In Neurospora,the Genes His2 and Leu2 Are Closely Linked

Multiple Choice

In Neurospora,the genes his2 and leu2 are closely linked.From a cross,his2 × leu2,which is a rare octad of the following type,arose: his2, +
his 2. +
his 2. +
his 2, +
abort
abort
+, leu2
+, lou 2
This octad most likely arose by:

A) crossover between his2 and leu2,followed by first-division nondisjunction.
B) first-division nondisjunction.
C) post-meiotic mitotic nondisjunction.
D) rare triploidy.
E) second-division nondisjunction.