CIE IGCSE Biology Unit 15: Drugs

Drug

any substance taken into the body that modifies or affects chemical reactions in the body

complete course of antibiotics

prevents bacteria from undergoing mutation And

Developing resistance

Why antibiotics kill bacteria, but do not affect viruses

Antibiotics dissolve the cell wall of the bacteria and contents of bacteria leak out, as virus is not a cell, it does not affect viruses

EFFECT OF MRSA

Where bacteria undergo mutation

Where there is a change in base sequence of DNA producing new allele

Selection pressure is antibiotic

resistant will replicate and pass on mutant allele ( resistant allele ) to the

coming offsprings

Increasing the frequency of the resistant allele in population

By natural selection

Bacteria reproduces quickly