Marker example, contd.
This figure shows the same marker assayed on 27 F2 progeny. Each carries either one of the two parental alleles, or has inherited one allele from each parent.
Remember, each plant does have 2 alleles. But, when they are both the same size, as in a homozygote, they run to the same position on the gel and so appear as one band.
Conventionally a “1” is assigned to one parental type, a “3” is assigned to the other parental type (typically the wild parent if there was one) and a “2” to the heterozygotes. Some software programs use A, B, and H instead.