Epistatic Interaction - 02 03-2015

This presentation describes the epistatic interaction and its importance

1. 1 EPISTATIC INTERACTIONS

2. 2 Complementary gene (9:7) Duplicate gene (15:1) Suppressor gene (13:3) Additive gene (9:6:1) Dominant epistasis (12:3:1) Recessive epistasis (9:3:4) Types

3. 3 Complementary gene (9:7)

4. Production of one phenotype requires the presence of dominant alleles of both the genes controlling the character C W ccW C ww ccww Contrasting phenotype Anyone of the two dominant gene is unable to produce the phenotype when alone They complement each other to produce concerned phenotype when they are together 4

5. 5 Reginald Punnett (left) joined William Bateson (right) in 1903

6. 6 Sweet pea ( Lathyrus odoratus )

7. 7 Duplicate gene (15:1)

8. Characters governed by duplicate gene action are determined by two completely dominant genes Duplicate gene action: The presence of a single dominant allele of any one of the two genes governing the trait produce the dominant phenotype W wwcc Contrasting phenotype 8

9. 9 Endosperm colour in maize

10. 10 Seed coat colour of oat

11. 11 Floating habit of rice

12. 12 Suppressor gene (13:3)

13. The gene don’t directly cause the expression of the characters but suppress the expression of other genes Example Leaf colour of rice: Green Purple G g I s uppress G i Ineffective 13

14. 14 Leaf colour of rice

15. Additive gene/ Polymeric genes/ Duplicate gene with cumulative effect 9:6:1 15

16. Two completely dominant genes controlling a character R W R W But both genes are present together, their phenotypic effect is enhanced as the effect of the two genes were cumulative additive R W 16 It produces identical phenotypes when they are alone

17. 17 Seed colour of wheat

18. 18 R_B_ rrbb R_bb rrB _

19. Red colour in wheat is produced by the genotype R_B_, white by the double recessive genotype, rrbb . The genotypes R_bb and rrB _ produce brown kernels. If homozygous red variety is crossed to a white variety what phenotypic results are expected in the F 1 and F 2 ? 19

20. RB Rb rB rb RB RRBB Red RRBb Red RrBB Red RrBb Red Rb RRBb Red RRbb Brown RrBb Red Rrbb Brown rB RrBB Red RrBb Red rrBB Brown rrBb Brown rb RrBb Red Rrbb Brown rrBb Brown rrbb White Punnett Square 20

21. RB Rb rB rb RB RRBB Red RRBb Red RrBB Red RrBb Red Rb RRBb Red RRbb Brown RrBb Red Rrbb Brown rB RrBB Red RrBb Red rrBB Brown rrBb Brown rb RrBb Red Rrbb Brown rrBb Brown rrbb White Punnett Square 21

22. RB Rb rB rb RB RRBB Red RRBb Red RrBB Red RrBb Red Rb RRBb Red RRbb Brown RrBb Red Rrbb Brown rB RrBB Red RrBb Red rrBB Brown rrBb Brown rb RrBb Red Rrbb Brown rrBb Brown rrbb White Punnett Square 22

23. RB Rb rB rb RB RRBB Red RRBb Red RrBB Red RrBb Red Rb RRBb Red RRbb Brown RrBb Red Rrbb Brown rB RrBB Red RrBb Red rrBB Brown rrBb Brown rb RrBb Red Rrbb Brown rrBb Brown rrbb White Punnett Square for F 2 Phenotypic ratio of F 2 generation is Red: Brown: White = 9:6:1 23

24. Dominant epistasis 12:3:1 24

25. T he two genes affecting the character W Y When both genes are present in recessive state a different phenotype is produced They produce distinct phenotype when they are alone W Y But when the genes are present together, the expression of one gene masks the expression of other Y W w y 25

26. Fruits of Cucurbita pepa will be in green, yellow and white colour . White is dominant over both yellow and green but yellow is dominant over green only. White colour is determined by the dominant gene W and no other gene for fruit colour can be expressed in its presence. Thus dominant W is epistatic to two other fruit colour . In the presence of homozygous recessive, ww another gene Y determine the yellow colour . Homozygous recessive plants for both genes, wwyy bears green fruit that the classical ratio the first two classes of a dihybrid ratio are phenotypic ally similar 26

27. 27 Fruit colour of Cucurbita pepa

28. wwyy W_ _ _ ww Y_ 28

29. When homozygous white fruit seeds are crossed with homozygous green fruit seeds, the F 1 is all white. Crossing with F 1 among themselves F 2 produced 121 white, 28 yellow and 9 green. Explain the results 29

30. WY Wy wY wy WY WWYY White WWYy White WwYY White WwYy White Wy WWYy White WWyy White WwYy White Wwyy White wY WwYY White WwYy White wwYY Yellow wwYy Yellow wy WwYy White Wwyy White wwYy Yellow wwyy Green Punnett Square 30

31. WY Wy wY wy WY WWYY White WWYy White WwYY White WwYy White Wy WWYy White WWyy White WwYy White Wwyy White wY WwYY White WwYy White wwYY Yellow wwYy Yellow wy WwYy White Wwyy White wwYy Yellow wwyy Green Punnett Square 31

32. WY Wy wY wy WY WWYY White WWYy White WwYY White WwYy White Wy WWYy White WWyy White WwYy White Wwyy White wY WwYY White WwYy White wwYY Yellow wwYy Yellow wy WwYy White Wwyy White wwYy Yellow wwyy Green Punnett Square for F 2 Phenotypic ratio of F 2 generation is White: Yellow: Green = 12:3:1 32

33. 33 Recessive epistasis 9:3:4

34. 34 In this gene interaction, the dominant allele of one gene produces a phenotypic effect The dominant allele of the other gene does not produce any phenotypic effect But when it is present with dominant allele of the first gene, it modifies the phenotypic effect produced by the first gene C A C A C A CA CA

35. 35 Coat colour of mice

36. 36 The coat colour of mice is control by two genes C and A C alone determine black colour but due to supplementary effect of A the colour is become black C_A_

37. 37 When only gene C is homozygous recessive albino mice are produce cc_ _ A alone has no effect C_ aa

38. 38 Mating between black mice of identical genotype produced offspring as follows; 14 Gray, 47 Black and 19 Albino. 1. What epistastic ratio is approximated by these offspring? 2. What are the phenotypes of the parents and offspring?

39. 39 CA Ca cA ca CA CCAA Black CCAa Black CcAA Black CcAa Black Ca CCAa Black CCaa Gary CcAa Black Ccaa Gray cA CcAA Black CcAa Black ccAA Albino ccAa Albino ca CcAa Black Ccaa Gray ccAa Albino Ccaa Albino Punnett Square for F 2 Phenotypic ratio is Black: Gray: Albino= 9: 3: 4

40. 40 Summary of epistatic interaction

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42. 42 Thank you