Question at position 7 The mutant alleles of the CF gene that result in cystic fibrosis are recessive to normal alleles becausethe CF mutations that cause cystic fibrosis always result in no protein being produced.CF mutations result in a protein that has normal function only if normal CFTR protein also exists in the cell.dominant alleles that cause a fatal disorder, such as cystic fibrosis, cannot be inherited.the protein produced by the normal allele in heterozygotes is sufficient for normal cellular function.Clear my selection

Question

Question at position 7 The mutant alleles of the CF gene that result in cystic fibrosis are recessive to normal alleles becausethe CF mutations that cause cystic fibrosis always result in no protein being produced.CF mutations result in a protein that has normal function only if normal CFTR protein also exists in the cell.dominant alleles that cause a fatal disorder, such as cystic fibrosis, cannot be inherited.the protein produced by the normal allele in heterozygotes is sufficient for normal cellular function.Clear my selection

BlackTom AI · Accepted Answer

Question at position 7 asks about why mutant CF alleles are recessive to normal alleles in cystic fibrosis.
Option 1: 'the CF mutations that cause cystic fibrosis always result in no protein being produced.' This is not accurate because some CFTR mutations produce a protein with reduced or defective function rather than no protein at all. The phenotype can arise from loss of function but the statement as written overgeneralizes to 'always no protein,' which is incorrect.
Option 2: 'CF mutations result in a protein that has normal function only if normal CFTR protein also exists in the cell.' This mixes concepts: even with a normal allele present, if the mutant allele produces a nonfunctional protein, overall function is compromised. The key idea is not about requiring the normal protein to 'enable' mutant protein to function; rather, the normal allele can provide enough functional protein to maintain cellular function in heterozygotes, making this statement misleading.
Option 3: 'dominant alleles that cause a fatal disorder, such as cystic fibrosis, cannot be inherited.' This is factually wrong. A dominant lethal allele can be inherited and, if expressed early, may prevent reproduction, but the statement mischaracterizes inheritance patterns and CF is classically recessive, not due to the impossibility of inheritance of dominant lethal alleles.
Option 4: 'the protein produced by the normal allele in heterozygotes is sufficient for normal cellular function.' This correctly captures the classic explanation for CF being recessive: individuals with one normal CFTR allele (heterozygotes) produce enough functional CFTR protein to maintain normal function, so a single normal allele suffices to prevent the disease phenotype in many tissues.
Each option has been weighed for biological accuracy, distinguishing points about protein production, functional sufficiency, and inheritance patterns to clarify why the last statement aligns with the recessive nature of CF mutations.

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