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Chapter 7

0. Chapter 7. Human variation (and population genetics). 0. Population:. Individuals within a species that can mate with each other in nature. Biological variation (like Darwin saw) exists:. within a population. between different populations. 0.

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Chapter 7

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  1. 0 Chapter 7 Human variation (and population genetics)

  2. 0 Population: • Individuals within a species that can mate with each other in nature. Biological variation (like Darwin saw) exists: within a population. between different populations.

  3. 0 Some traits differ over a wide range with lots of variation in between… height …continuous variation We describe the population in terms of distributions

  4. Figure 7.1 Fig 7.1 0 Average continuous variation

  5. 0 Some traits differ over a wide range with lots of variation in between… height …continuous variation Other traits follow the dominant/recessive pattern we discussed earlier (blood type, Tay Sachs disease, etc.)… …discontinuous variation

  6. 0 Other traits follow the dominant/recessive pattern we discussed earlier (blood type, Tay Sachs disease, etc.)… …discontinuous variation We describe a population in terms of allelefrequencies. …….e.g., 41% of the population has type A blood

  7. 0 The study of genetic variation of populations is called…. …..population genetics The textbook has two asides here: Evolution cannot work unless there is variation within a population. We have gotten away from a morphological definition of species (like Aristotle used).

  8. 0 Traits with continuous variation often are controlled by multiple genes as well as the environment. The average for one population may be different than the average of another population. (the distribution may differ)

  9. fig 7-2

  10. 0 Traits with discontinuous variation may also vary from one population to another... “race” % with 0 blood e.g., U.S. Caucasian 47% African-American 49% U.S. Asian 40%

  11. 0 Race What does it mean?

  12. Figure 7.3c 0 • Race • Based on culture: • conquerer’s (us) vs. conquered (them) • dominate oppressed • World prior to ocean travel… • …very little mixing of cultures

  13. Figure 7.3c 0 • Race • Based on culture: • Based on morphology (appearance): • subspecies (races) • skin color, hair texture, etc.,

  14. 0 • Linnaeus: four “races” • White Europeans • Yellow Asians • Black Africans • Red Native Americans

  15. Figure 7.3c 0 • Race • Based on culture: • Based on morphology (appearance): • Based on genetics:

  16. Intelligence Is there a genetic basis for “race”? 0 What is it? How do you measure it? (see page 212)

  17. Figure 7.3c Is there a genetic basis for “race”? 0 Look at population genetics • Look at a single trait in different populations • What percentage of people havethe trait?

  18. Figure 7.3c Is there a genetic basis for “race”? 0 Blood typing maps (pg. 214) (clines) • shows only indigenous people • (original inhabitants) geographic variation

  19. Figure 7.3a 0 fig 7-3

  20. Is there a genetic basis for “race”? 0 Changes are gradual Great variability between A, B, o Doesn’t correlate with “morphological races” “no race” There are no unique genetic markers for “race” concept used to suppress others, e.g., “racism” slavery, Hitler’s Germany, anti-immigration

  21. Population genetics: 0 • Blood typing • Injured soldiers on the battle field • (mid 1800’s) A B O not compatible with each other

  22. Population genetics: 0 Blood typing Landsteiner (early 1900’s) “A” carbohydrate on red blood cells A “B” carbohydrate on red blood cells B Neither O Both (codominant) AB • A and B are antigens • (cause the immune system to attack)

  23. fig 7-4

  24. Other blood groupings: • ABO system 0 • Rh system • C, D, E: close on same chromosome • Dominant/recessive • C, D, or E Rh positive • ccddee Rh negative

  25. fig 7-5

  26. Other blood groupings: • ABO system • Rh system • MN, Duffey, others, … 0

  27. Back to population genetics: 0 • How do we keep track of the genetic make-up of a population? Hardy-Weinberg principle • IF: large population (with sexual reproduction) no selection no migration

  28. Hardy-Weinberg principle (equation) • Allele frequencies will stay the same, if… • large population (with sexual reproduction) • no selection • no migration 0 • Box 7.2 pp 222, 223 • AA Aa aa • p2 + 2pq + q2 = 1

  29. Fig 7-6

  30. German Baptist Brethren (Dunkers) 0 Fled Germany in 1719 Started colony in Pennsylvania Strict rules (no marriage outside group) • If they were genetically typical 18th century Germans . . .

  31. 0 • If they were genetically typical 18th century Germans . . . (and Hardy Weinberg applies) . . . then they should have similar genetic make-up to other populations descended from 18th century Germans.

  32. If they were genetically typical 18th century Germans . . . • (and if natural selection was working in Pennsylvania) • then they should have similar genetic make-up to their neighbors in PA.

  33. The Dunkers: 0 • no type B blood (like Native Americans) • (Germans and Pennsylvanians have 6-8%) • No Fya blood type (like Africans) • (Europeans are mostly Fya ) Other traits: more German “looking” than Native American or African

  34. fig 7-6

  35. Sequence and compare mitochondrial DNA 0 Look for similarities and differences Construct a tree to show relationships

  36. fig 7-7

  37. What is the origin of differences in these different people groups? 0 They have lived in different places (environments) and have been subjected to different selective pressures. Remember the dark / light moths?

  38. 0 What natural events help “select” humans? One of them is disease. Remember sickle cell anemia?

  39. 0 fig 7-10

  40. 0 fig 7-9

  41. Genetics of sickle-cell anemia HbA and HbS normal diseased HbA HbA normal HbA HbS sickle-cell trait (some symptoms) HbS HbS sickle-cell disease (often die young)

  42. Genetics of sickle-cell anemia 0 In the US and Caribbean, most people with sickle-cell problems were of African descent. So… check in Africa In some parts of Africa the frequency of the HBS allele is over 25% WHY?

  43. Another disease: Malaria 0

  44. Figure 7.8 0 fig 7-8

  45. fig 7-11

  46. Is there a connection? 0 HbA HbA individuals infected with Plasmodium (normal) -severe symptoms HbA HbS individuals infected with Plasmodium (carrier) -less severe symptoms (and fewer bites)

  47. Is there a connection? • Having the sickle-cell gene protects against Malaria 0

  48. Other genetic diseases also protect against Malaria: • Thalassemia • G6PD deficiency 0

  49. More Human differences: 0 Tolerance of different conditions: heat and humid african hot and dry native american cold european There were differences between “groups” pg. 236

  50. More Human differences (geographic variation): 0 Bergmann’s rule body size is larger in cold areas and smaller in warm areas Allen’s rule Protruding parts (arms, legs) are shorter and thicker in cold areas and longer and thinner in warm areas.

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