"Hi, Sis!"

Mary Lou was especially excited this evening as she drove with her parents to the science fair presentations. Not only was she told that her group had made a rather momentous discovery, but - and this was even better - her parents were to meet Jimmy's parents for the first time. But this meeting was almost called off because Mary Lou's mother was to meet her long-lost sister at 8:30 that evening. This science fair thing had made the scheduling very tight.

Her brother Jason and his raggamuffin freshman friend Wilbie were very pleased to be helping Cheryl put up their poster, but it was dangerous work for the guys as they stuck themselves with tacks several times as they were entranced by being so close to their smart and beautiful classmate. This is what their poster was all about:

Wilbie had gotten Dr. Johannsson over at SynteX, across the road from their college, to help them radioactively label the E. coli cells in their culture with ₁₄C-thymidine. After the culture had grown many generations in this L-broth that had been dosed with this ₁₄C-thymidine, they "washed" the cells free of excess ₁₄C-thymidine by centrifuging them out of their old medium and resuspending the cells in new L-broth (with no new radioisotopes). They then followed the optical density of the culture as it continued to grow. Each time the culture had doubled (about each 20 minutes), they took a drop of the culture and put it on a microscope slide. After the water had evaporated away and the smudges were dry, the slides were taken into the dark room and a photographic emulsion (like on unexposed film) was spread as thin layers over the smudges, and these were allowed to dry in the dark. Then the slides were put into a light-tight box and stored over spring break. Upon returning, the slides were photographically developed, and inspected under the microscope. What they saw in the "zero-time" slide was that each cell had about 80 very small black dots of silver grains bunched together. After one generation, each cell had about 40 bunched dots. After two generations, the "AUTORADIOGRAPH" showed about half of the cells with 40 bunched dots, and the remaining cells with no dots. Thereafter, as the generations progressed, there were a few cells with 40 dots, and an ever-growing number of undotted cells.

Jimmy brought his parents over to meet his fiancee's parents, before taking them to the poster, where a large number of people had gathered. As Jason stood gazing at Cheryl, Wilbie nudged him to remind him that she was so much older than he was. "Maybe she is now - proportionately," Jason whispered back. Here's what the crowd was excited about:

When Jimmy's mother saw Mary Lou's mother, she stopped, tilted her head, and was about to say something when Mary Lou's mother screeched: "Sis, it's been so long!" Hugs and tears were aplenty.