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Bellringer – March 13, 2014

Bellringer – March 13, 2014. Green color (G) is dominant to white color ( g ) in turtles. In a population of 200 turtles , 13% are white. A) What are the allele frequencies? B) What percentage of each genotype are in this population? C) How many turtles are heterozygous?.

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Bellringer – March 13, 2014

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  1. Bellringer – March 13, 2014 • Green color (G) is dominant to white color (g) in turtles. • In a population of 200 turtles, 13% are white. A) What are the allele frequencies? B) What percentage of each genotype are in this population? C) How many turtles are heterozygous?

  2. ANSWER KEY • G= Green g= white • White = 13% = 0.13 = gg= q2 • √0.13=√q2 A)q= 0.36 then p = 0.64 B) GG = p2= (0.64)2=0.4096= 40.96% • Gg = 2pq= 2(0.64)(0.36)=0.4608= 46.08% • gg = q2= (0.36)2= 0.1296= 12.96% C) (.4608)(200) = 92 turtles are heterozygous

  3. Practice Problem #2 • A scientist has studied the amount of PTC tasters in a population. PTC tasting is dominant. From one population, 500 individuals were sampled. The scientist found the following individuals: AA = 110, Aa = 350; aa = 40. • Calculate the genotypic and allelic frequencies for the PTC gene at this population. • Determine the genotypic and allelic frequencies expected at Hardy-Weinberg equilibrium using the homozygous recessive. Is this population in Hardy-Weinberg equilibrium? Is the population evolving?

  4. A) Actual population • AA = 110, Aa = 350; aa = 40. • AA = 110/500 = 0.22; Aa=350/500 = 0.70 ; aa= 40/500= 0.08 • A=110 + 110 + 350 = 570/1000 = 0.57; • a = 40 + 40 + 350 = 160/1000 = 0.43

  5. b) Hardy-weinberg • p=A= PTC taster q= a = PTC non-taster • 40/500= 0.08 = PTC non-taster = aa= q2 • √0.08=√q2 • q = 0.28 then p = 0.72 • RR = p2 = (0.72)2 = 0.52 = 52.00% • Rr = 2pq = 2(0.72)(0.28) = 0.40= 40.00% • rr = q2 = (0.28)2 = 0.08 = 8.00%

  6. Evolution and Zygotic Barriers (Macroevolution part 2) Ms. Kim H. Biology

  7. Why don’t similar species interbreed?? • Geographic isolation • Reproductive barriers (isolation) • Change in chromosome numbers through mutation • Adaptive radiation (example of divergent evolution) • Speciation = formation of NEW species

  8. Hello over there  A. leucurus A. harrisi Geographic Isolation

  9. Two general modes of speciation determined by the way gene flow among populations is initially interrupted:Geographic and Reproductive Isolation Speciation can occur in two ways: • Geographic:Allopatricspeciation (means “other”) • a genetic isolation WITH a geographical barrier; new group isolated from its parent population • Reproductive: Sympatric speciation (means “together”) • genetic isolation WITHOUT a geographical barrier; a reproductive barrier isolates population in SAME habitat

  10. http://bcs.whfreeman.com/thelifewire/content/chp24/2402001.htmlhttp://bcs.whfreeman.com/thelifewire/content/chp24/2402001.html Allopatric speciation Sympatric speciation

  11. http://www.pbs.org/wgbh/nova/evolution/evolution-action-salamanders.htmlhttp://www.pbs.org/wgbh/nova/evolution/evolution-action-salamanders.html

  12. Reproductive Isolation • biological factors (barriers) that stop 2 species from producing viable, fertile hybrids • Two types of barriers • Postzygotic “after the zygote” • Zygote can NOT develop • Prezygotic “before the zygote” • Sperm and egg can not fuse

  13. Pre-Zygotic Barriers

  14. Sympatric: Habitat Isolation 2 species encounter each other rarely, or not at all, because they live in different habitats, even though not isolated by physical barriers

  15. Sympatric: Temporal Isolation Late Summer Late Winter Species that breed at different times of the day, different seasons, or different years cannot mix their gametes

  16. Sympatric: Behavioral Isolation http://wps.aw.com/bc_campbell_biology_7/26/6661/1705356.cw/index.html Courtship rituals and other behaviors unique to a species are effective barriers

  17. Sympatric: Mechanical Isolation Mating organs don’t fit Morphological differences can prevent successful mating Related species may attempt to mate but CAN’T anatomically incompatible Sperm = transfer

  18. Sympatric: GameticIsolation Sperm of one species may not be able to fertilize eggs of another species Ex: specific molecules on egg coat adhere to specific molecules on sperm

  19. Post-Zygotic Barriers

  20. Reduced Hybrid Viability Salamander hybrid shows incomplete development Genes of the different parent species may interact and impair the hybrid’s development Hybrids are very weak and/or underdeveloped

  21. Reduced Hybrid Fertility Even if hybrids may live and be strong, they may be sterile

  22. Polyploidy • Polyploidy is presence of EXTRA sets of chromosomes due to accidents during cell division • ex: “nondisjunction” • It has caused the evolution of some plant species • More common in plants than in animals

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