Some E. coli mutants contain defective DNA ligase. When researchers expose these mutants to 3H-labeled thymine and then sediment the DNA produced on an alkaline sucrose density gradient, two radioactive bands appear. One corresponds to a high molecular weight fraction, the other to a low molecular weight fraction. Explain.

The bacteria found in a soil is usually harmful and measure are taken to remove any traces of microorganisms 1. true 2. false

What sentence best supports the statement that hormones are involved in the regulation of homeostasis? a. the hormone erythropoeitin increases the production of red blood cells when oxygen levels are low. b. the hormone oxytocin promotes labor contractions of the uterus during childbirth. c. the hormone melatonin induces sleep and its production is slowed by exposure to light. d. the hormone cortisol suppresses the immune system and is produced when the body is under stress.

Organelles found in plant cells that function through photosynthesis to produce glucose from carbon dioxide and water are called — question 21 options: chloroplasts guard cells photosynthons