The use of restriction enzymes as a way to cut DNA molecules was first demonstrated in a classic study by Johns Hopkins biochemist Daniel Nathans and his graduate student Kathleen Danna (Danna & Nathans, 1971).
Home : Climate Graphs: Pennsylvania : Philadelphia. Philadelphia's coldest month is January when the average temperature overnight is 25.5Â°F. In July, the warmest month, the average day time temperature rises to 85.5Â°F.
All-time Record Hottest Temperature Ever Recorded in Philadelphia is 106 Degrees. The hottest temperature ever officially recorded in the city of Philadelphia is 106 degrees, which occurred on August 7, 1918. Days when the temperature reaches or exceeds 100 degrees are not common in Philadelphia.