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Interaction of genes
- 2. KUVEMPU UNIVERSITY Department of Applied Botany. Jnana Sahyadri, Shankaraghatta-577451 Seminar on, Interaction of Genes. By, Shilpa A. R. M.Sc., Fourth semester. Under the guidance of, Dr. Sathisha A. M. The Lecturer, Department of Applied Botany. 2018
- 3. Content. • Introduction. • Non Allelic gene interaction • Allelic gene interaction • Conclusion. • Reference.
- 4. INTRODUCTION The expression of single character by the interaction of more than one pair of genes is called Interaction of genes. Bateson and Punnet proposed factor hypothesis to explain Interaction of genes. The genic interaction is of two types, namely 1. Non-allelic gene interaction. 2. Allelic gene interaction.
- 5. Non-allelic gene interaction The interaction of gene occurs between genes located in different locus of the same chromosomes or different chromosomes is known as Non-allelic gene interaction. Some of the important forms of Non-allelic gene interactions are as follows:- 1. Complementary genes 2. Supplementary genes 3. Duplicate genes 4. Epistasis 5. Lethal genes
- 6. Complementary gene interaction It is a kind of two different dominant gene interaction in which, when both dominant gene present alone both of them fails to express their character but they complement together they produce their effect. Such a type of gene interaction results in 9:7 phenotypic ratio in F2 generation. Example: Flower colour in Sweet pea (Lathyrus odoratus L.)
- 7. White X White - Parent phenotype CCee X ccEE - Parent genotype Ce X cE - Parent gametes CcEe - F1 hybrid; all are Red flower plants F1 plants are subjected to self fertilization Red X Red - F1 Phenotype CcEe X CcEe - F1 Genotype CE Ce cE ce X CE Ce cE ce - F1 Gametes Red: White - Phenotypic ratio 9:7 Gametes CE Ce cE ce CE CCEE Red CCEe Red CcEE Red CcEe Red Ce CCEe Red Ccee White CcEe Red Ccee White cE CcEE Red CcEe Red ccEE White ccEe White ce CcEe Red Ccee White ccEe White ccee White
- 8. Supplementary gene interaction It is a kind of two different dominant gene interaction, in which one dominant gene capable to express its character when it is present alone or with the second dominant gene, where as the second dominant gene fails to express its character when it is present alone but when it is supplemented with first dominant gene it express it character. This type if interaction results in 9:3:4 phenotypic ratio in the F2 generation. Example: Flower colour in Snap dragon (Antirrhinum majus L.)
- 9. Ivory X White - Parent phenotype IIww X WWii - Parent genotype Iw X Wi - Parent gametes IiWw - F1 hybrid; all are Magenta flower plants F1 plants are subjected to self fertilization Magenta X Magenta - F1 Phenotype IiWw X IiWw - F1 Genotype IW Iw iW iw X IW Iw iW iw - F1 Gametes Magenta : Ivory : White - Phenotypic ratio 9 : 3 : 4 Gametes IW Iw iW iw IW IIWW Magenta IIWw Magenta IiWW Magenta IiWw Magenta Iw IIWw Magenta Iiww Ivory IiWw Magenta Iiww Ivory iW IiWW Magenta IiWw Magenta iiWW White iiWw White iw IiWw Magenta Iiww Ivory iiWw White iiww White
- 10. Duplicate gene interaction When a single character is controlled by two or more pair of non-allelic genes independently or when a dominant allele at either of two loci can mask the expression of recessive alleles at the two loci, it is known as duplicate gene interaction. Example: Awn character in rice. (Oryza sativa L.)
- 11. Awned Rice X Awnless Rice - Parent phenotype AAbb X aaBB - Parent genotype Ab X aB - Parent gametes AaBb - F1 hybrid; all are Awned rice variety F1 plants are subjected to self fertilization Awned rice X Awned rice - F1 Phenotype AaBb X AaBb - F1 Genotype AB Ab aB ab X AB Ab aB ab - F1 Gametes Awned Rice: Awnless Rice - Phenotypic ratio 15:1 Gametes AB Ab aB ab AB AABB Awned Rice AABb Awned Rice AaBB Awned Rice AaBb Awned Rice Ab AABb Awned Rice Aabb Awned Rice AaBb Awned Rice Aabb Awned Rice aB AaBB Awned Rice AaBb Awned Rice aaBB Awned Rice aaBb Awned Rice ab AaBb Awned Rice aAbb Awned Rice aaBb Awned Rice aabb Awnless Rice
- 12. Epistasis or Epistatic gene interaction It is a kind of two different dominant gene interaction, in which both dominant gene present alone they express their own character, when they present together one dominant gene prevent the expression of another dominant gene. The dominant gene which is going to prevent the expression of the character of another dominant gene is called Epistatic gene and dominant gene whose expression of character is prevented is called Hypostatic gene. This kind of gene interaction results in 12:3:1 phenotypic ratio in the F2 generation. Example: Fruit colour in Cucurbita.
