If the two characteristics that Mendel looked at in his dihybrid cross of smooth yellow peas with wrinkled green peas had been controlled by genes that were located close together on the same chromosome, then the F2 generation .

a) would have contained four phenotypes in a 9:3:3:1 ratio
b) would have contained only individuals that were heterozygous at both loci
c) would have deviated from the 9:3:3:1 phenotypic ratio
d) would have contained no individuals that were heterozygous at both loci

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organ system-an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.