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History of genetics
Learn introductory genetics with Braimy- B.Sc agriculture
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a) Novel Phenotype (9:3:3:1):

  • A novel phenotype is a phenotype that is concerned with the unique visual appearance of an organism as compared with its parents.
  • Eg: comb shape in poultry
  • New phenotype results from interaction between dominants and also from both homozygous recessives.

How plasticity can facilitate the evolution of a novel, complex... |  Download Scientific Diagram

b) Epistasis:

  • Epistasis is a circumstance where the expression of one gene is affected by the expression of one or more independently inherited genes.
  • For example, if the expression of gene #2 depends on the expression of gene #1, but gene #1 becomes inactive, then the expression of gene #2 will not occur.

Epistasis - Wikipedia

  • These are following types:

i) Complementary action (9:7):

  • Two genes may be required to produce the same effect.
  • Eg: Flower color in sweet pea.

ii) Inhibiting action (13:3):

  • One gene may act as an inhibitor of the effect of another gene.
  • Eg: aleurone color in maize.

iii) Duplicating action (15:1):

  • Either of 2 gene may produce a similar effect or the same effect is produced by both of them together.
  • Eg: Seed capsules of Bursa.

iv) Modifying action ( 9:3:4):

  • One gene has no visible effect unless a second gene is present at another locus.
  • Eg: Grain color in maize.

v) Additive or polymeric action (9:6:1):

  • Two gene may produce the same effect, but the effects are additive if both genes are present.
  • Eg: awn in barley.

vi) Masking action (12:3:1):

  • One gene may hide the effect of a second gene when both are present.
  • Eg: Seed coat color in barley.
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