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Presentation on Epistasis

Gene interactions occur when two or more different genes influence the outcome of a single trait

Epistasis is a phenomenon in which the expression of one gene depends on the presence of one or more modifier genes.

A gene whose phenotype is expressed is called epistatic.

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Presentation on Epistasis

  1. 1. PRESENTATION ON EPISTASIS PREPARED BY: Santosh pathak Bsc.AG IAAS, Lamjung
  2. 2. Epistasis  Gene interactions occur when two or more different genes influence the outcome of a single trait  Epistasis is a phenomenon in which the expression of one gene depends on the presence of one or more modifier genes.  A gene whose phenotype is expressed is called epistatic.  For example: If two epistatic genes A and B are mutated and each mutation by itself produces a unique phenotype but the two mutations together show the same phenotype as the gene A mutation then gene A is epistatic to gene B.  Epistasis can be contrasted with dominance, which is interaction between alleles at the same gene locus.
  3. 3. Types of epistasis 1.Complementary action(9:7) Two genes may be required to produce the same effect. e.g. flower color in sweet pea. 9 C_P_ : 3 C_pp :3 ccP_ : 1 ccpp purple white
  4. 4. 2.Inhibiting action(13:3) One gene may act as an inhibitor of the effect of another gene, e.g. aleurone color in maize. Parents: Red X White RRii rrII F1: RrIi(white) (selfing) F2: 9R-I-:white 3rrI-:white 1rrii:white 3R-ii:red
  5. 5. 3.Duplicating action(15:1) Either of two genes may produce a similar effect or the same effect is produced by both of them together. e.g. seed capsule of bursa. TTVV Triangular ttvv Ovate TtVv All triangular F1 (TtVv) x F1 (TtVv) TV Tv tV tV TV TV tV tv
  6. 6. 4.Modifying action(9:3:4) One gene has no visible effect unless a second gene is present at another locus. e.g. grain color in maize Parents: Purple X White PPRR pprr F1: PpRr (purple) (Selfing) F2: 9P-R-:purple 3ppR-:red 3P-rr:white 1pprr:white
  7. 7. 5.Additive/Polymeric action(9:6:1) Two genes may produce the same effect, but the effects are additive if both genes are present. e.g. awn in barley Parents: Long awn X Awnless AABB aabb F1: AaBb(long awn) (selfing) F2: 9A-B-:long awn 3A-bb:short awn 3aaB-:short awn 1aabb:awnless
  8. 8. 6.Masking action(12:3:1) One gene may hide the effect of a second gene when both are present. e.g. seed coat color in barley. Parents: Black X Yellow Bbyy bbYY F1: BbYy(black) (selfing) F2: 9B-Y-:black 3B-yy:black 3bbY-:yellow 1bbyy:white

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