Population Genetics Chapter 21

1. Population Genetics Chapter 21

2. Population Genetics is the study of the genes in a population.a population is all the individuals of one species in a given area.

3. Macroevolution is looking at the “Big Picture” of evolution.the creation of new species and the extinction of old ones (example lung fishes evolving into primitive amphibians)

5. Microevolution/adaptations are when the genetic code of one individual changes and enables the individual to survive better. (example natural immunity from diseases, mutation that results in camouflage)

7. Genetic codes can differ between individuals of the same species. For instance the amino acid leucine can be the result of the codons UUA, UUG, CUU, CUC, CUA, CUG.blood groups have lots of variances for blood types and blood proteinsorganisms have many different alternatives of enzymes and may behave differently.

8. If an individual has alternate codes in their DNA it is considered heterozygous. On one strand of DNA I may have UUG for leucine, but on the homologous strand I may have CUU. I am said to be heterozygous for that gene locus. This is a ‘green light’ for natural selection to occur.

9. How do we know if our genes are homo or heterozygous for certain amino acids? Run a gel electrophoresis and compare how far the proteins migrate across the gel

10. Hardy – Weinberg Equilibrium

11. In a given population of animals – random mating will not produce “crazy” genotypic ratios. They should be constant/consistent.

12. Necessary AssumptionsPopulation is very large.Random matingNo mutationNo gene input from external sources.No selection occurring

13. Hardy – Weinberg Equationp2 + 2pq + q2 = (p +q)2

14. part to memorizep2 + 2pq + q2 homo dom hetero homo recp = frequency of the dominant alleleq = frequency of the recessive allelep2 = percent of the homo dom. phenotype (outward appearance)q2 = percent of the homo rec. phenotype (outward appearance)2pq = percent of the hetero phenotype (outward appearance)

15. frequency = # of specific events # of total events Ex: # of tongue rollers in class # of students in class

16. if you are contrasting 2 events the decimal percentages should equal 1.p + q = 1So if the frequency of p = .75, then the frequency of q = .25

17. Example: You visited Gatorland Zoo in Florida and counted the number of turtles that had a notch in their upper shell (carapace).

22. Out of 100 turtles 16 % did not have a notch in their upper shell. “ “ “ “ 84 % did have the notch in their upper shell.

23. 16 % did not have a notch in their upper shell. 84 % did have the notch in their upper shell.So p2 + 2pq showed the dominant phenotype “notched shell” p2 would represent the ones that were homo dominant 2pq would represent the ones that were heterozygousboth added together equal the 84% showing the notched trait.q2 represents the recessive phenotype that do not have the notch.So q2 represents the 16 %

24. Now here comes the fun. In AP Biology you are expected to be able to calculate the frequencies of the alleles p and q. Then you will be able to pinpoint the frequencies of the homo dom and hetero phenotypes instead of grouping them together.

25. First set up three columns to show your workColumn 1 Column 2 Column q2p22pq

26. 16 % did not have a notch in their upper shell. 84 % did have the notch in their upper shell.

27. Hardy-Weinberg suggests that if random breeding is present, then in a population of turtles these frequencies should remain constant. However, if certain factors interfere, such as

28. Mutations Migration into or out of an areaGenetic drift Non-random mating Or artificial selection take place then it may upset the Hardy-Weinberg Equilibrium.

29. Mutationssomewhat rare – but have dramatic consequences in some cases. Because mutations are rare and usually affect a single individual, they don’t normally upset the Hardy-Weinberg Equilibrium.

31. Migration occurs when individuals in a population leave or enter an other area with another population.If successful mating occurs then genetic alternatives can begin to show.In some cases the individual stays behind but their gametes travel to another population such as plants releasing pollen into the wind, or clams squirting their sperm and eggs into the water column.

33. Gene Flow Tends to homologize allele frequencies.

34. Genetic Driftis when there are random fluctuations or loss of alleles in a population due to a small population becoming isolated. Example: the TV show LOST.

36. Founder principleoccurs when individuals of a species become isolated and start a new gene pool. Ex. If the characters on LOST all started breeding.

38. Bottleneck Effectis when a natural disaster like a flood, drought, earthquake, or tsunami occurs and genetic variability is restricted to the surviving individuals. Example: It is thought that the reason why we only have one species of cheetahs today is because a great catastrophe decimated the population and only a few of the same species survived (made it through the bottleneck).

40. Inbreeding occurs when blood relatives have sex. It can upset the Hardy-Weinberg Equilibrium. Inbreeding tends to increase homozygous traits, especially those that are homo recessive. Inbred animals tend to acquire homo recessive traits that can be damaging to their survival. Plants can be inbred by self-pollination.

44. Outcrossing is the opposite of inbreeding and results in more heterozygous genes/traits. Plants outcross by cross-pollination.

45. Selection is leaving behind more offspring than your competitors. Leaving behind a legacy.

46. artificial selection is when a breeder chooses which animals will be bred together.

48. natural selection is when the environment or Mother Nature allows for random mating and selects the fittest to breed.

49. Selection Pressures:Avoiding PredatorsMatching Climatic ConditionPesticide Resistance

50. Eugenics is the practice of selectively breeding humans to gain a dominant race. Society has frowned upon this practice so far.