A cross is done in Neurospora. The details are as follows:
+ ; + x f ; p
The +/f locus is quite close to the centromere on chromosome 7. The +/p locus is on chromosome 5 at a distance in which an average of 12% second division segregations occur.
The f locus is linked to the centromere and segregates only at the first division. The p locus segregates at the first division 88% of the time and segregates at the second division 12% of the time.
a) All octads will show segregation in Meiosis I for the +/f gene. 88% of octads will show segregation in Meiosis I for the +/p gene. Since the genes are unlinked, parental ditype (PD) = non-parental ditype (NPD). Hence, half of all octads that meet this condition would be parental ditype. Half of 88 would be 44%.
b) The proportion of octads having non-parental ditype (NPD) with segregation at Meiosis I for both loci will be 44%. Since PD = NPD, the answer will be the same for both PD and NPD.
c) The proportion of octads that are tetratypes showing a pattern of segregation at Meiosis I for +/f and a Meiosis I second division segregation pattern for +/p would be 12%. Since +/f does not have second division segregation in Meiosis I, all the octads showing patterns of segregation of second divisions would be +/p.
d) The proportion of tetratypes showing a second division pattern for +/f would be 0% since this does not occur with +/f. The pattern of segregation at Meiosis I for +/p would be 88%.