Suggest an explanation. suggest an explanation. unlike histidine imidazole binds to atp forming a fairly stable complex. atp binds to hemoglobin more strongly than does the atp-imidazole complex. imidazole, therefore, tends to increase oxygen affinity of hemoglobin by blocking the atp-hemoglobin interaction. in native hb, the binding of oxygen is actually hindered by the fact that pulling on helix f must move it against constraints within the molecule. in the imidazole replacement, there is no need to do the extra work of moving helix f. this difference shows up as a more favorable free energy for binding. imidazole is significantly more acidic (lower pka) than histidine. thus, at the ph of blood, native hemoglobin is more acidic than the imidazole replacement. this lowering in ph causes the oxygen affinity of the hemoglobin to increase. in native hemoglobin, the initial binding of one o2 to a heme group promotes the binding of o2 to the other heme site on the molecule. in the imidazole replacement, the initial binding of one o2 to a heme group promotes the binding of two o2 to the other heme sites on the molecule. this effectively increases the oxygen affinity of the hemoglobin.

In a hypothetical breed of dogs, coat color is controlled by two genes. there are six different coat colors in this breed: black, brown, cream, gray, silver, and tan. consider the following crosses. cross 1: black females from a lineage of all black dogs are crossed with brown males from a lineage of all brown dogs. f1 males and females are all black. when f1 are intercrossed, f2 males and females are black or brown. cross 2: black females from a lineage of all black dogs are crossed with tan males from a lineage where all males are tan and all females are cream. f1 males are black, f1 females are gray. when f1 are intercrossed, f2 males and females are black, brown, gray, or tan. cross 3: silver females from a lineage where all females are silver and all males are gray are crossed with brown males from a lineage of all brown dogs. f1 males and females are all gray. when f1 are intercrossed, f2 males are black, brown, gray, or tan, f2 females are cream, gray, silver, or tan. select the correct statements regarding the mode of inheritance of the coat color genes. a) both genes are x-linked. b) both genes are autosomal. c) one of the genes modifies the expression of the other gene. d) each gene has an additive effect on the intensity of coat color. e) each gene independently specifies three colors. f) one of the genes is autosomal, and the other is x-linked.