Garrod's concept regarding the relationship between the gene and metabolism can best be described as:
a. one gene - one polypeptide
b. one mutant gene - one metabolic block
c. one gene - one metabolism
d. one gene - one transcript

b. one mutant gene - one metabolic block

Explanation:

Garrod studied inborn errors of metabolism and explained the molecular causes of various genetic diseases such as albinism and alkaptonuria.

Accordingly, the individuals homozygous for the recessive allele exhibit metabolic defect responsible for the disease.

For example, alkapton is normally degraded into maleylacetoacetic acid by the reaction catalyzed by the enzyme homogentisic acid oxidase. A mutation in the respective gene produces nonfunctional enzyme and leads to alkaptonuria as the individuals are not able to degree alkapton in absence of functional enzyme.

Hence, one mutation blocks one metabolic pathway and leads to a genetic disorder.

as the gila monster consumes the eggs or young of the desert cottontail and gambel's quail, thus its main food supply is only accessible for a restricted time duration every year. however, for this, the gila monsters exhibit three adaptations, which elevate their survival rate in the desert condition.  

first, is that they possess huge bodies, and can consume greater concentrations of food during a small period. secondly, they require to feed infrequently as they can accumulate fat in their tails. ultimately, their rate of metabolism is very low, so that they can burn their reservoirs of fat gradually.