Microbiology, 2021

430 11 • Mechanisms of Microbial Genetics
Figure 11.18
Mutations can lead to changes in the protein sequence encoded by the DNA.
CHECK YOUR UNDERSTANDING
• What are the reasons a nucleotide change in a gene for a protein might not have any effect on the
phenotype of that gene?
• Is it possible for an insertion of three nucleotides together after the fifth nucleotide in a protein-coding
gene to produce a protein that is shorter than normal? How or how not?
MICRO CONNECTIONS
A Beneficial Mutation
Since the first case of infection with human immunodeficiency virus (HIV) was reported in 1981, nearly 40
million people have died from HIV infection, 2 the virus that causes acquired immune deficiency syndrome
(AIDS). The virus targets helper T cells that play a key role in bridging the innate and adaptive immune
response, infecting and killing cells normally involved in the body’s response to infection. There is no cure for
HIV infection, but many drugs have been developed to slow or block the progression of the virus. Although
individuals around the world may be infected, the highest prevalence among people 15–49 years old is in sub-
Saharan Africa, where nearly one person in 20 is infected, accounting for greater than 70% of the infections
worldwide 3 (Figure 11.19). Unfortunately, this is also a part of the world where prevention strategies and drugs
to treat the infection are the most lacking.
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