video1.0<iframe src="https://www.loom.com/embed/f3059499ce7b45339c692fd909c3ce8f" frameborder="0" width="1096" height="822" webkitallowfullscreen mozallowfullscreen allowfullscreen></iframe>8221096Loomhttps://www.loom.com8221096https://cdn.loom.com/sessions/thumbnails/f3059499ce7b45339c692fd909c3ce8f-00001.jpg136p: The authors use the word “backbone” in lines 3 and 39 to indicate that a: only very long chains of DNA can be taken from an organism with a spinal column. ; the main structure of a chain in a DNA molecule is composed of repeating units. ; a chain in a DNA molecule consists entirely of phosphate groups or of sugars. ; nitrogenous bases form the main structural unit of DNA. ;