The phenotypic proportions in the progeny of the following crosses of auto-tetraploids in which the a+/a locus is very close to the centromere.
a) a+/a+/a/a x a/a/a/a
The gametes from these parents would be:
• 1/6 a+/a+
• 2/3 a+/a
• 1/6 a/a
• 1/6 a/a from homozygous recessive parent
Hence, the phenotypic ratio of the progeny would be 5 wild type [a+]: 1 a.
b) a+/a/a/a x a/a/a/a
The gametes from these parents would be:
• 1/2 a+/a
• 1/2 a/a
Hence, the phenotypic ratio of the progeny would be 1 wild type [a+]: 1 a.
c) a+/a/a/a x a+/a/a/a
The gametes from these parents would be:
• 1/2 a+/a
• 1/2 a/a
• 1/2 a+/a
• 1/2 a/a
Hence, the phenotypic ratio of the progeny would be 3 wild type [a+]: 1 a.
d) a+/a+/a/a x a+/a/a/a
The gametes from these parents would be:
• 1/6 a+/a+
• 2/3 a+/a
• 1/6 a/a
• 1/2 a+/a
• 1/2 a/a
Hence, the phenotypic ratio of the progeny would be 11 wild type [a+]: 1 a.