A fungal infection occurs in a patient. The organism's cell wall contains:

A. Deletion: A deletion mutation removes one or more nucleotides from the DNA sequence. While deletions can lead to frameshifts and potentially premature stop codons, the key feature in this scenario is the introduction of a stop signal, not the removal of nucleotides per se.

B. Nonsense: A nonsense mutation changes a codon that encodes an amino acid into a stop codon. In this example, “THE CAT ATE THE BIG RAT” is truncated to “THE CAT ATE (stop),” indicating translation terminates prematurely. This type of mutation produces a truncated, usually nonfunctional protein.

C. Silent: A silent mutation changes a nucleotide without altering the amino acid sequence. It does not produce a stop codon or truncate the protein, so it would not result in “THE CAT ATE (stop).”

D. Missense: A missense mutation changes a codon so that a different amino acid is incorporated. While it alters the protein sequence, it does not introduce a stop codon, so it cannot account for the premature termination seen here.

E. Insertion: An insertion adds one or more nucleotides into the sequence. Like deletions, insertions can cause frameshifts that might eventually produce a stop codon, but the defining characteristic in this example is the direct conversion of a codon to a stop codon, making this a nonsense mutation rather than a generic insertion.

A. facilitated diffusion: Facilitated diffusion is the movement of substances across a cell membrane via specific carrier proteins or channels, but it occurs along the concentration gradient (from high to low) and does not require cellular energy. It relies on the natural kinetic energy of molecules rather than ATP.

B. endocytosis: Endocytosis involves the engulfing of large particles or liquids by the cell membrane to bring them into the cell. Although it requires energy, it is a bulk transport mechanism rather than the specific movement of molecules against a concentration gradient using a carrier protein.

C. active transport: Active transport is the movement of molecules against their concentration gradient (from lower to higher concentration) using specific transport proteins and energy expenditure, typically in the form of ATP. Examples include the sodium-potassium pump and calcium pumps in cell membranes, which maintain essential ionic gradients for cell function.

D. osmosis: Osmosis is the passive movement of water molecules across a semipermeable membrane from an area of low solute concentration to high solute concentration. It does not require energy or a carrier protein and is specific to water movement.

E. diffusion: Diffusion is the passive movement of molecules from an area of higher concentration to lower concentration down their concentration gradient. It does not require energy or proteins and is driven by molecular motion, unlike active transport which moves substances against the gradient.