Question

An important criterion often used for establishing disease causality associated with a microbe is to provide evidence for the presence of the microbe at the infection site. Indianius hooziskerious is a heinous pathogen that infects humans and causes blotchy crimson and cream spots on the skin of infected Illinois residents. The crimson and cream spots appear only if I. hooziskerious is present at the site of infection. To diagnose whether individuals are infected with I. hooziskerious. Professor T. Perry runs a powerhouse diagnostic lab for detecting the heinous pathogen Indianius hooziskerious. Her laboratory runs a PCR-based assay for detecting the presence of I. hooziskerious, that upon amplification, requires approximately 109 copies of the gene encoding I. hooziskerious 16s rRNA to be detected. Each cell of I. hooziskerious has one copy of the gene encoding 16s rRNA. When running the PCR test of a sample from an Illinois resident who had ventured by accident into Indiana, Professor Perry’s diagnostic test indicated that the gene encoding 16s rRNA of I. hooziskerious required 20 rounds of PCR amplification to be detected. Based on this information alone, approximately how many I. hooziskerious bacteria were present in the sample obtained from the infected Illinois resident?  
A) 40 bacteria
B) 10⁶ bacteria
C) 20 bacteria
D) 10⁹ bacteria
E) 10³ bacteria

Answer 1

The PCR based method requires 109 copies of the gene encoding I. hooziskerious 16s rRNA after amplificaiton. Now, as each cell of I. hooziskerious has one copy of the gene encoding 16s rRNA, there must be 109 cells will be present for the detection of the infection.

Now, as for the Illinois resident, 20 rounds of PCR amplification results in the presence of 16s rRNA of I. hooziskerious, thus we can conclude that there are 109 copies of gene are apmlified within this 20 round of PCR. AS bacteria is unicellular, we can say that there are

d)109 bacteria present in the pateint.