Practice question

A polymorphic restriction site present in only one allele creates length variation after digestion due to differential cleavage. Homozygous normal lacking extra site yields single uncut high-molecular-weight band representing full-length fragment. Homozygous polymorphic with site on both chromosomes yields two smaller cut bands after complete digestion. Heterozygous individual carries both chromosomes, one cleavable and one resistant, so digestion mixture contains both uncut and cut products. Electrophoresis therefore shows combined pattern containing both parental fragments diagnostic of heterozygosity, following Mendelian co-dominant inheritance of RFLP markers in population studies.