Nine rII− mutants of bacteriophage T4 were used inpairwise infections of E. coli K(λ) hosts. Six of themutations in these phages are point mutations; theother three are deletions. The ability of the doubly infected cells to produce progeny phages in large numbers is scored in the following chart.1 2 3 4 5 6 7 8 91 − − + + − − − + +2 − + + − − − + +3 − − + − + − −4 − + − + − −5 − − − + +6 − − − −7 − + +8 − −9 −The same nine mutants were then used in pairwise infections of E. coli B hosts. The production of progenyphages that can subsequently lyse E. coli K(λ) hosts isnow scored. In the table, 0 means the progeny do notproduce any plaques on E. coli K(λ) cells; − meansthat only a very few progeny phages produce plaques;and + means that many progeny produce plaques(more than 10 times as many as in the − cases).1 2 3 4 5 6 7 8 91 − + + + + − − + +2 − + + + + − + +3 0 − + 0 + + −4 − + − + + +5 − + − + +6 0 0 − +7 0 + +8 − +9 −a. Which of the mutants are the three deletions? Whatcriteria did you use to reach your conclusion?b. If you know that mutation 9 is in the rIIB gene,draw the best genetic map possible to explain thedata, including the positions of all point mutationsand the extent of the three deletions.c. One uncertainty should remain in your answer topart (b). How could you resolve this uncertainty?
Nine rII− mutants of bacteriophage T4 were used in
pairwise infections of E. coli K(λ) hosts. Six of the
mutations in these phages are point mutations; the
other three are deletions. The ability of the doubly infected cells to produce progeny phages in large numbers is scored in the following chart.
1 2 3 4 5 6 7 8 9
1 − − + + − − − + +
2 − + + − − − + +
3 − − + − + − −
4 − + − + − −
5 − − − + +
6 − − − −
7 − + +
8 − −
9 −
The same nine mutants were then used in pairwise infections of E. coli B hosts. The production of progeny
phages that can subsequently lyse E. coli K(λ) hosts is
now scored. In the table, 0 means the progeny do not
produce any plaques on E. coli K(λ) cells; − means
that only a very few progeny phages produce plaques;
and + means that many progeny produce plaques
(more than 10 times as many as in the − cases).
1 2 3 4 5 6 7 8 9
1 − + + + + − − + +
2 − + + + + − + +
3 0 − + 0 + + −
4 − + − + + +
5 − + − + +
6 0 0 − +
7 0 + +
8 − +
9 −
a. Which of the mutants are the three deletions? What
criteria did you use to reach your conclusion?
b. If you know that mutation 9 is in the rIIB gene,
draw the best genetic map possible to explain the
data, including the positions of all point mutations
and the extent of the three deletions.
c. One uncertainty should remain in your answer to
part (b). How could you resolve this uncertainty?
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