Question

What is NOT true with regard to FAP (familial adenomatous polyposis)?

• A. C-myc gene expression decreased
• B. Antibodies to normal mucin
• C. Due to defect in the FAP gene
• D. Proliferation of colonic epithelium

Hint:

APC loss raises beta catenin/TCF activity, which increases c-myc, not decreases it.

Answer 1

The Correct Option is A

FAP comes from a germline defect in the APC gene. Losing working APC protein frees up beta catenin, and this shift changes several downstream genes, including c-myc. Let's check each statement against that biology.

1. C-myc gene expression decreased: This is false. Loss of APC lets beta catenin build up and turn on c-myc, so c-myc expression rises rather than falls.
2. Antibodies to normal mucin: FAP patients have been found to carry antibodies against normal colonic mucin, so this statement holds true.
3. Due to defect in the FAP gene: True by definition, FAP is caused by a mutated APC/FAP gene inherited in an autosomal dominant pattern.
4. Proliferation of colonic epithelium: True, unchecked epithelial growth is exactly what produces the hundreds of adenomatous polyps seen in FAP.

Three of the four statements match accepted FAP biology. Only the claim of decreased c-myc expression goes against the known increase caused by unopposed beta catenin/TCF signalling.

Let's summarize:

• APC loss raises, not lowers, c-myc expression through beta catenin/TCF signalling.
• The other three statements about FAP are accepted as correct.

The statement that is NOT true is the claim of decreased c-myc gene expression.