Loss of heterozygosity (LOH) resulting from a crossover on the left arm of chromosome V.

<p>Diploid strains that are homozygous for the <i>ade2-1</i> mutation and have one copy of <i>SUP4-o</i> near the left end of V form pink colonies. A crossover between <i>SUP4-o</i> and <i>CEN5</i> (shown as an oval), followed by segregation of one recombinant and one non-recombinant chromosome into daughter cells (Segregation pattern 1), will result in a red/white sectored colony. If the two recombinant chromosomes segregate into one daughter cell, and the two non-recombinant chromosomes segregate into the other (Segregation pattern 2), no sectored colony is observed.