Homework SourseSeveral haploid mutants are isolated all of which require co
Several haploid mutants are isolated, all of which require compound E for growth. The compounds (A to D) in the biosynthetic pathway to E are known, but their order is not known. Each compound is tested for its ability to support the growth of each mutant (1 to 6). In the following table a plus sign indicates growth and a minus sign indicates no growth:
Mutant
Compound tested
AB
C
D
E
1
+
+
-
+
+
2
-
-
-
-
+
3
-
+
-
+
+
4
+
+
-
+
+
5
-
-
-
+
+
6
-
+
-
+
+
What is the order of compounds from A to E in the pathway? At which point in the pathway is each mutant blocked?
| Mutant | Compound tested | ||||
| AB | C | D | E | ||
| 1 | + | + | - | + | + |
| 2 | - | - | - | - | + |
| 3 | - | + | - | + | + |
| 4 | + | + | - | + | + |
| 5 | - | - | - | + | + |
| 6 | - | + | - | + | + |
Solution
It is well known that a pathway proceeds in order and any mutation in genes controlling specific steps required would cause the inhibition of growth in the mutant. We can observe the following in the table given
We can conclude that the order of intermediate compounds in the biosynthesis of E is in the order C, A, B, D, E.
