NONDETECTABILITY OF RESTRICTION FRAGMENTS AND INDEPENDENCE OF DNA FRAGMENT SIZES WITHIN AND BETWEEN LOCI IN RFLP TYPING OF DNA

Citation
R. Chakraborty et al., NONDETECTABILITY OF RESTRICTION FRAGMENTS AND INDEPENDENCE OF DNA FRAGMENT SIZES WITHIN AND BETWEEN LOCI IN RFLP TYPING OF DNA, American journal of human genetics, 55(2), 1994, pp. 391-401
Citations number
47
Categorie Soggetti
Genetics & Heredity
ISSN journal
00029297
Volume
55
Issue
2
Year of publication
1994
Pages
391 - 401
Database
ISI
SICI code
0002-9297(1994)55:2<391:NORFAI>2.0.ZU;2-X
Abstract
We provide experimental evidence showing that, during the restriction- enzyme digestion of DNA samples, some of the HaeIII-digested DNA fragm ents are small enough to prevent their reliable sizing on a Southern g el. As a result of such nondetectability of DNA fragments, individuals who show a single-band DNA profile at a VNTR locus may not necessaril y be true homozygotes. In a population database, when the presence of such nondetectable alleles is ignored, we show that a pseudodependence of alleles within as well as across loci may occur, Using a known sta tistical method, under the hypothesis of independence of alleles withi n loci, we derive an efficient estimate of null allele frequency, whic h may be subsequently used for testing allelic independence within and across loci. The estimates of null allele frequencies, thus derived, are shown to agree with direct experimental data on the frequencies of HaeIII-null alleles. Incorporation of null alleles into the analysis of the forensic VNTR database suggests that the assumptions of allelic independence within and between loci are appropriate. In contrast, a failure to incorporate the occurrence of null alleles would provide a wrong inference regarding the independence of alleles within and betwe en loci.