The hershey and chase experiments involved the preparation of two different types of radioactively labeled phage. which of the following best explains why two preparations were required?
a. the bacteriophage used in the experiments was a t2 phage.
b. it was necessary that each of the two phage components, dna and protein, be identifiable upon recovery at the end of the experiment.
c. each scientist had his own method for labeling phage, so each conducted the same experiment using a different isotope.
d. establishing the identity of the genetic material required observation of two phage generations.

B. It was necessary that each of the two phage components, DNA and protein, be identifiable upon recovery at the end of the experiment.

Explanation:

Hershey and Martha Chase used radiolabeled the DNA of some of the bacteriophage cells with phosphorus (32P). They radiolabeled the sulfur (35S) of the coat protein in the second batch of the phage cells. They infected some of the bacterial cells with phage having radiolabeled DNA while the other E. coli cells were infected with the phage carrying radiolabeled coat protein. This allowed the clear identification of the radiolabelled molecule (DNA or protein) present in the host cell.

They observed that the E. coli cells infected with phage having radiolabeled DNA exhibited the radioactivity while the other batch of the host cell did not show it.  

hormones in blood stream

image: dtc.ucsf.edu

endocrine glands secrete hormones into the blood stream near them; the hormones then travel in our bloodstream until it reaches its destination, called a target cell, in distance parts of the body. in the target tissue, hormones lock onto the target’s plasma membrane, called the receptor site.