8 mutant bacteriophage strains cannot lyse a certain type of bacteria that CAN b

Question

8 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 "+" symbol indicates that lysis has occurred with co-infection. A "-" symbol indicates that lysis did not occur.

1.) A cistron is defined by no complementation in the ____________ configuration.

a. cis

b. trans

2.) How many genes are controlling lysis in the bacteriophage? (place a number in this space) _________

3.) Which of the following strains are defective in the same strain as strain T? Answer yes OR no to each below.

G ______

K______

W______

T_______

M_______

A_______

Q_______

C_______

G K W T M A Q C G - + + - + + - + K - + + - + + - W - + + - + + T - + + - + M - + + - A - + + Q - + C -

Explanation / Answer

When two mutants are crossed and the resultant F1 progeny shows WT phenotype, it means that both the mutations are located in different genes. i.e. they are non-allelic.
When two mutants are crossed and the resultant F1 progeny shows mutant phenotype, it means that both the mutations are located in the same gene. i.e. they are allelic to each other.

In the given case,
'+' means lysis = WT phenotype = Both mutations are non-allelic
'-' means no lysis = mutant phenotype = Both mutations are allelic to each other

Complementation groups:
i. G = T = Q
ii. K = M = C
iii. W = A

1. A cistron is defined by no complementation in the trans configuration.
2. In the given case, there are three different genes controlling the cell lysis.
3. T = G = Q. There are two other mutations (G and Q) that are allelic to T.

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