Final answer:
Plasmids are mainly responsible for carrying antibiotic resistance genes and facilitating their transfer between bacteria, often through conjugation. Transposons also play a role in moving these genes between genomes, aiding the spread of resistance.
Step-by-step explanation:
The genetic elements primarily responsible for the acquisition of drug resistance genes and their transfer to bacteria are plasmids. Plasmids are small, circular pieces of DNA that exist and replicate independently of chromosomal DNA within bacteria. They can carry multiple antibiotic resistance genes and transfer them between bacteria through mechanisms of horizontal gene transfer, such as conjugation.
Conjugation is a process where two bacteria can connect and exchange genetic material, including antibiotic resistance genes. Transposons, which are DNA sequences that can change their position within the genome, can also move these resistance genes from one location to another, aiding the spread of resistance by allowing genes to move from chromosomes to plasmids. Once on a plasmid, these genes can be more easily exchanged among bacterial populations, increasing the prevalence of drug-resistant strains.