SELECTION

1. SELECTION

3. Why doesn’t selection work anymore on running speed? A) There are probably diseases involved B) Too much inbreeding producing genetic defects C) There is no more genetic variation in the stock D) Epistatic effects are now in play E) Artificial insemination programs inadvertently select for defective (weaker) sperm.

4. In order for Evolution to Occur there must be variation in the population

5. Which is NOT a cause of allele variation in a population? A) Homology B) Mutation C) Genetic recombination (cross over) D) Sexual recombination E) Migration (gene flow)

6. SO Selection & Genetic drift working on variation in the population cause EVOLUITON

7. How Effective Is Selection?Consider Artificial Selection

8. In fact, all of these plants Come from wild mustard !

9. Artificial Selection cont’. • Farm animals (e.g. chicken egg production) • 126 eggs/hen/year Today 365 eggs/hen/year

10. Artificial Selection in Dogs

11. Dogs All dog fossils from 10,000 years ago are from one species of Asian Wolf The Romans (2,000 yrs ago) had 6 breeds All other breeds have been developed in the last 400 years !!!!!

13. EVOLUTION CAN BE FAST !

14. NATURAL SELECTION • Differences in mortality & reproduction lead to differences in the proportion of alleles passing to the next generation. • Positive selection= a selective advantage for one allele and that favored allele increases in the population. • Negative selection= a selective disadvantage for a allele and that tends to disappear from the population.

15. NATURAL SELECTION IN BACTERIA • Development of antibiotic resistance in bacteria

16. e.g. NATURAL SELECTION IN BACTERIAResistance to antibiotics

17. e.g. NATURAL SELECTION IN INSECTSResistance to pesticides • Foliate insecticide

18. NATURAL SELECTION OF PLANTS TO Resistance Observed Herbicide Year Deployed

19. Please look at the video. NATURAL SELECTION IN PLANTS FOR COPPER TOLERENCE

20. WHAT PRODUCES SELECTION? • Internal Environment • e.g. genetic environment • e.g. physiological/developmental environment • External Environment • Physical Environment (water, temp., 02,) • Biological Environment • Competition • Predation • Parasitism • Food supply • Mate selection (Sexual Selection)

21. Success must be judged in 2 ways: • Absolute Terms= Will the genome work? • Relative Terms= Is the genome the best available model?

22. Small Selective Advantages • Suppose that there were a selective advantage to having a long nose and suppose there was a trend that the average nose length increased 0.001/year • How many inches will the nose grow in 100,000 years? A) 1.0 B) 10 C) 100 D) 1000 E) None of the above.

23. 100 inches! Answer Slight advantages over long time = Enormous changes!

24. SELECTION IN 2 ALLELE TRAITS • Selection against a dominant trait Genotypes: AA Aa aa Rapid elimination of the trait should occur.

25. Acondroplastic Dwarfism Caused by dominant allele D

26. Fitness & Natural Selection • How to calculate fitness Compare the success of the favored allele to that of the unfavored allele. e.g. Acondroplastic dwarfism (dominant allele) W= number of children produced by 100 dwarfs number of children produced by 100 normals W= 20/100= 0.20 = fitness coefficient for dwarfs

27. Clicker Question If W= 20/100= 0.20 is the fitness coefficient for dwarfs What is the fitness coefficient of the normal individuals? Zero 0.2 0.5 1.0 None of the above

28. Answer • Remember that the fitness of the best allele is always = 1.0 • Since the normals produce more offspring than the dwarfs, they have a W = 1.0 Dwarfism would rapidly be eliminated from the population if it were not for its high mutation rate!

29. Selection in two allele systems Cont’. • Selection against the recessive Genotypes: AA Aa aa Selection will be slow to remove the “a” allele in complete dominance because it is hidden in the heterozygous condition “Aa.” These are carriers.

30. Cystic Fibrosis • Caused by recessive trait, cc • Normal allele C, causes channels in the cell membranes (lung, gut) to allow Cl- out of cell H20 follows. If both alleles are cc, then this doesn’t happen & thick sticky mucus clogs lungs & gut & these tissues are breeding ground for bacteria

31. Cystic Fibrosis • Most common genetic disorder in Caucasians; affects 1 out of 2,500 white babies • 5% of Caucasians are carriers • CC is normal • Cc is normal, but carrier • cc has cystic fibrosis

32. Clicker Question • If two carriers have children, what are the chances that their child will have CF? • 100% • 75% • 50% • 25% • Zero %

33. Cystic Fibrosis • Cc x Cc = 25% of kids are cc & have Cystic Fib. • Why aren’t they eliminated from the pop? • Because Cc have protection against diarrhea ?

34. Selection in two allele systems Cont’. • Selection favoring heterozygotes “Aa” Can only occur if incomplete or co-dominance because the trait must be expressed. e.g. Sickle-cell anemia

35. Sickle Cell Co-dominance Normal Mild Anemia Severe Anemia HbN HbN HbN HbS HbS HbS In the USA: W = 1.0 W = 0.9 W = 0.14 In Africa: W = 0.88 W = 1.0 W = 0.14 Heterozygotes are favored in Africa because they are more resistant to malaria! The environment makes the difference on what is fit!

36. Natural Selection in Polygene TraitsDirectional Selection

37. Natural Selection in Polygene TraitsStabilizing Selection

38. Natural Selection in Polygene TraitsDisruptive Selection

39. Natural Selection in Humans • What kind of selection is this? • Directional • Stabilizing • Disruptive • None of the above • No way to know