Question: Most human obesity does not follow Mendelian inheritance patterns, because body fat content is determined by a number of interacting genetic and environmental variables. Insights into how specific genes function to regulate body fat content have come from studies of mutant, obese mice. In one mutant strain, tubby (tub), obesity is inherited as a recessive trait. A comparison of the DNA sequence of the tub+ (wild-type allele, or the nonmutated allele) and tub alleles has revealed a single base-pair change: within the transcribed region, a 5' G-C base paur has been mutated to a T-A base pair. The mutation causes an alteration of the initial 5' base of the first intron. Therefore in the homozygous tub/tub mutant, a longer transcript is found. Propose a molecular based explanation for how a single base changes causes a nonfunctional gene product to be product, why a longer transcript is found in the tub/tub mutants.