How do cells repair themselves?

Asegment of dna that codes for rna and a protein is a

Ivan is looking at a cross section of a stem taken from a vascular plant. he sees two different types of vascular tissue: the xylem, which is closer to the center of the stem, and the phloem, located around the xylem, closer to the outside of the stem. how do these two structures work together in a living plant?

Why do mountaineers become breathless as they reach high altitudes