Which of the following statements best defines epistasis? O 1. We have epistasis when interacting genes do not show independent assortment
2. We have epistasis when identical genes produce different expression patterns in the same genotype and environment
3. We have epistasis when an allele at one locus masks the effects of one or more other alleles at the same locus
4. We have epistasis when an allele at one locus modifies the effects of alleles at one or more other loci

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.

the correct answer is option d.

an appositive is a noun, noun phrase or noun clause which follows another noun or noun phrase in order to describe it or name it another way. they are usually used between commas, brackets or dashes.

the example sentence with the correct use of commas is the following:

her uncle, the man over there in the red shirt, owns the hardware store in town.