A company makes a genetically modified organism using an antibiotic resistance g

Question

A company makes a genetically modified organism using an antibiotic resistance gene (ampr) as a ‘marker’, to select transformed cells that were used to regenerate the whole organism. However, due to concerns about spreading resistance genes the new GMO faces a hard time from safety regulators. The developing company argues that there is no danger, because the resistance gene is not expressed. Evaluate this statement considering that the gene may not be expressed either because of epigenetic silencing or mutation.

Explanation / Answer

Antibiotics are important drug to control bacterial infection in any organism. It directly targets the bacterial functional or structural gene and reduces its expression. By creating mutation in any of the genes which is a potent target for antibiotic drug, the gene becomes resistant for that particular antibiotic. Later on antibiotic become ineffective. The new gene originated due to mutation is called as antibiotic resistance gene. Here antibiotic resistance gene (ampr) is selected as a marker. However the gene is not expressed in organism due to two possible reasons, Epigenetic silencing and Mutation.

Methylated DNA sequences cannot undergo process of transcription because it cannot be recognized by polymerase. Hence the gene is not expressed. DNA methylation, nucleosome- DNA interaction and histone modification are some of the major events of epigenetic changes. The sequence of gene is not mutated but the conformational changes in gene results in gene silencing.

Some random mutation can stops the expression of resistance gene. Lac of media nutrient, environmental condition for survival and temperature, are some major factor which can leads to random mutation. Deletion, duplication, translocation and inversions are some of the common type of mutations observed. Colonies contain marker gene (antibiotic resistance gene) are not observed possibly due to epigenetic silencing or mutation.      

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