An ab Neurospora was crossed with an a + b + form. After meiosis, 1000 asci were
ID: 54280 • Letter: A
Question
An ab Neurospora was crossed with an a+b+ form. After meiosis, 1000 asci were dissected and produced the data listed in the table below. What is the linkage arrangement of these loci?
Ascus Number
Spore Number
1
2
3
4
5
6
7
1
a b
a b+
a b
a b
a b+
a+ b+
a b
2
a b
a b+
a b
a b
a b+
a+ b+
a b
3
a+ b+
a+ b
a b+
a+ b
a b+
a+ b+
a b
4
a+ b+
a+ b
a b+
a+ b
a b+
a+ b+
a b
5
a+ b
a+ b
a+ b+
a+ b+
a+ b
a b
a+ b+
6
a+ b
a+ b
a+ b+
a+ b+
a+ b
a b
a+ b+
7
a b+
a b+
a+ b
a b+
a+ b
a b
a+ b+
8
a b+
a b+
a+ b
a b+
a+ b
a b
a+ b+
70
32
225
25
10
315
323
Spore Number
1
2
3
4
5
6
7
1
a b
a b+
a b
a b
a b+
a+ b+
a b
2
a b
a b+
a b
a b
a b+
a+ b+
a b
3
a+ b+
a+ b
a b+
a+ b
a b+
a+ b+
a b
4
a+ b+
a+ b
a b+
a+ b
a b+
a+ b+
a b
5
a+ b
a+ b
a+ b+
a+ b+
a+ b
a b
a+ b+
6
a+ b
a+ b
a+ b+
a+ b+
a+ b
a b
a+ b+
7
a b+
a b+
a+ b
a b+
a+ b
a b
a+ b+
8
a b+
a b+
a+ b
a b+
a+ b
a b
a+ b+
70
32
225
25
10
315
323
Explanation / Answer
From the given data,
Thus, in this problem 7 different types of asci have been studied (the column head). On classifying these 7 types of asci into the above three groups, we get:
Thus, the linkage arrangement of these loci is:
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