20.3 Dihybrid Inheritance

Question 1

Define dihybrid inheritance. (1 mark)

Answer 1

The inheritance of two characteristics controlled by different genes.

Question 2

Y- yellow seeds
y- green seeds
R- round seeds
r- wrinkled seeds
What characteristic do the pees have if they are YyRr? (1 mark)

Answer 2

Yellow, round seeds.

Question 3

Y- yellow seeds
y- green seeds
R- round seeds
r- wrinkled seeds
What characteristic do the pees have if they are yyRr? (1 mark)

Answer 3

green, round seeds

Question 4

Y- yellow seeds
y- green seeds
R- round seeds
r- wrinkled seeds
What characteristic do the pees have if they are YYrr? (1 mark)

Answer 4

Yellow, wrinkled seeds

Question 5

Why might expected ratios of offspring be different from reality? (2 marks)

Answer 5

Fertilisation is random
If crossing over does not happen, then the two characteristics will always be inherited together.