Only the proteins that the bacteria Escherichia coli (E. coli) needs are synthesized at any given time. For example, when lactose is available in the environment, E. coli will express the lac genes that allow it to break down lactose to obtain energy. When lactose is not present, these genes are not expressed.

A microscopic image of E. coli.

Which prevents the lac genes in the DNA of E. coli from being expressed most of the time?
the lac repressor
the lac operator
the lac promoter
the lac locator

Aresearcher designed an investigation to test what effect eating different types of food would have on blood insulin levels. she selected 10 male subjects who were all 25 years of age and in good health. the experiment took place over 3 days. at 8: 00 a. m. on each day, the subjects ate a meal consisting of only 1 type of food. they had their blood insulin levels measured after consuming the meal. on day 1 they ate a high fat diet, on day 2 they ate a high protein diet, and on day 3 they ate a high sugar diel what is the independent variable in this experiment? a the age of the subjects b the blood insulin level c the type of food consumed d the time of day the meal was consumed

Imagine a self-reactive t cell that has not undergone clonal deletion in the thymus (that is to say, it has escaped central tolerance). if it encounters self antigen in the absence of an infection or inflammation, what will happen to this self-reactive t cell? (select two answers) (a) the t cell undergoes clonal expansion. (b) the t cell gains effector functions. (c) the t cell undergoes apoptosis. (d) the t cell becomes activated. (e) the t cell becomes anergic.

1. you serve a volleyball with a mass of 2.1 kg. the ball leaves your hand with a speed of 30 m/s. the ball has energy. calculate it. 2. a baby carriage is sitting at the top of a hill that is 21 m high. the carriage with the baby weighs 12 n. the carriage has energy. calculate it. 3. a car is traveling with a velocity of 40 m/s and has a mass of 1120 kg. the car has . calculate it.