OCR A level biology Chapter 20 Epistasis and Linkage

______ ______ is the genetic occurrence in which two genes interact. One gene may 'suppress' another gene in the heterozygous combination.

• Epigenetics

• Dominant epistasis

• Genomics

• Recessive epistasis

For a heterozygous x heterozygous cross what would the phenotypic ratio be for a dominant epistatic gene for coloured squash plant.

• 9:3:3:1

  W:G:Y:B

• 9:6:1

  W:Y:G

• 3:9:4

  W:Y:G

• 12:3:1

  W:Y:G

So...W = Coloration Masked (white), w = Coloration gene 'unmasked'. Y = Yellow and y = green coloration. Which genotypes below would be WHITE in coloration?

• YyWW

• YYWw

• yyww

• Yyww

• YYww

So...W = Coloration Masked (white), w = Coloration gene 'unmasked'. Y = Yellow and y = green coloration. Which genotypes below would be Green in coloration?

• WWYy

• WwYY

• wwyy

• wwYy

• wwYY

So...W = Coloration Masked (white), w = Coloration gene 'unmasked'. Y = Yellow and y = green coloration. Which genotypes below would be Yellow in coloration?

• WWYy

• WwYY

• wwyy

• wwYy

• wwYY

So...W = Coloration Masked (white), w = Coloration gene 'unmasked'. Y = Yellow and y = green coloration. Which genotypes below would be YELLOW in coloration?

• yyWw

• yyww

• YyWW

• YYww

• Yyww

So...W = Coloration Masked (white), w = Coloration gene 'unmasked'. Y = Yellow and y = green coloration. Which genotype(s) below would be GREEN in coloration?

• yyWw

• yyww

• YyWW

• YYww

• Yyww

What is the color of the two parents? bbAa x BbAa

B = masking

b = No masking

A = yellow

a = green

• Yellow x White

• Yellow x Yellow

• White x Yellow

• Yellow x green

• green x yellow

What will be the ration of WHITE: YELLOW: GREEN offspring?

• 8 W: 6 Y: 2 G

• 8 W: 2 Y: 6 G

• 8 W: 4 Y: 4 G

• 6 W: 6Y: 4 G

• Some other ratio

Do you feel you understand the concept of Epistasis DOMINANT?

• Yes, Iḿ ready to move on.

• No, I need a bit of help.