Question

Eight mutant bacteriophage strains cannot lyse a certain type of bacteria that can be lysed by wild-type bacteriophages. The mutant strains were allowed to infect the bacteria in a complementation test. A "+" indicates that lysis occurred with coinfection. A "-" indicates that lysis did not occur.

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

A cistron is defined by no complementation in the Answer: cis/trans configuration.

How many genes are mutated in this experiment? (Use a number not a word in the space) Answer

Which of the following strains below are defective in the same gene as strain 3? Answer yes if the strain is defective or no if it is not.

Strain	Defective
1	AnswerYesNo
2	AnswerYesNo
3	N/A
4	AnswerYesNo
5	AnswerYesNo
6	AnswerYesNo
7	AnswerYesNo
8	AnswerYesNo

Answer 1

During coinfection, the occurrence of lysis indicates that both the mutations are non-allelic i.e. they are located at different loci.
The non-occurrence of lysis indicates that both the mutations are allelic to each other i.e. they are located in the same locus.

A cistron is defined by non-complementation in the trans-configuration.

Number of genes mutated = Complementation groups = 3
i. 1 = 6
ii. 2 = 5 = 7
iii. 3 = 4 = 8

Strains 4 and 8 are defective in the same gene as that of strain 3.
Strain   Defective
1   No
2   No
3   N/A
4   Yes
5   No
6   No
7   No
8   Yes