Conversion in gene b1 of Ascobolus: Polarity of 6:2 and inverted polarity of aberrant 4:4 segregations.

Thirteen mutations located in gene b1 of Ascobolus immersus were studied for their non-mendelian segregation patterns. All these motations yield post-meiotic segregations. The non-mendelian segregation frequencies are the highest for the left end mutations. From left to right, the frequency of aberrant 4:4 asci increases. The hybrid DNA formation and distribution pattern as deduced from this result is consistent with that previously found in gene b2, providing further support to the Aviemore model. The frequency of 6:2 asci decreases from left to right. This constitutes an entirely new observation, the meaning of which is discussed.