RNA polymerase 20. Cyclins were first characterized in early embryos of marine invertebrates like clams and starfish. The nucleus in G1 will begin replicating its DNA due to the action of a diffusible activator of DNA synthesis present in the cytoplasm of the S phase cell 24. Culture the cells in the presence of radioactive tyrosine for a brief period and then determine the proportion of cells that had incorporated label during that time 25. It is an inhibitor of reverse transcriptase, an enzyme required for retroviruses to replicate.
Retroviruses cause cancer and inhibiting their replication prevents ovarian and breast cancer.
Certain viruses, known as tumor viruses, have been shown to cause cancer when the virus infects a host animal or to cause transformation of tissue culture cells when the virus infects the cultured cells. Give a brief explanation for this phenomenon. Plant organelles called plasmodesmata that carry vesicles of cellulose, hemicellulose, and pectin to the boundary between the two daughter cells 30. Hyaluronic acid does not have sulfurs attached to the repeating disaccharides and forms much longer polymers than other glycosaminoglycans 31. Explain what chemical property of glycosaminoglycans causes them to attract large amounts of water to the matrix.