Which organ is responsible for training T-cells?

tonsils
appendix
spleen
thymus

Protein idk i dont have the book

Dna replication occurs during the s-phase of interphase. also known as prophase

Ibelieve the answer is that the sparrows have only one type of base in their cells; while robins have many types.  the five different types of bases found in living things are; uracil, thymine, guanine, adenine, and cytosine. thymine, guanine, adenine, cytosine are  normally found in the dna, while in the rna thymine is replaced by uracil.