A mutation in the gene $\textit{MT-RNR1}$ is present in some children. If gentamicin is given to children with this mutation, deafness can occur. Before gentamicin is given to a child with a severe bacterial infection, PCR (polymerase chain reaction) and electrophoresis are used to check whether the child has this mutation. If the mutation is detected, a different antibiotic must be used.
Describe and explain how $\textit{Taq}$ polymerase functions in PCR.
PCR with primers specific to the $\textit{MT-RNR1}$ gene is used to amplify DNA from the child being tested. The PCR primers are designed so that the amplified product of the normal allele of $\textit{MT-RNR1}$ is longer than the amplified product of the mutant allele. Gel electrophoresis is used to separate the PCR products. Fig. 3.1 shows the gel electrophoresis results after this PCR method has been carried out on DNA samples from three children. State which of the children in Fig. 3.1 cannot receive the antibiotic gentamicin to treat a severe bacterial infection.
Explain how gel electrophoresis produces the pattern of results shown in Fig. 3.1 from the PCR products of the $\textit{MT-RNR1}$ gene.
Certain bacteria possess plasmids that carry a gene giving resistance to gentamicin. The gene can be passed to other bacteria. Suggest how the gentamicin-resistance gene can be transferred to other bacteria.
State which of the children in Fig. 3.1 cannot receive the antibiotic gentamicin to treat a severe bacterial infection.
Explain how gel electrophoresis produces the pattern of results shown in Fig. 3.1 from the PCR products of the $MT$-$RNR1$ gene.