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.

explanation:

the fossil record extends back to a dog-like ancestor some 55 million years ago, which gave rise to the first horse-like species 55 to 42 million years ago in the genus eohippus.

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.