The alternative splicing of the T-antigen gene of simian virus 40 (SV40) is regulated by the presence of splicing factor 2 (SF2), which is a(n) protein that contains two domains, an RNA-binding region and another domain with alternating serine and arginine amino acids.

Explanation:

Splicing is of two types: constitutive and alternative splicing

Alternative splicing produces different mRNA from the same pre-mRNA.

Splicing is a very tightly regulated process and involve various factors and enzyme. SR protein is a  serine /arginine-rich proteins, is a family of highly conserved splicing regulators that this is also involved in other steps like  in RNA biogenesis and expression. These SR proteins are necessary for viral RNA processing. SR protein contains two domains, i) an RNA-binding region and ii) another domain with alternating serine and arginine amino acids.

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.