Answer
Beneficial mutation: improves the bacterium’s ability to survive or reproduce (e.g., antibiotic resistance).
Harmful mutation: disrupts protein function and may reduce survival or kill the bacterium.
Work Step by Step
A mutation changes the sequence of nucleotides in DNA. Since DNA encodes proteins, a change in sequence can alter:
the amino acids in a protein,
the shape of the resulting protein,
the protein’s function.
Depending on how the protein changes, the mutation can be beneficial, harmful, or neutral.
Possible Benefits
A mutation can be beneficial if the new protein:
Performs its function better (e.g., works more efficiently in the cell).
Gives resistance to antibiotics (a very common beneficial mutation in bacteria).
Allows the bacterium to use a new nutrient source, making it more competitive.
Helps the bacterium survive stress, such as heat, toxins, or pH changes.
Possible Harms
A mutation can be harmful if:
The protein becomes nonfunctional or does not fold properly.
The gene product becomes toxic to the cell.
The mutation disrupts an essential pathway, such as DNA replication, metabolism, or cell wall formation.
The cell becomes more sensitive to antibiotics or environmental stress.
