Answer
In Str analysis if the gene has hommozygous alleles then there would be only one peak shown in the electrophoretogram. And two peaks will be shown if the gene is heterozygous. And there can be DNA or Allele drop out when too little DNA is amplified because of Stochastic effect which makes the heterozygous sample appear falsely homozygous. Allelic dropout is a commonly observed source of missing data in microsatellite genotypes, in which one or both allelic copies at a locus fail to be amplified by the polymerase chain reaction. Especially for samples with poor DNA quality, this problem causes a downward bias in estimates of observed heterozygosity and an upward bias in estimates of inbreeding, owing to mistaken classifications of heterozygotes as homozygotes when one of the two copies drops out Other possiblity is the presence of Null allele. Allele is present in the DNA sample but fails to be amplified due to a nucleotide change in a primer binding site.
Work Step by Step
In Str analysis if the gene has hommozygous alleles then there would be only one peak shown in the electrophoretogram. And two peaks will be shown if the gene is heterozygous. And there can be DNA or Allele drop out when too little DNA is amplified because of Stochastic effect which makes the heterozygous sample appear falsely homozygous. Allelic dropout is a commonly observed source of missing data in microsatellite genotypes, in which one or both allelic copies at a locus fail to be amplified by the polymerase chain reaction. Especially for samples with poor DNA quality, this problem causes a downward bias in estimates of observed heterozygosity and an upward bias in estimates of inbreeding, owing to mistaken classifications of heterozygotes as homozygotes when one of the two copies drops out Other possiblity is the presence of Null allele. Allele is present in the DNA sample but fails to be amplified due to a nucleotide change in a primer binding site.
