A conditional mutation expresses its mutant phenotype only under certain conditions (the restrictive conditions) and expresses the normal phenotype under other conditions (the permissive conditions). One type of conditional mutation is a temperature-sensitive mutation, which expresses the mutant phenotype only at certain temperatures. Strains of E. coli have been isolated that contain temperature-sensitive mutations in genes encoding different components of the replication machinery. In each of these strains, the protein produced by the mutated gene is nonfunctional under the restrictive conditions. You grow these strains under the permissive conditions and then abruptly switch them to the restrictive conditions. After one round of replication under the restrictive conditions, you isolate DNA from each strain and analyze it. What characteristics would you expect to see in the DNA isolated from a strain with a temperature-sensitive mutation in the gene that encodes each of the following proteins? a. DNA ligase b. DNA polymerase I c. DNA polymerase III d. Primase e. Initiator protein
A conditional mutation expresses its mutant
certain conditions (the restrictive conditions) and expresses the normal
phenotype under other conditions (the permissive conditions). One type
of conditional mutation is a temperature-sensitive mutation, which
expresses the mutant phenotype only at certain temperatures.
Strains of E. coli have been isolated that contain temperature-sensitive
mutations in genes encoding different components of the replication
machinery. In each of these strains, the protein produced by the mutated
gene is nonfunctional under the restrictive conditions. You grow these
strains under the permissive conditions and then abruptly switch them to
the restrictive conditions. After one round of replication under the
restrictive conditions, you isolate DNA from each strain and analyze it.
What characteristics would you expect to see in the DNA isolated from
a strain with a temperature-sensitive mutation in the gene that encodes
each of the following proteins?
a. DNA ligase
b. DNA polymerase I
c. DNA polymerase III
d. Primase
e. Initiator protein
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