Question

The data below shows our complementation tests' results. "+" indicates complementation between the two strains and "-" indicates no complementation. Please ignore the empty boxes.

	1	2	3	4	5	6	7	8
1	-	+	+	+	-	+	-	+
2		-	+	+	+	+	+	+
3			-	+	+	-	+	-
4				-	+	+	+	+
5					-	+	-	+
6						-	+	-
7							-	+
8								-

Q1: Using designations “Group A”, “Group B,” etc., organize the mutant strains into complementation groups. If the result of any cross does not fit your groupings, indicate which cross(es) you have excluded.

Q2: Consider the consequence if one of the mutations was dominant. You should see that complementation tests could not be used to provide information about dominant mutations.

a) If a mutation were dominant, how would the diploid be affected? What effect would this have on the determination of your complementation groups?

b) How would you test if any of these trp^- mutations were dominant?

Answer 1

Q1: Remember that a positive result between 2 strains indicates that the mitations are in different genes. So we are going to group the strains by the gene affected:

Group A: 1, 5, 7

Group B: 3, 6, 8

Group C: 2

Group D: 4

Each group represents a single gene. Strains 2 and 4 have an affected gene that is not affected in any other strain

Q2:

a) If one of this mutations was dominant then we would have a wrong reading, since it will show a negative result while it could be positive. Complementation cannot be done if there are dominant mutations, since its results would not be relyable

b) A way to test if the mutation is dominant is to make a cross of this mutant with a wildtype strain. If the mutation is recessive then the results will show wildtype expression, but if the mutation is dominant the results will show blocked expression