this characteristic) 2 of those 20 alleles are the albino allele Will the frequency of albino gene REMAIN at 0.1? Yes, but only if not evolving…which means… Yes, if remain at Hardy-Weinberg equilibrium

Hardy-Weinberg Equilibrium  A state where population is NOT (micro)evolving Thus, can be used to determine if evolution is occurring  Two algebraic formulas that equates allele frequencies with genotype frequencies 5 conditions must be met: ○ Large population ○ No gene flow (no migration) ○ No mutations ○ Random mating ○ No Natural Selection In other words, no evolution is occurring

Hardy-Weinberg: The Formula p = the dominant allele frequency (not always bigger) q = the recessive allele frequency (not always smaller) 1 = total (for left box – total alleles) p + q = 1 p 2 = the homozygous dominant genotype frequency 2pq = the heterozygous genotype frequency q 2 = the homozygous recessive genotype frequency 1 = total (for right box – total genotypes/individuals) p 2 + 2pq + q 2 = 1 *Remember: each genotype/individual gets 2 alleles

Genotype and Allele Frequencies  In a given population (gene pool)… examine 1 characteristic with 2 alleles  Example: 100 rats living in a house Fur color: Black (B) vs. white (b)  25 white, 75 black (50 homo dom, 50 hetero) will have 100 b’s and 100 B’s in gene pool  Note: 100 total rats  200 total alleles/genes  Frequency of b allele = 100/200 = 50% = 0.5 = q  Frequency of B allele = 100/200 = 50% = 0.5 = p  Is the population evolving? NO H-W Equil.) Genotype Frequencies Homo Dom: = 0.25 = p 2 Heterozyg: = 0.50 =2pq Homo Rec: = 0.25 = q 2

Genotype and Allele Frequencies  In a given population (gene pool)… examine 1 characteristic with 2 alleles  Example: 100 rats living in a house Fur color: Black (B) vs. white (b)  10 white, 90 black (50 homo dom, 40 hetero) will have 60 b’s and 140 B’s in gene pool  Note: 100 total rats  200 total alleles/genes  Frequency of b allele = 60/200 = 30% = 0.3 = q  Frequency of B allele = 140/200 = 70% = 0.7 = p  Is the population evolving? Yes ( H-W Equil. ) Genotype Frequencies Homo Dom: = 0.50 = p 2 Heterozyg: = 0.40 =2pq Homo Rec: = 0.10 = q 2

p 2 = pq = 0.48 q 2 = 0.16 p = 0.6 = √0.36 q = 0.4 = √0.16 Since Hardy-Weinberg is at equilibrium (equation works), then the population is NOT evolving… Where did H-W come from?

 Recombination does NOT change allele frequencies (recombination includes…) Crossing Over, Independent Assortment, Random Fertilization Recombination & Allele Frequencies 1000 red1000 white 2000 C R 2000 C W 50% C R 50% C W p = 0.5q = 0.5 *Looking at allele frequencies is like looking at frequencies of gametes! 100% ♂♀ spermegg

 Recombination does NOT change allele frequencies (recombination includes…) Crossing Over, Independent Assortment, Random Fertilization Recombination & Allele Frequencies 1000 white 2000 C R 2000 C W 50% C R 50% C W q = % C R 50% C W p = 0.5q = red p = 0.5 Incomplete Dominance! This is… 1000 pink 1000 C R 1000 C W some ♂ some ♀  25% CRCR CWCW CRCR CRCRCRCR CRCWCRCW CWCW CRCWCRCW CWCWCWCW

Recombination & Allele Frequencies 50% C R 50% C W p = 0.5q = % C R 50% C W p = 0.5q = Red 200 Pink 100 White 200 C R 100 C R 100 C W 200 C W 300 C R 300 C W

Recombination & Allele Frequencies 50% C R 50% C W p = 0.5q = % C R 50% C W p = 0.5q = 0.5 CRCR CRCR CRCR CRCRCRCR CRCRCRCR CRCR CRCRCRCR CRCRCRCR CRCR CWCW CRCR CRCRCRCR CRCWCRCW CRCR CRCRCRCR CRCWCRCW CRCR CWCW CWCW CRCWCRCW CWCWCWCW CWCW CRCWCRCW CWCWCWCW CWCW CWCW CWCW CWCWCWCW CWCWCWCW CWCW CWCWCWCW CWCWCWCW CRCR CRCR CWCW CRCWCRCW CRCWCRCW CWCW CRCWCRCW CRCWCRCW 25%

What’s the %&$ point!?  Allele frequencies do not change, even with recombination Mendelian inheritance preserves genetic variation (however it is varied) from one generation to next ○ Even if variation not evenly divided 50-50…

Allele frequencies WILL change when…  Population is evolving… There are 4 agents of evolution… ○ Will discuss specific causes of (micro)evolution later…  When evolution occurs, cannot use Hardy- Weinberg to calculate allele frequencies, because they are changed Have to calculate “manually”

Reviewing Hardy-Weinberg (if you get it, then start working)  Use Hardy-Weinberg to deduce allele + genotype frequencies (# of heterozygotes) If examine frequencies from one generation to the next… ○ Allows us to determine if population is evolving H-W will fail if evolving  Cannot simply look at change to phenotype frequencies to say if evolving

Example BBBBBbBbBbBBBBbbbbBb 10 individuals – 20 alleles Phenotype: 8 black, 2 white Alleles: 12 B (p = 0.6) and 8 b (q = 0.4) BBBBBbBbBbBbBbBbBbBb 10 individuals – 20 alleles Phenotype: 10 black, 0 white Alleles: 12 B (p = 0.6) and 8 b (q = 0.4) NOT EVOLVING Reminder: frequency = part divided by whole as a decimal (can view as percentage) *Note: should count genotypes, too… Can predict ALL frequencies if population grows to 1,000,000

Example BBBBBbBbBbBBBBbbbbBb 10 individuals – 20 alleles Phenotype: 8 black, 2 white Alleles: 12 B (p = 0.6) and 8 b (q = 0.4) BbBbBbBbBbBbbbbbBbBb 10 individuals – 20 alleles Phenotype: 8 black, 2 white Alleles: 8 B (p = 0.4) and 12 b (q = 0.6) EVOLVING *Note: should count genotypes, too… Reminder: frequency = part divided by whole as a decimal (can view as percentage) Cannot predict ALL frequencies via H-W (must “manually” count)

If in H-W equilibrium, can solve… Blue-footed boobies could have no webbing (W) or webbing (w) In a population Eq.) of 500 boobies, 20 have webbing # of no webbing = # of Homozygous Dominant no Webbing = # of Heterozygous no Webbing = # of webbing = Total # of Alleles = Total # of B = Total # of b =  p =  q = p 2 = q 2 = 2pq = Theoretical #’s IF in H-W Eq = 0.04 q2q2 q = √0.04 q =0.2 W w p + q = 1 p =0.8 p 2 =0.642pq =0.32 p 2 + 2pq + q 2 = 1 (0.64)(500) 320 (0.32)(500) 160

Classroom Example with Cats # of Black Cats = # of White Cats = # of Homozygous Dominant Black Cats = # of Heterozygous Black Cats = Total # of Cats = Total # of Alleles = Total # of B = Total # of b =  p =  q = p 2 = q 2 = 2pq = Theoretical #’s IF in H-W Eq.

Classroom Example with Cats # of Black Cats = # of White Cats = # of Homozygous Dominant Black Cats = # of Heterozygous Black Cats = Total # of Cats = Total # of Alleles = Total # of B = Total # of b =  p =  q = p 2 = q 2 = 2pq = Theoretical #’s IF in H-W Eq.