Go back

14/15

SNPs within an individual

  • What do you think the very high level of diversity in one patient might indicate?
  • What about the smaller numbers of SNPs?
  • Does this have any implications for how we interpret genomic data regarding the probability of transmission?

»Show answers
» Hide answers

Feedback for Exercise 8

What do you think this large amount of diversity might indicate?

Large numbers of SNPs (> 400) could indicate that a second totally unrelated TB strain has infected the patient on top of the existing infection.

What about the smaller numbers of SNPs?

Smaller numbers of SNPs may indicate that the TB genomes are undergoing changes as the bacteria grow and divide within the human host – remember that TB infections can last for extended periods of time.

TB bacteria evolve by descent and researchers have estimated that TB genomes evolve at a rate of between 0.3 and 0.7 SNPs per genome per year.

Does this have any implications for how we interpret genomic data regarding the probability of transmission?

If an individual is infected with more than one TB strain, they may be able to transmit a “cloud” of different genomes. Genome sequencing can detect mixed infections but this depends on the prevalence of each strain within the host and the sampling methods used to select bacteria for DNA extraction.

» Continue