Q. 88 The nature of the polymorphic DNA fragment used for mapping is
(A) dominant.
(B) partial dominant.
(C) co-dominant.
(D) recessive
Understanding the Nature of Polymorphic DNA Fragments in Genetic Mapping
Polymorphic DNA fragments are essential tools in genetic mapping, revealing variations in DNA sequences across individuals. The correct answer to the query is (C) co-dominant, as these markers allow detection of both alleles in heterozygous samples.
Correct Answer
The nature of the polymorphic DNA fragment used for mapping is (C) co-dominant. Common markers like Restriction Fragment Length Polymorphism (RFLP) detect both alleles in a heterozygous individual, producing distinct fragment lengths for each. This co-dominance enables precise genotyping and linkage analysis in genetic maps.
Option Explanations
Polymorphic DNA markers vary in inheritance patterns based on detection methods.
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(A) Dominant: Markers like AFLP or RAPD show presence/absence of bands; heterozygotes appear identical to homozygotes, limiting mapping resolution.
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(B) Partial dominant: No standard category exists in molecular genetics for DNA fragments; this term applies more to intermediate phenotypes, not typical polymorphisms.
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(C) Co-dominant (Correct): RFLP and similar markers reveal both alleles via different fragment sizes, ideal for mapping as they distinguish homozygous from heterozygous states.
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(D) Recessive: Rare in DNA markers; recessive traits mask alleles phenotypically, but fragments are directly visualized, not masked.
Genetic Mapping Applications
Co-dominant markers excel in constructing linkage maps and QTL analysis due to heterozygote detection. RFLP, pioneered in 1980, uses restriction enzymes to generate polymorphic fragments for locus-specific mapping. This suits academic fields like plant genetics and population studies.
