Biology 9700 · AS & A Level · Infectious diseases

Infectious diseases — practice question

(a(i))[1]

Name the bacterium responsible for cholera.

(a(ii))[2]

Describe how cholera is transmitted from an infected individual to a person who is not infected.

(a(iii))[2]

Suggest and explain why cholera outbreaks are frequent following natural disasters.

(b(i))[2]

Explain how a substitution mutation can cause the amino acid sequence of a polypeptide to change.

(b(ii))[2]

The antibiotic nalidixic acid inhibits an enzyme needed for DNA replication in the bacteria that cause cholera. The gene $gyrA$ codes for this enzyme. A substitution mutation in this gene leads to resistance to nalidixic acid. Suggest how a change in the enzyme’s amino acid sequence produces antibiotic resistance.

(c)[4]

Some strains of the bacteria that cause cholera are resistant to more than one antibiotic (multiple resistance). Discuss the effects of multiple resistance on health authorities.

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: $\textit{Vibrio cholerae}$

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