Answer the following question given this paragraph: 

DNA replicates in the S phase of interphase. After replication, the chromosomes are composed of two linked sister chromatids. When fully compact, the pairs of identically packed chromosomes are bound to each other by cohesin proteins. The connection between the sister chromatids is closest in a region called the centromere. The conjoined sister chromatids, with a diameter of about 1 µm, are visible under a light microscope. The centromeric region is highly condensed and thus will appear as a constricted area.


Q: What replicates in the s phase of interphase, resulting in chromosomes composed of two linked sister chromatids?

 Choices:

- protein

- hormones

- RNA

- dna

A:
dna
