8.1 4 Dihybrid inheritance of unlinked genes

Question 1

Digenic crosses

Answer 1

Breeding experiments involving the inheritance of two pairs of contrasting characteristics at the same time

Question 2

Remember

Answer 2

Determine possible gametes

Question 3

Parental phenotypes

Answer 3

Offspring that have the same phenotypes as the parental organisms

Question 4

Recombinant phenotypes

Answer 4

Describes offspring that have different phenotypes to their parents as a result of recombination of chromosomes during sexual reproduction

Question 5

Crossing of two non-linked heterozygotes in a dihybrid cross

Answer 5

9:3:3:1

Question 6

When don’t get ratios expect

Answer 6

Small sample size
Experimental errors - can escape or die relatively easily
Process is random sometimes the unexpected happens
Unexpected ratios can mean the genes being examined are both on the same chromosome (they are linked )

Question 7

Chi squared test

Answer 7

Establish whether any differences between observed and expected results are significant or not - are they simply due to chance

Question 8

Table for chi squared test

Answer 8

Phenotype 
Hypothesis 
Observed 
Expected 
O-E 
(O-E)^2
(O-E)^2/E
Total to get x^2

Question 9

How to calculate degrees of freedom for chi squared test

Answer 9

Degrees of freedom=no categories -1

Accept null if below degrees of dreeeom