McClintock

McClintock, B. 1953. Induction of instability at selected loci in maize. Genetics 38:579-599.

McClintock showed that instead of a crossover between a chromosome with a duplicate segment and a normal chromosome causing the breakage-bridge-fusion cycle, a gene called Ds could also create breakage of a chromosome arm. The sticky ends created by a break, due to the Ds element, would fuse and initiate the breakage-bridege-fusion cycle. The breakage-bridge-fusion cycle initiated by the Ds element caused variegated sectors in endosperm tissue, due to unequal breaks in dicentric chromosomes. The Ac element was necessary to activate a break at the Ds locus.

McClintock, B. 1950. Mutable loci in maize Carnegie Institute of Washington Yearbook 49:157-167.

Chromosome 9 of maize with marker loci on the short arm

Ds - this is the allele that can cause dissociation or
Ds - chromosome breakage.

Ac - the activator allele activates the Ds allele.

Wx - The dominant allele results in normal starchy
Wx - endosperm; the recessive (wx) allele results
Wx - in waxy endosperm when homozygous.

Bz - Purple anthocyanin pigment in plant and aleurone
Bz - layer of the kernel; the recessive allele (bz) produces
Bz - bronze color in the plant tissue and kernel.

Sh₁ - The dominant allele results in normal development
Sh₁ - of the endosperm; the recessive allele (sh₁) results
Sh1 - in shrunken endosperm.

I - The dominant allele (I) inhibits purple anthocyanin
I - color and the kernel is yellow; the C allele produces
I - purple aleurone; the recessive c allele produces yellow
I - aleurone.