88. During fusion of Rat and Human cell it was found that chromosomes of one species was selectively eliminated, this had opened new doors to study
(1) Transgenic study
(2) Chromosomal incompatibility
(3) Gene physical mapping
(4) Dominance of genes
Selective elimination of one species’ chromosomes during rat-human cell fusion, typically human chromosomes in rodent hybrids, creates cells retaining specific chromosomes linked to genetic markers. This phenomenon occurs due to DNA repair defects and instability post-fusion, allowing correlation of retained chromosomes with expressed genes.
Option Analysis
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(1) Transgenic study: Transgenic research introduces foreign genes into organisms using vectors like Ti plasmid, not relying on chromosome loss in hybrids. Fusion aids hybrids but not stable germline transgenics.
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(2) Chromosomal incompatibility: Describes observed elimination but does not specify the study’s purpose. Incompatibility explains mechanism, not application.
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(3) Gene physical mapping: Retained chromosomes express species-specific enzymes, mapping loci to chromosomes via synteny. Human-rodent hybrids assigned genes pre-sequencing.
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(4) Dominance of genes: Examines allele interactions within diploid cells, unrelated to interspecies hybrid chromosome loss. Dominance applies to inheritance, not mapping.
Correct Answer and Explanation
The correct option is (3) Gene physical mapping. Hybrids selected in HAT medium retain variable human chromosomes, assayed for enzymes like G6PD (X-linked), assigning genes to chromosomes. Rat-human fusions followed human-mouse success, advancing somatic cell genetics