- 13. White X Yellow - Parent phenotype WWyy X wwYY - Parent genotype Wy X wY - Parent gametes WwYy - F1 hybrid; all are White fruited variety F1 plants are subjected to self fertilization White X White - F1 Phenotype WwYy X WwYy - F1 Genotype WY Wy wY wy X WY Wy wY wy - F1 Gametes White: Yellow: Green - Phenotypic ratio 12 : 3 : 1 Gametes 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
- 14. Lethal gene A lethal gene kill its possessor. Thus the victim of lethal genes do not live to reproduce. Example: lethal gene in maize. (Zea mays L.) Albinism in maize is good example for lethal gene in plants. Maize produce albino (white) individuals which lack chlorophyll. These individuals die in the seedling stage as soon as the reserve food of the seed is exhausted.
- 15. Green plants are subjected to self fertilization, Green X Green - F1 Phenotype Ww X Ww - F1 Genotype W w X W w - F1 Gametes Green: White –Phenotypic ratio 3 : 1 Homo.green : Hetero.green : Homo.white -Genotypic ratio 1 : 2 : 1 Here, the recessive gene ‘w’ is lethal in homozygous condition. Then, the 1:2:1 ratio is modified to 1:2 due to lethality. Gametes W w W WW Green Ww Green w Ww Green Ww White
- 16. Allelic gene interaction The interaction of gene between the two alleles of a single locus is known as allelic gene interaction Some of the important forms of Allelic gene interaction are as follows :- 1. Complete dominance 2. Incomplete dominance 3. Multiple genes
- 17. Complete dominance One of the contrasting character of the parents, dominates in the hybrid by masking the other character. Example: Height of the pea plant (Pisum sativum L.)
- 18. Tall pea plant X Dwarf pea plant -Parent phenotype TT X tt - parent genotype T X t - Parent gametes Tt -F1 hybrid: all are Tall plants
- 19. Incomplete dominance In incomplete dominance, both alleles of a character express their character in the F1 generation. So, the F1 individual has an intermediate character between the parents or F1 hybrid fails to express dominant character, this is because of incomplete dominance. So, both the genes are called Co-dominance. Example: Flower colour in 4’O Clock plant. (Mirabilis jalapa L.)
- 20. Red X White - Parent phenotype RR X rr - Parent genotype R X r - Parent gametes Rr - F1 Hybrid, All are pink flowered plants F1 plants are subjected to self fertilization Pink X Pink -F1 phenotype Rr X Rr -F1 genotype Red : Pink : White -Phenotypic ratio 1 : 2 : 1 Gametes R r R RR Red Rr Pink r Rr Pink rr White
- 21. Multiple factor inheritance It is a kind of different dominant gene interaction, in which more than two different dominant genes effect the same character of an organism in commutative fashion. Such a type of gene interaction results in 1:4:6:4:1 in the F2 generation. Since multiple gene interaction includes the inheritance of many gene controlling the same character it is also called polygenic interaction. Since polygenic interaction results in change in the quantitative expression of the same character is also called quantitative expression. Example: Pericarp colour or grain colour in wheat (Triticum aestivum L.)
- 22. Deep red X White - Parent phenotype R1R1R2R2 X r1r1r2r2 - Parent genotype R1R2 X r1r2 - Parent gametes R1r1R2r2 - F1 hybrid; all are Reddish in colour F1 plants are subjected to self fertilization Reddish X Reddish - F1 Phenotype R1r1R2r2 X R1r1R2r2 - F1 Genotype R1R2 R1r2 r1R2 r1r2 X R1R2 R1r2 r1R2 r1r2 - F1 Gametes Deep red: Red: Reddish: Light red: White - Phenotypic ratio 1 : 4 : 6 : 4 : 1 Gametes R1R2 R1r2 r1R2 r1r2 R1R2 R1R1R2R2 Deep red R1R1R2r2 Red R1r1R2R2 Red R1r1R2r2 Reddish R1r2 R1R1R2r2 Red R1R1r2r2 Reddish R1r1R2r2 Reddish R1r1r2r2 Light red r1R2 R1r1R2R2 Red R1r1R2r2 Reddish r1r1R2R2 Reddish r1r1R2r2 Light red r1r2 R1r1R2r2 Reddish R1r1r2r2 Light red r1r1R2r2 Light red r1r1r2r2 White
- 23. Conclusion The phenomenon in which a single gene controls one character in Mendel’s laws of inheritance, but various exceptions has been noticed in which different types of interaction are possible between the genes. The complete concept of gene interaction was suggested by Bateson and this concept is called Bateson’s factor hypothesis. Gene interaction is the influence of allelic or non-allelic genes on normal phenotypic expression of the trait. In other words, cases where two genes of the some allelic pair or genes of two or more different allelic pairs influence one another is called gene interaction.
- 24. Reference 1. Meyyan R.P, 2017, Genetics, Seventh edition, SaraS Publication, Nagercoil. 2. Verma P. S. and Agarwal V. K, 2010, genetics, S. Chand Publication, New Delhi. 3. Sundara Rajan S, 2007, College botany, volume-5, Himalaya publishing house, Bangalore.
- 25. Thank you…