| an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle. |
| an extraordinary or unusual thing, person, or event; an exceptional example or instance. |
| Stevens (stē'vənz) Pronunciation Key
American biologist who identified the role of X and Y chromosomes in determining the sex of an organism. Stevens studied the chromosomes of mealworm beetles, first establishing that chromosomes are inherited in pairs. She later showed that eggs fertilized by X-carrying sperm produced female offspring, while Y-carrying sperm produced male offspring. She extended this work to studies of sex determination in various plants and insects. |