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#Southern blot

2 public questions tagged with this topic.

Molecular Marker

In a Southern blot analysis for parentage with STR, which offspring match both parents?

Parentage testing by Southern blotting of short tandem repeats relies on principle that offspring must inherit one allele from each parent. True biological offspring display bands matching maternal and paternal alleles, with at least one band shared with each parent. Offspring lacking paternal specific bands or showing novel bands inconsistent with Mendelian inheritance are excluded. In this blot, several progeny exhibit complementary banding patterns containing maternal and paternal specific fragments, confirming parentage, while mismatched profiles indicate exclusion or mutation, essential for pedigree verification.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Restriction Digestion & Mapping

Southern blot using probe between site 2 and 3 in heterozygous mutation shows:

In heterozygous individual carrying one wild-type allele retaining all three restriction sites and one mutant allele lacking recognition site between regions 2 and 3, digestion produces two different fragment lengths spanning probe region due to allele-specific cleavage. Southern blotting with a probe hybridizing between site 2 and 3 detects both alleles because probe sequence exists in both chromosomes regardless of cleavage status. Homozygous wild type would show one smaller band, homozygous mutant one larger band. Heterozygote displays both bands simultaneously, illustrating co-dominance of RFLP markers used in carrier screening and linkage analysis.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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