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GENETICS

Powerpoint Presentation: Dihybrid Cross

DIHYBRID CROSS: TEST CROSS

In monohybrid crosses, to know if a dominant trait is homozygous (RR) or heterozygous (Rr) it is necessary to carry out a test cross. This is done with a homozygous recessive (rr) individual. The same is true for a dihybrid cross where the test cross is made with an individual which is homozygous recessive for both characters (rryy).

Phenotypes

Round Yellow      x     Wrinkled Green

Genotypes

RrYy

rryy

Gametes

RY, Ry, rY, ry

ry

Genotypes
  RY Ry rY ry
ry RrYy Rryy rrYy rryy
Phenotypes Round Yellow

Round Green

Wrinkled Yellow

Wrinkled Green

Ratios 1/4 or 25% 1/4 or 25% 1/4 or 25% 1/4 or 25%

 

 

 

 

 

 

 

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© Paul Billiet 2012