Explain why some plasmids contain a gene for resistance to an antibiotic

I’m doing some practice exam questions for biology, and i’m not sure how to do these 3 parts to the question.

Nucleic acids offer variability because they contain alternate forms of genes called .

Define the apical impulse and describe its normal location, size, and duration. which abnormal conditions may affect the location of the apical impulse? explain the mechanism producing normal first and second heart sounds. describe the effect of respiration on the heart sounds. describe the characteristics of the first heart sound and its intensity at the apex of the heart and at the base. describe the characteristics of the second heart sound and its intensity at the apex of the heart and at the base.