Mutation as an Evolutionary Force

1. Mutation as an Evolutionary Force • It occurs when errors are made in duplicating alleles in producing the gametes. • It is one of the weaker evolutionary forces, because errors are relatively rare. The error rate or mutation rate, m, in copying an allele of a nuclear gene is ~ 1 x 10-6 to 1 x 10-9. • It changes allele frequencies in a population and this change in the genetic composition of a population from parents to offspring is what we mean by evolution.

2. No Mutation AA Parents produce only ‘A’ bearing gametes. Aa Parents produce ½ ‘A’ and ½ ‘a’ bearing gametes aa Parents produce only all ‘a’ bearing gametes. With Mutation AA Parents produce some ‘a’ bearing mutant gametes. Aa Parents produce ½ ‘A’ and ½ ‘a’ gametes aa Parent produce some ‘A’ bearing mutant gametes.

3. = A alleles = a alleles Parent population Reproduction With Mutation Offspring population

4. How strong is mutation as an evolutionary force? Calculate how much the frequency of an allele changes in the population as a result of mutation. μ Mechanism of Mutation a A Mutant Allele in the Gamete and then In the Offspring Allele in the Parent u a A Mutant Allele in the Gamete and then In the Offspring Allele in the Parent

5. Change in allele frequency, DPa, as a result of mutation μ Mechanism of Mutation a A u Reproduction With Mutation Offspring Frequencies: {PA’, Pa’} Parent Frequencies: {PA, Pa} How similar are PA’ and PA?

6. The change in allele frequency, DPa, caused by mutation Reproduction With Mutation Parent Frequencies: {PA, Pa} Offspring Frequencies: {PA’, Pa’} Freq of a allele in offspring after mutation Mutation rate from A to a times the Freq of A before mutation Non-Mutation rate times the Freq of a before mutation Pa’ = (1- v)Pa+ μPA ΔPa = Pa’– Pa = μ – (u + m)Pa

7. An Evolutionary Equilibrium occurs when DP = 0 • Evolution: change in allele frequency in a population from one generation to the next. DP > 0 the allele is increasing in frequency DP < 0 the allele is decreasing in frequency • No Evolution: No change in allele frequency in a population from one generation to the next. DP = 0 the allele is neither increasing nor decreasing in frequency • The Equilibrium Allele Frequency, P*, is the frequency that makes DP = 0

8. The change in allele frequency, DPa, caused by mutation ΔPa = Pa’– Pa = μ – (u + m)Pa What is the Equilibrium Allele Frequency, Pa*? SetΔPa = 0=μ – (u + m)Pa* Solve forPa*

9. The Equilibrium Allele Frequency,Pa*, that makesDPa = 0 At the Mutation Equilibrium, ΔPa = 0. 0 = μ – (u + m)Pa* P*a= μ/(u + m) The Equilibrium Allele Frequency = Rate at which A is wrongly copied as a, Relative to all errors of copying at this gene.

10. Parent Population Offspring Population YY yy yy YY yy yy YY yy yy Yy yy YY yy Yy yy YY yy Yy yy YY Yy yy Yy YY YY Yy Yy yy YY YY Yy Yy Yy YY Yy Yy yy YY Female Parents {GYY, GYy, Gyy}, {PY, Py} {GYY, GYy, Gyy}, {PY, Py} Male Parents

11. y y y y y y y y y y y y y y y y y y Y Y Y Y Y Y Y Y Y Parent Population Offspring Population YY yy yy YY yy yy YY yy yy Yy yy YY yy Yy yy YY yy Yy yy YY Yy yy Yy YY YY Yy Yy yy YY YY Yy Yy Yy YY Yy Yy yy YY Gametes: Sperm + Eggs {GYY, GYy, Gyy}, {PY, Py} {GYY, GYy, Gyy}, {PY, Py} Y Y y Y y Y y y Y Gametes are mixed by Ocean Currents For pelagic spawners and broadcast spawners

12. Pelagic eggs - eggs that float in the water column, like most deep water marine fishes and coral reef fishes. Pelagic Scatterers – spawn by scattering eggs and sperm into the water in schools near surface. For example:sardines, mackerel, tuna, whitefish. Broadcast Spawners: another name for forming zygotes by scattering eggs and sperm into the water Examples: Thunnus thynnus, atlantic blue fin tuna 10 feet long, weigh up to 1,400 pounds, lifespan longerthan 20 years. the largest bony fish in the world; theymigrate up to 5,000 miles. 0.8 to 2.6 million eggs per spawning female (roughly 100,000 eggs/kg). Eggs are ~ 1 mm in diameter and buoyant, enclosed in an oil droplet. LABRIDAE (WRASSES) All species are proto-gynous hermaphrodites: Females have the capacity to turn into males. Males are either born as males or are older sex-reversed females. Star Fishes.

13. y y y y y y y y y y y y y y y y y y Y Y Y Y Y Y Y Y Y Parent Population Offspring Population YY yy yy YY yy yy YY yy yy Yy yy YY yy Yy yy YY yy Yy yy YY Yy yy Yy YY YY Yy Yy yy YY YY Yy Yy Yy YY Yy Yy yy YY Gametes: Sperm + Eggs {GYY, GYy, Gyy}, {PY, Py} {GYY, GYy, Gyy}, {PY, Py} Y Y y Y y Y y y Y Gametes are mixed by Ocean Currents For pelagic spawners and broadcast spawners

14. Parent Population Offspring Population YY yy yy YY yy yy YY yy yy Yy yy YY yy Yy yy YY yy Yy yy YY Yy yy Yy YY YY Yy Yy yy YY YY Yy Yy Yy YY Yy Yy yy YY Female Gametes {GYY, GYy, Gyy}, {PY, Py} {GYY, GYy, Gyy}, {PY, Py} Random Mating = Random Union of Gametes Male Gametes

15. Human Blood Groups: Number of Individuals: MM MN NN Total 1787 3037 1305 6,129 Genotype Frequencies: 0.292 0.495 0.213 1.00 Number of Alleles: M N Total 6611 5647 12,258 Allele Frequencies: 0.539 0.461 1.00 Predicted Genotype (0.539)2 2(0.539)(0.461) (0.461)2 Frequencies from HWE0.291 0.497 0.212 Actual Observed 0.292 0.495 0.213

16. Human Blood Groups are in Hardy-Weinberg Equilibrium PredictedGenotype (0.539)2 2(0.539)(0.461) (0.461)2 Frequencies from HWE0.291 0.497 0.212 Actual Observed 0.292 0.495 0.213 Conclude: Humans are mating at random with respect to blood groups! Conclude: No evidence of natural selection or any other evolutionary forces acting on these alleles. Conclude: We are mating like pelagic spawners as far as this gene is concerned! Conclude: Nonrandom mating can be occurring for some traits and genes but not others in the same population.