Is sickle cell gene mutation positive, negative, or neutral?

The direct energy source that drives atp synthesis during respiratory oxidative phosphorylation is

Pl as time goes by and water goes through the water cycle again and again, the amount of water on earth: increases decreases ostays the same goes up and down

During crossing-over, a. genetic material is exchanged between nonsister chromatids, resulting in new combinations of alleles. b. nonsister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. c. one homologous chromosome of a tetrad is exchanged with another tetrad, resulting in new combinations of alleles. d. sister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. e. genetic material is exchanged between sister chromatids, resulting in new combinations of alleles.